A Review: Photonic Devices Used for Dosimetry in Medical Radiation
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paper_title: Radiation Detection and Measurement

paper_content:

Chapter 1 Radiation Sources. I. Units And Definitions. II. Fast Electron Sources. III. Heavy Charged Particle Sources. IV. Sources Of Electromagnetic Radiation. V. Neutron Sources. Chapter 2 Radiation Interactions. I. Interaction Of Heavy Charged Particles. II. Interaction Of Fast Electrons. III. Interaction Of Gamma Rays. IV. Interaction Of Neutrons. V. Radiation Exposure And Dose. Chapter 3 Counting Statistics And Error Prediction. I. Characterization Of Data. II. Statistical Models. III. Applications Of Statistical Models. IV. Error Propagation. V. Optimization Of Counting Experiments. VI. Limits Of Detectability. VII. Distribution Of Time Intervals. Chapter 4 General Properties Of Radiation Detectors. I. Simplified Detector Model. II. Modes Of Detector Operation. III. Pulse Height Spectra. IV. Counting Curves And Plateaus. V. Energy Resolution. VI. Detection Efficiency. VII. Dead Time. Chapter 5 Ionization Chambers. I. The Ionization Process In Gases. II. Charge Migration And Collection. III. Design And Operation Of Dc Ion Chambers. IV. Radiation Dose Measurement With Ion Chambers. V. Applications Of Dc Ion Chambers. VI. Pulse Mode Operation. Chapter 6 Proportional Counters. I. Gas Multiplication. II. Design Features Of Proportional Counters. III. Proportional Counter Performance. IV. Detection Efficiency And Counting Curves. V. Variants Of The Proportional Counter Design. VI. Micropattern Gas Detectors. Chapter 7 Geiger-Mueller Counters. I. The Geiger Discharge. II. Fill Gases. III. Quenching. IV. Time Behavior. V. The Geiger Counting Plateau. VI. Design Features. VII. Counting Efficiency. VIII. Time-To-First-Count Method. IX. G-M Survey Meters. Chapter 8 Scintillation Detector Principles. I. Organic Scintillators. II. Inorganic Scintillators. III. Light Collection And Scintillator Mounting. Chapter 9 Photomultiplier Tubes And Photodiodes. I. Introduction. II. The Photocathode. III. Electron Multiplication. IV. Photomultiplier Tube Characteristics. V. Ancillary Equipment Required With Photomultiplier Tubes. VI. Photodiodes As Substitutes For Photomultiplier Tubes. VII. Scintillation Pulse Shape Analysis. VIII. Hybrid Photomultiplier Tubes. IX. Position-Sensing Photomultiplier Tubes. X. Photoionization Detectors. Chapter 10 Radiation Spectroscopy With Scintillators. I. General Considerations In Gamma-Ray Spectroscopy. II. Gamma-Ray Interactions. III. Predicted Response Functions. IV. Properties Of Scintillation Gamma-Ray Spectrometers. V. Response Of Scintillation Detectors To Neutrons. VI. Electron Spectroscopy With Scintillators. VII. Specialized Detector Configurations Based On Scintillation. Chapter 11 Semiconductor Diode Detectors. I. Semiconductor Properties. II. The Action Of Ionizing Radiation In Semiconductors. III. Semiconductors As Radiation Detectors. IV. Semiconductor Detector Configurations. V. Operational Characteristics. VI. Applications Of Silicon Diode Detectors. Chapter 12 Germanium Gamma-Ray Detectors. I. General Considerations. II. Configurations Of Germanium Detectors. III. Germanium Detector Operational Characteristics. IV. Gamma-Ray Spectroscopy With Germanium Detectors. Chapter 13 Other Solid-State Detectors. I. Lithium-Drifted Silicon Detectors. II. Semiconductor Materials Other Than Silicon Or Germanium. III. Avalanche Detectors. IV. Photoconductive Detectors. V. Position-Sensitive Semiconductor Detectors. Chapter 14 Slow Neutron Detection Methods. I. Nuclear Reactions Of Interest In Neutron Detection. II. Detectors Based On The Boron Reaction. III. Detectors Based On Other Conversion Reactions. IV. Reactor Instrumentation. Chapter 15 Fast Neutron Detection And Spectroscopy. I. Counters Based On Neutron Moderation. II. Detectors Based On Fast Neutron-Induced Reactions. III. Detectors That Utilize Fast Neutron Scattering. Chapter 16 Pulse Processing. I. Overview Of Pulse Processing. II. Device Impedances. III. Coaxial Cables. IV. Linear And Logic Pulses. V. Instrument Standards. VI. Summary Of Pulse-Processing Units. VII. Application Specific Integrated Circuits (ASICS). VIII. Components Common To Many Applications. Chapter 17 Pulse Shaping, Counting, And Timing. I. Pulse Shaping. II. Pulse Counting Systems. III. Pulse Height Analysis Systems. IV. Digital Pulse Processing. V. Systems Involving Pulse Timing. VI. Pulse Shape Discrimination. Chapter 18 Multichannel Pulse Analysis. I. Single-Channel Methods. II. General Multichannel Characteristics. III. The Multichannel Analyzer. IV. Spectrum Stabilization And Relocation. V. Spectrum Analysis. Chapter 19 Miscellaneous Detector Types. I. Cherenkov Detectors. II. Gas-Filled Detectors In Self-Quenched Streamer Mode. III. High-Pressure Xenon Spectrometers. IV. Liquid Ionization And Proportional Counters. V. Cryogenic Detectors. VI. Photographic Emulsions. VII. Thermoluminescent Dosimeters And Image Plates. VIII. Track-Etch Detectors. IX. Superheated Drop Or "Bubble Detectors". X. Neutron Detection By Activation. XI. Detection Methods Based On Integrated Circuit Components. Chapter 20 Background And Detector Shielding. I. Sources Of Background. II. Background In Gamma-Ray Spectra. III. Background In Other Detectors. IV. Shielding Materials. V. Active Methods Of Background Reduction. Appendix A The NIM, CAMAC, And VME Instrumentation Standards. Appendix B Derivation Of The Expression For Sample Variance In Chapter 3. Appendix C Statistical Behavior Of Counting Data For Variable Mean Value. Appendix D The Shockley-Ramo Theorem For Induced Charge.
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paper_title: From photovoltaics to medical imaging: Applications of thin-film CdTe in x-ray detection

paper_content:

Recent developments in photovoltaics created a commercially viable technology of large area uniform thin-film structures, potentially extendable to the field of medical imaging, where the capability of producing large area x-ray detectors is essential for the successful diagnosis and treatment of cancer. We propose a large area thin-film CdTe structure suitable for radiation detection and discuss its main characteristics under x-ray beams used in radiation therapy. While based on the same principle, the details of its operations are very dissimilar from that of photovoltaics.
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paper_title: Application of a natural diamond detector for the measurement of relative dose distributions in radiotherapy

paper_content:

The suitability of a natural diamond detector with a special contact system for the measurement or relative dose distributions in selected radiotherapy applications was studied. The performance of the diamond detector was analysed by comparison with measurements using an ionization chamber and a silicon diode detector. The good stability, high response and good spatial resolution of the diamond detector were demonstrated by relative measurements in high energy photon and electron beams and around the 137Cs source of an afterloading device. The application of the diamond detectors for relative as well as absolute dose measurements of beta ray ophthalmic applicators was also highlighted. It is concluded that the diamond with the special contact system is a suitable detector for relative dose measurements in a wide variety of applications, especially when high response and high spatial resolution is required.
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paper_title: The Past, Present, and Future of Silicon Photonics

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The pace of the development of silicon photonics has quickened since 2004 due to investment by industry and government. Commercial state-of-the-art CMOS silicon-on-insulator (SOI) foundries are now being utilized in a crucial test of 1.55-mum monolithic optoelectronic (OE) integration, a test sponsored by the Defense Advanced Research Projects Agency (DARPA). The preliminary results indicate that the silicon photonics are truly CMOS compatible. RD however, lasing has not yet been attained. The new paradigm for the Si-based photonic and optoelectric integrated circuits is that these chip-scale networks, when suitably designed, will operate at a wavelength anywhere within the broad spectral range of 1.2-100 mum, with cryocooling needed in some cases
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paper_title: Development and evaluation of gallium nitride-based thin films for x-ray dosimetry.

paper_content:

X-ray radiation plays an important role in medical procedures ranging from diagnostics to therapeutics. Due to the harm such ionizing radiation can cause, it has become common practice to closely monitor the dosages received by patients. To this end, precise online dosimeters have been developed with the dual objectives of monitoring radiation in the region of interest and improving therapeutic methods. In this work, we evaluate GaN thin film high electron mobility heterostructures with sub-mm(2) detection areas as x-ray radiation detectors. Devices were tested using 40-300 kV Bremsstrahlung x-ray sources. We find that the photoconductive device response exhibits a large gain, is almost independent of the angle of irradiation, and is constant to within 2% of the signal throughout this medical diagnostic x-ray range, indicating that these sensors do not require recalibration for geometry or energy. Furthermore, the devices show a high sensitivity to x-ray intensity and can measure in the air kerma rate (free-in-air) range of 1 µGy s(-1) to 10 mGy s(-1) with a signal stability of ±1% and a linear total dose response over time. Medical conditions were simulated by measurements of device responses to irradiation through human torso phantoms. Direct x-ray imaging is demonstrated using the index finger and wrist sections of a human phantom. The results presented here indicate that GaN-based thin film devices exhibit a wide range of properties, which make them promising candidates for dosimetry applications. In addition, with potential detection volumes smaller than 10(-6) cm(3), they are well suited for high-resolution x-ray imaging. Moreover, with additional engineering steps, these devices can be adapted to potentially provide both in vivo biosensing and x-ray dosimetry.
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paper_title: Dosimetry of ionising radiation in modern radiation oncology

paper_content:

Dosimetry of ionising radiation is a well-established and mature branch of physical sciences with many applications in medicine and biology. In particular radiotherapy relies on dosimetry for optimisation of cancer treatment and avoidance of severe toxicity for patients. Several novel developments in radiotherapy have introduced new challenges for dosimetry with small and dynamically changing radiation fields being central to many of these applications such as stereotactic ablative body radiotherapy and intensity modulated radiation therapy. There is also an increasing awareness of low doses given to structures not in the target region and the associated risk of secondary cancer induction. Here accurate dosimetry is important not only for treatment optimisation but also for the generation of data that can inform radiation protection approaches in the future. The article introduces some of the challenges and highlights the interdependence of dosimetric calculations and measurements. Dosimetric concepts are explored in the context of six application fields: reference dosimetry, small fields, low dose out of field, in vivo dosimetry, brachytherapy and auditing of radiotherapy practice. Recent developments of dosimeters that can be used for these purposes are discussed using spatial resolution and number of dimensions for measurement as sorting criteria. While dosimetry is ever evolving to address the needs of advancing applications of radiation in medicine two fundamental issues remain: the accuracy of the measurement from a scientific perspective and the importance to link the measurement to a clinically relevant question. This review aims to provide an update on both of these.
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paper_title: Characterization of a low-cost PIN photodiode for dosimetry in diagnostic radiology.

paper_content:

A commercial silicon PIN-photodiode was tested and characterized as ionizing radiation detector for radiological applications. A current-to-voltage amplification stage was designed and realized in order to acquire the photodiode signal in current mode. The system was tested with clinical beams routinely used for radiography and mammography. A Monte Carlo simulation of the detector was performed with the MCNPX code in order to model and fully understand, in particular, the impact of the sensor casing on the low energy response of the device. A reproducible output linearity was found over the dose range 0.03-4.5 mGy of great clinical relevance. The system sensitivity was found to be stable at 0.2 V s Gy(-1) for effective X-ray energies between 17 and 40 keV. The batch-to-batch reproducibility of the diodes was also experimentally investigated for two different batches of 14 diodes each. An inter-comparison with dosimeters routinely used in medical physics (i.e. Barracuda MPD RTI) showed a linear correlation between PIN-photodiode readout and absorbed dose measured with Barracuda, in the range of doses received by mammography and radiology patients.
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paper_title: Silicon solar cells as a gamma ray dosimeter

paper_content:

Abstract Monocrystalline silicon solar cell of the construction n + pp ++ Passivated Emitter Solar Cell (PESC) irradiated by 60 Co gamma ray dose was studied. Thermoluminescence detectors (TLD) main dosimetry peak was investigated. The results showed that it is possible to determine gamma dose more accurate from TL main dosimetry peak for monocrystalline silicon solar cell in comparison with TLD (100). Also the various sources of uncertainty were analyzed. The expanded uncertainty at 95% confidence level should be added to the value of measurements to obtain accurate dose.
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paper_title: Radiation therapy dosimetry system.

paper_content:

New therapeutic treatments generally aim to increase therapeutic efficacy while minimizing toxicity. Many aspects of radiation dosimetry have been studied and developed particularly in the field of external radiation. The success of radiotherapy relies on monitoring the dose of radiation to which the tumor and the adjacent tissues are exposed. Radiotherapy techniques have evolved through a rapid transition from conventional three-dimensional (3D) conformal radiation therapy to intensity-modulated radiation therapy (IMRT) treatments or radiosurgery and robotic radiation therapy. These advances push the frontiers in our effort to provide better patient care by improving the precision of the absorbed dose delivered. This paper presents state-of-the art radiation therapy dosimetry techniques as well as the value of integral dosimetry (INDOS), which shows promise in the fulfillment of radiation therapy dosimetry requirements.
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paper_title: Temperature dependence of commercial 4H-SiC UV Schottky photodiodes for X-ray detection and spectroscopy

paper_content:

Two commercial-off-the-shelf (COTS) 4H-SiC UV photodiodes have been investigated for their suitability as low-cost high temperature tolerant X-ray detectors. Electrical characterisation of the photodiodes which had different active areas (0.06 mm² and 0.5 mm²) is reported over the temperature range 0 °C to 140 °C together with measurements of the X-ray photocurrents generated when the detectors were illuminated with an 55Fe radioisotope X-ray source. The 0.06 mm² photodiode was also investigated as a photon counting spectroscopic X-ray detector across the temperature range 0 °C to 100 °C. The depletion widths (at 120 V reverse bias) of the two diodes were found to be 2.3 µm and 4.5 µm, for the 0.06 mm² and 0.5 mm² detectors respectively, at 140 °C. Both devices had low leakage currents (<10 pA) at temperatures ≤40 °C even at high electric field strengths (500 kV/cm for 0.06 mm² diode; 267 kV/cm for 0.5 mm² diode). At 140 °C and similar field strengths (514 kV/cm for 0.06 mm² diode; 269 kV/cm for 0.5 mm2 diode), the leakage currents of both diodes were <2 nA (corresponding to leakage current densities of 2.4 µA/cm² and 0.3 µA/cm² for each diode respectively). The results demonstrated that both devices could function as current mode detectors of soft X-rays at the temperatures <80 °C and that when coupled to a low noise charge sensitive preamplifier, the smaller diode functioned as a photon counting spectroscopic X-ray detector at temperatures ≤100 °C with modest energy resolution (1.6 keV FWHM at 5.9 keV at 0 °C; 2.6 keV FWHM at 5.9 keV at 100 °C). Due to their temperature tolerance, wide commercial availability, and the radiation hardness of SiC, such detectors are expected to find utility in future low-cost nanosatellite (cubesat) missions and cost-sensitive industrial applications.
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paper_title: Characterization of Linear-mode Avalanche Photodiodes in Standard CMOS

paper_content:

Linear-mode Avalanche PhotoDiodes (APDs) can be fabricated in standard CMOS processes for obtaining high multiplication ga ins that allow to determine the number of incident photons with great precision. This idea can be exploited in several application domains, such as image sensors, optical communications and quantum information. In this work, we present a linearmode APD fabricated in a 0.35 μm CM OS process and report its noise characterization and gain. © 2014 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of Eurosensors 2014.
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paper_title: Current mode response of phototransistors to gamma radiation

paper_content:

Abstract This paper investigates the current mode response of four commercial NPN phototransistors under gamma radiation exposure from Co-60 source, with the aim to evaluate their applicability for gamma radiation dosimetry. The radiation-induced collector current was measured while the phototransistors were successively biased with 10 V and 20 V between collector and emitter. The main aspects analyzed in the experiment were the stability of the induced current, dependence of the induced current with respect to dose rate, short-term repeatability of the induced current and relation between the induced charge and the absorbed dose. The current response of all samples was stable during the 2-min irradiation sessions at the dose rates from 0.65 Gy/h to 32.1 Gy/h, with the relative uncertainty less than 5% in all cases, and the variation of the mean effective current as a function of dose rate was well fitted with the standard power relation. During the three consecutive 2-min irradiation sessions at the dose rate of 32.1 Gy/h, the repeatability of the induced charge was very good for all samples with the relative uncertainty below 3%. However, for continuous irradiation up to the absorbed dose of 20 Gy (10-min irradiation at the dose rate of 60 Gy/h), all samples exhibited significant current fall which can be attributed to the radiation-induced current gain degradation. As a result of the current degradation, the relationship between the induced charge and the absorbed dose was non-linear and it was demonstrated that the second order polynomial can be used as a calibration equation for determination of absorbed dose. The obtained results have shown that only one of the examined phototransistors may be a suitable candidate for gamma radiation dosimetry employing Co-60 source, since it has exhibited the highest current sensitivity, best linearity of the induced current with respect to dose rate and smallest dose rate dependence of the charge sensitivity.
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paper_title: Characterization of a low-cost PIN photodiode for dosimetry in diagnostic radiology.

paper_content:

A commercial silicon PIN-photodiode was tested and characterized as ionizing radiation detector for radiological applications. A current-to-voltage amplification stage was designed and realized in order to acquire the photodiode signal in current mode. The system was tested with clinical beams routinely used for radiography and mammography. A Monte Carlo simulation of the detector was performed with the MCNPX code in order to model and fully understand, in particular, the impact of the sensor casing on the low energy response of the device. A reproducible output linearity was found over the dose range 0.03-4.5 mGy of great clinical relevance. The system sensitivity was found to be stable at 0.2 V s Gy(-1) for effective X-ray energies between 17 and 40 keV. The batch-to-batch reproducibility of the diodes was also experimentally investigated for two different batches of 14 diodes each. An inter-comparison with dosimeters routinely used in medical physics (i.e. Barracuda MPD RTI) showed a linear correlation between PIN-photodiode readout and absorbed dose measured with Barracuda, in the range of doses received by mammography and radiology patients.
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paper_title: Absorbance measurements with light-emitting diodes as sources: Silicon photodiodes or light-emitting diodes as detectors?

paper_content:

Abstract Light-emitting diodes may also serve as light detectors, and the combination of two of these devices, one serving as light source, the other for detection, has been reported repeatedly for use in analytical photometry. A comparative study of the performance of light-emitting diodes in this role and that of a standard photodiode is reported herein. The spectral sensitivities of the light-emitting diodes were found to be as narrow as their emission bands, but shifted to shorter wavelengths, so that the spectral overlaps between emission and sensitivity of the same devices are very limited. The photocurrents of the light-emitting diodes were found to be about ten times lower than those of the photodiode. In the discharge mode (the time for discharge of the p/n-junction by the photocurrent is measured) as well as the photovoltaic mode, both of which had previously been reported for light-emitting diodes used as detectors in photometric devices, the performance of a light-emitting diode was on a level that is adequate for many analytical purposes, but the photodiode generally gave better precision and the signals showed faster settling times.
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paper_title: PiN photodiode performance comparison for dosimetry in radiology applications.

paper_content:

Performance comparison of selected photodiodes for usage as radiation detectors for radio-protection is presented. In this study, based on the criteria of minimum sensitive area of 5mm2, minimum half angle 60° and low cost, four commercial photodiodes are selected for evaluation: SFH205, SFH206, BPW34, and BPX90F. Photodiodes are low cost, small volume and lightweight detectors. As an electronic transducer, photodiode detector is an attractive approach for the development of low power portable electronic dosimeter for direct-reading real-time radiation dose measurement. The devices have been studied with respect to sensitivity (efficiency) in X-rays and gamma rays detection, repeatability and linearity in air kerma.
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paper_title: LEDs for lighting: Basic physics and prospects for energy savings

paper_content:

Abstract In 2014, Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura received the Nobel Prize in Physics for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”. Indeed, in the recent years, Light-Emitting Diodes (LEDs) have progressively made their way to the home lighting market, as well as to other mass markets. This article aims at giving an insight on LEDs physics, on the key inventions that led to the 2014 Nobel Prize and on the prospects for energy savings that LEDs could allow.
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paper_title: Absorbance Based Light Emitting Diode Optical Sensors and Sensing Devices

paper_content:

The ever increasing demand for in situ monitoring of health, environment and security has created a need for reliable, miniaturised sensing devices. To achieve this, appropriate analytical devices are required that possess operating characteristics of reliability, low power consumption, low cost, autonomous operation capability and compatibility with wireless communications systems. The use of light emitting diodes (LEDs) as light sources is one strategy, which has been successfully applied in chemical sensing. This paper summarises the development and advancement of LED based chemical sensors and sensing devices in terms of their configuration and application, with the focus on transmittance and reflectance absorptiometric measurements.
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paper_title: Temperature dependence of commercial 4H-SiC UV Schottky photodiodes for X-ray detection and spectroscopy

paper_content:

Two commercial-off-the-shelf (COTS) 4H-SiC UV photodiodes have been investigated for their suitability as low-cost high temperature tolerant X-ray detectors. Electrical characterisation of the photodiodes which had different active areas (0.06 mm² and 0.5 mm²) is reported over the temperature range 0 °C to 140 °C together with measurements of the X-ray photocurrents generated when the detectors were illuminated with an 55Fe radioisotope X-ray source. The 0.06 mm² photodiode was also investigated as a photon counting spectroscopic X-ray detector across the temperature range 0 °C to 100 °C. The depletion widths (at 120 V reverse bias) of the two diodes were found to be 2.3 µm and 4.5 µm, for the 0.06 mm² and 0.5 mm² detectors respectively, at 140 °C. Both devices had low leakage currents (<10 pA) at temperatures ≤40 °C even at high electric field strengths (500 kV/cm for 0.06 mm² diode; 267 kV/cm for 0.5 mm² diode). At 140 °C and similar field strengths (514 kV/cm for 0.06 mm² diode; 269 kV/cm for 0.5 mm2 diode), the leakage currents of both diodes were <2 nA (corresponding to leakage current densities of 2.4 µA/cm² and 0.3 µA/cm² for each diode respectively). The results demonstrated that both devices could function as current mode detectors of soft X-rays at the temperatures <80 °C and that when coupled to a low noise charge sensitive preamplifier, the smaller diode functioned as a photon counting spectroscopic X-ray detector at temperatures ≤100 °C with modest energy resolution (1.6 keV FWHM at 5.9 keV at 0 °C; 2.6 keV FWHM at 5.9 keV at 100 °C). Due to their temperature tolerance, wide commercial availability, and the radiation hardness of SiC, such detectors are expected to find utility in future low-cost nanosatellite (cubesat) missions and cost-sensitive industrial applications.
---
paper_title: Characterization of Linear-mode Avalanche Photodiodes in Standard CMOS

paper_content:

Linear-mode Avalanche PhotoDiodes (APDs) can be fabricated in standard CMOS processes for obtaining high multiplication ga ins that allow to determine the number of incident photons with great precision. This idea can be exploited in several application domains, such as image sensors, optical communications and quantum information. In this work, we present a linearmode APD fabricated in a 0.35 μm CM OS process and report its noise characterization and gain. © 2014 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of Eurosensors 2014.
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paper_title: Using RADFET for the real-time measurement of gamma radiation dose rate

paper_content:

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20 and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65 to 32.1 Gy h−1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose.
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paper_title: Current mode response of phototransistors to gamma radiation

paper_content:

Abstract This paper investigates the current mode response of four commercial NPN phototransistors under gamma radiation exposure from Co-60 source, with the aim to evaluate their applicability for gamma radiation dosimetry. The radiation-induced collector current was measured while the phototransistors were successively biased with 10 V and 20 V between collector and emitter. The main aspects analyzed in the experiment were the stability of the induced current, dependence of the induced current with respect to dose rate, short-term repeatability of the induced current and relation between the induced charge and the absorbed dose. The current response of all samples was stable during the 2-min irradiation sessions at the dose rates from 0.65 Gy/h to 32.1 Gy/h, with the relative uncertainty less than 5% in all cases, and the variation of the mean effective current as a function of dose rate was well fitted with the standard power relation. During the three consecutive 2-min irradiation sessions at the dose rate of 32.1 Gy/h, the repeatability of the induced charge was very good for all samples with the relative uncertainty below 3%. However, for continuous irradiation up to the absorbed dose of 20 Gy (10-min irradiation at the dose rate of 60 Gy/h), all samples exhibited significant current fall which can be attributed to the radiation-induced current gain degradation. As a result of the current degradation, the relationship between the induced charge and the absorbed dose was non-linear and it was demonstrated that the second order polynomial can be used as a calibration equation for determination of absorbed dose. The obtained results have shown that only one of the examined phototransistors may be a suitable candidate for gamma radiation dosimetry employing Co-60 source, since it has exhibited the highest current sensitivity, best linearity of the induced current with respect to dose rate and smallest dose rate dependence of the charge sensitivity.
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paper_title: Effect of heating rate on thermoluminescence output of LiF: Mg, Ti (TLD-100) in dosimetric applications

paper_content:

Abstract The luminiscence characteristics of thermoluminscence dosimeter LiF: Mg, Ti (TLD-100) irradiated to X-rays from 6 MV linac have been studied for wide range of 2–50 K/s readout linear heating rates. The reproducibility of glow curves for TLDs is found to be better at lower heating rates and depreciate at higher heating rates. The glow curve spectra were analysed using deconvolution procedure based on general-order kinetics. Shift in the peak maximum temperature per unit rise in heating rate for various peaks were found to decrease with heating rate. The TLDs irradiated with same dose exhibit decreasing TL counts with increase in the heating rate, which indicate the thermal quenching effect in TLD-100. The value of activation energy for each peak within the glow curve increases with heating rate. Calibration curves plotted for the dose range 0.4–1020 cGy exhibit decreasing slope with increasing readout heating rate. Corrections for temperature lag between the heating element and the dosimeter, and the effective heating rate (βeff) across the sample estimated using formulation proposed by Kitis and Tuyn and are found to be fairly applicable.
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paper_title: Optically stimulated luminescence (OSL) dosimetry in medicine

paper_content:

This paper reviews fundamental and practical aspects of optically stimulated luminescence (OSL) dosimetry pertaining to applications in medicine, having particularly in mind new researchers and medical physicists interested in gaining familiarity with the field. A basic phenomenological model for OSL is presented and the key processes affecting the outcome of an OSL measurement are discussed. Practical aspects discussed include stimulation modalities (continuous-wave OSL, pulsed OSL and linear modulation OSL), basic experimental setup, available OSL readers, optical fiber systems and basic properties of available OSL dosimeters. Finally, results from the recent literature on applications of OSL in radiotherapy, radiodiagnostics and heavy charged particle dosimetry are discussed in light of the theoretical and practical framework presented in this review. Open questions and future challenges in OSL dosimetry are highlighted as a guide to the research needed to further advance the field.
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paper_title: Silicon solar cells as a gamma ray dosimeter

paper_content:

Abstract Monocrystalline silicon solar cell of the construction n + pp ++ Passivated Emitter Solar Cell (PESC) irradiated by 60 Co gamma ray dose was studied. Thermoluminescence detectors (TLD) main dosimetry peak was investigated. The results showed that it is possible to determine gamma dose more accurate from TL main dosimetry peak for monocrystalline silicon solar cell in comparison with TLD (100). Also the various sources of uncertainty were analyzed. The expanded uncertainty at 95% confidence level should be added to the value of measurements to obtain accurate dose.
---
paper_title: PiN photodiode performance comparison for dosimetry in radiology applications.

paper_content:

Performance comparison of selected photodiodes for usage as radiation detectors for radio-protection is presented. In this study, based on the criteria of minimum sensitive area of 5mm2, minimum half angle 60° and low cost, four commercial photodiodes are selected for evaluation: SFH205, SFH206, BPW34, and BPX90F. Photodiodes are low cost, small volume and lightweight detectors. As an electronic transducer, photodiode detector is an attractive approach for the development of low power portable electronic dosimeter for direct-reading real-time radiation dose measurement. The devices have been studied with respect to sensitivity (efficiency) in X-rays and gamma rays detection, repeatability and linearity in air kerma.
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paper_title: An alternative method for using bipolar junction transistors as a radiation dosimetry detector in breast cancer treatment

paper_content:

Abstract Silicon photodetectors and MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) are frequently used devices for measuring ionizing radiation in health physics instrumentation. The Bipolar Junction Transistor (BJT) is not a typical device used as a detector for measuring some physical quantities in radiotherapy beams due to its loss of sensitivity to ionizing radiation, as a consequence of radiation damage in the silicon semiconductor substrate. Actually, the know-how of the BJT characteristic curves and its response to ionizing radiation leads us to suggest an alternative method to estimate the radiation dose value in breast cancer treatments. The BJT parameter to be evaluated before and after the irradiation procedure is the BJT amplification factor, also called DC gain β . In this work, the study was done using a BJT known as Darlington type, within an Alderson Rando anthropomorphic phantom. Darlington transistors have very high gain and this feature allowed that the BJT gain changes to be correlated with the dose of the radiation beam. The results indicate that this new method could be an alternative option to estimate the dose value in the phantom for measurements in breast cancer radiotherapy.
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paper_title: LEDs for lighting: Basic physics and prospects for energy savings

paper_content:

Abstract In 2014, Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura received the Nobel Prize in Physics for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”. Indeed, in the recent years, Light-Emitting Diodes (LEDs) have progressively made their way to the home lighting market, as well as to other mass markets. This article aims at giving an insight on LEDs physics, on the key inventions that led to the 2014 Nobel Prize and on the prospects for energy savings that LEDs could allow.
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paper_title: Low‐cost flexible thin‐film detector for medical dosimetry applications

paper_content:

The purpose of this study is to characterize dosimetric properties of thin film photovoltaic sensors as a platform for development of prototype dose verification equipment in radiotherapy. Towards this goal, flexible thin-film sensors of dose with embedded data acquisition electronics and wireless data transmission are prototyped and tested in kV and MV photon beams. Fundamental dosimetric properties are determined in view of a specific application to dose verification in multiple planes or curved surfaces inside a phantom. Uniqueness of the new thin-film sensors consists in their mechanical properties, low-power operation, and low-cost. They are thinner and more flexible than dosimetric films. In principle, each thin-film sensor can be fabricated in any size (mm2 – cm2 areas) and shape. Individual sensors can be put together in an array of sensors spreading over large areas and yet being light. Photovoltaic mode of charge collection (of electrons and holes) does not require external electric field applied to the sensor, and this implies simplicity of data acquisition electronics and low power operation. The prototype device used for testing consists of several thin film dose sensors, each of about 1.5 cm × 5 cm area, connected to simple readout electronics. Sensitivity of the sensors is determined per unit area and compared to EPID sensitivity, as well as other standard photodiodes. Each sensor independently measures dose and is based on commercially available flexible thin-film aSi photodiodes. Readout electronics consists of an ultra low-power microcontroller, radio frequency transmitter, and a low-noise amplification circuit implemented on a flexible printed circuit board. Detector output is digitized and transmitted wirelessly to an external host computer where it is integrated and processed. A megavoltage medical linear accelerator (Varian Tx) equipped with kilovoltage online imaging system and a Cobalt source are used to irradiate different thin-film detector sensors in a Solid Water phantom under various irradiation conditions. Different factors are considered in characterization of the device attributes: energies (80 kVp, 130 kVp, 6 MV, 15MV), dose rates (different ms × mA, 100–600 MU/min), total doses (0.1 cGy–500 cGy), depths (0.5 cm–20 cm), irradiation angles with respect to the detector surface (0°–180°), and IMRT tests (closed MLC, sweeping gap). The detector response to MV radiation is both linear with total dose (~1-400 cGy) and independent of dose rate (100–600 Mu/min). The sensitivity per unit area of thin-film sensors is lower than for aSi flat-panel detectors, but sufficient to acquire stable and accurate signals during irradiations. The proposed thin-film photodiode system has properties which make it promising for clinical dosimetry. Due to the mechanical flexibility of each sensor and readout electronics, low-cost, and wireless data acquisition, it could be considered for quality assurance (e.g., IMRT, mechanical linac QA), as well as real-time dose monitoring in challenging setup configurations, including large area and 3D detection (multiple planes or curved surfaces).
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paper_title: Temperature dependence of commercial 4H-SiC UV Schottky photodiodes for X-ray detection and spectroscopy

paper_content:

Two commercial-off-the-shelf (COTS) 4H-SiC UV photodiodes have been investigated for their suitability as low-cost high temperature tolerant X-ray detectors. Electrical characterisation of the photodiodes which had different active areas (0.06 mm² and 0.5 mm²) is reported over the temperature range 0 °C to 140 °C together with measurements of the X-ray photocurrents generated when the detectors were illuminated with an 55Fe radioisotope X-ray source. The 0.06 mm² photodiode was also investigated as a photon counting spectroscopic X-ray detector across the temperature range 0 °C to 100 °C. The depletion widths (at 120 V reverse bias) of the two diodes were found to be 2.3 µm and 4.5 µm, for the 0.06 mm² and 0.5 mm² detectors respectively, at 140 °C. Both devices had low leakage currents (<10 pA) at temperatures ≤40 °C even at high electric field strengths (500 kV/cm for 0.06 mm² diode; 267 kV/cm for 0.5 mm² diode). At 140 °C and similar field strengths (514 kV/cm for 0.06 mm² diode; 269 kV/cm for 0.5 mm2 diode), the leakage currents of both diodes were <2 nA (corresponding to leakage current densities of 2.4 µA/cm² and 0.3 µA/cm² for each diode respectively). The results demonstrated that both devices could function as current mode detectors of soft X-rays at the temperatures <80 °C and that when coupled to a low noise charge sensitive preamplifier, the smaller diode functioned as a photon counting spectroscopic X-ray detector at temperatures ≤100 °C with modest energy resolution (1.6 keV FWHM at 5.9 keV at 0 °C; 2.6 keV FWHM at 5.9 keV at 100 °C). Due to their temperature tolerance, wide commercial availability, and the radiation hardness of SiC, such detectors are expected to find utility in future low-cost nanosatellite (cubesat) missions and cost-sensitive industrial applications.
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paper_title: Current mode response of phototransistors to gamma radiation

paper_content:

Abstract This paper investigates the current mode response of four commercial NPN phototransistors under gamma radiation exposure from Co-60 source, with the aim to evaluate their applicability for gamma radiation dosimetry. The radiation-induced collector current was measured while the phototransistors were successively biased with 10 V and 20 V between collector and emitter. The main aspects analyzed in the experiment were the stability of the induced current, dependence of the induced current with respect to dose rate, short-term repeatability of the induced current and relation between the induced charge and the absorbed dose. The current response of all samples was stable during the 2-min irradiation sessions at the dose rates from 0.65 Gy/h to 32.1 Gy/h, with the relative uncertainty less than 5% in all cases, and the variation of the mean effective current as a function of dose rate was well fitted with the standard power relation. During the three consecutive 2-min irradiation sessions at the dose rate of 32.1 Gy/h, the repeatability of the induced charge was very good for all samples with the relative uncertainty below 3%. However, for continuous irradiation up to the absorbed dose of 20 Gy (10-min irradiation at the dose rate of 60 Gy/h), all samples exhibited significant current fall which can be attributed to the radiation-induced current gain degradation. As a result of the current degradation, the relationship between the induced charge and the absorbed dose was non-linear and it was demonstrated that the second order polynomial can be used as a calibration equation for determination of absorbed dose. The obtained results have shown that only one of the examined phototransistors may be a suitable candidate for gamma radiation dosimetry employing Co-60 source, since it has exhibited the highest current sensitivity, best linearity of the induced current with respect to dose rate and smallest dose rate dependence of the charge sensitivity.
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paper_title: LEDs for lighting: Basic physics and prospects for energy savings

paper_content:

Abstract In 2014, Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura received the Nobel Prize in Physics for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”. Indeed, in the recent years, Light-Emitting Diodes (LEDs) have progressively made their way to the home lighting market, as well as to other mass markets. This article aims at giving an insight on LEDs physics, on the key inventions that led to the 2014 Nobel Prize and on the prospects for energy savings that LEDs could allow.
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paper_title: Low‐cost flexible thin‐film detector for medical dosimetry applications

paper_content:

The purpose of this study is to characterize dosimetric properties of thin film photovoltaic sensors as a platform for development of prototype dose verification equipment in radiotherapy. Towards this goal, flexible thin-film sensors of dose with embedded data acquisition electronics and wireless data transmission are prototyped and tested in kV and MV photon beams. Fundamental dosimetric properties are determined in view of a specific application to dose verification in multiple planes or curved surfaces inside a phantom. Uniqueness of the new thin-film sensors consists in their mechanical properties, low-power operation, and low-cost. They are thinner and more flexible than dosimetric films. In principle, each thin-film sensor can be fabricated in any size (mm2 – cm2 areas) and shape. Individual sensors can be put together in an array of sensors spreading over large areas and yet being light. Photovoltaic mode of charge collection (of electrons and holes) does not require external electric field applied to the sensor, and this implies simplicity of data acquisition electronics and low power operation. The prototype device used for testing consists of several thin film dose sensors, each of about 1.5 cm × 5 cm area, connected to simple readout electronics. Sensitivity of the sensors is determined per unit area and compared to EPID sensitivity, as well as other standard photodiodes. Each sensor independently measures dose and is based on commercially available flexible thin-film aSi photodiodes. Readout electronics consists of an ultra low-power microcontroller, radio frequency transmitter, and a low-noise amplification circuit implemented on a flexible printed circuit board. Detector output is digitized and transmitted wirelessly to an external host computer where it is integrated and processed. A megavoltage medical linear accelerator (Varian Tx) equipped with kilovoltage online imaging system and a Cobalt source are used to irradiate different thin-film detector sensors in a Solid Water phantom under various irradiation conditions. Different factors are considered in characterization of the device attributes: energies (80 kVp, 130 kVp, 6 MV, 15MV), dose rates (different ms × mA, 100–600 MU/min), total doses (0.1 cGy–500 cGy), depths (0.5 cm–20 cm), irradiation angles with respect to the detector surface (0°–180°), and IMRT tests (closed MLC, sweeping gap). The detector response to MV radiation is both linear with total dose (~1-400 cGy) and independent of dose rate (100–600 Mu/min). The sensitivity per unit area of thin-film sensors is lower than for aSi flat-panel detectors, but sufficient to acquire stable and accurate signals during irradiations. The proposed thin-film photodiode system has properties which make it promising for clinical dosimetry. Due to the mechanical flexibility of each sensor and readout electronics, low-cost, and wireless data acquisition, it could be considered for quality assurance (e.g., IMRT, mechanical linac QA), as well as real-time dose monitoring in challenging setup configurations, including large area and 3D detection (multiple planes or curved surfaces).
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paper_title: From photovoltaics to medical imaging: Applications of thin-film CdTe in x-ray detection

paper_content:

Recent developments in photovoltaics created a commercially viable technology of large area uniform thin-film structures, potentially extendable to the field of medical imaging, where the capability of producing large area x-ray detectors is essential for the successful diagnosis and treatment of cancer. We propose a large area thin-film CdTe structure suitable for radiation detection and discuss its main characteristics under x-ray beams used in radiation therapy. While based on the same principle, the details of its operations are very dissimilar from that of photovoltaics.
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paper_title: Optical imaging as an expansion of nuclear medicine: Cerenkov-based luminescence vs fluorescence-based luminescence

paper_content:

Integration of optical imaging technologies can further strengthen the field of radioguided surgery. Rather than using two separate chemical entities to achieve this extension, hybrid imaging agents can be used that contain both radionuclear and optical properties. Two types of such hybrid imaging agents are available: (1) hybrid imaging agents generated by Cerenkov luminescence imaging (CLI) of β-emitters and (2) hybrid imaging agents that contain both a radioactive moiety and a fluorescent dye. One major challenge clinicians are now facing is to determine the potential value of these approaches. With this tutorial review we intend to clarify the differences between the two approaches and highlight the clinical potential of hybrid imaging during image-guided surgery applications.
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paper_title: Application of a natural diamond detector for the measurement of relative dose distributions in radiotherapy

paper_content:

The suitability of a natural diamond detector with a special contact system for the measurement or relative dose distributions in selected radiotherapy applications was studied. The performance of the diamond detector was analysed by comparison with measurements using an ionization chamber and a silicon diode detector. The good stability, high response and good spatial resolution of the diamond detector were demonstrated by relative measurements in high energy photon and electron beams and around the 137Cs source of an afterloading device. The application of the diamond detectors for relative as well as absolute dose measurements of beta ray ophthalmic applicators was also highlighted. It is concluded that the diamond with the special contact system is a suitable detector for relative dose measurements in a wide variety of applications, especially when high response and high spatial resolution is required.
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paper_title: Čerenkov radiation imaging as a method for quantitative measurements of beta particles in a microfluidic chip

paper_content:

This work proposes a novel method for quantitative imaging of radioactivity on microfluidic chips by using visible light emission from Cerenkov radiation. Cerenkov radiation is generated when charged particles travel through an optically transparent material with a velocity greater than that of light in that material. It has been observed at UCLA that microfluidic chips used for 18F-related radio-synthesis studies have shown unidentified visible light emissions. In this study, the origin of the light was investigated and its feasibility as a quantitative imaging source was tested.
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paper_title: Application of p-Channel Power VDMOSFET as a High Radiation Doses Sensor

paper_content:

This paper presents a comparative study of RADFETs and commercial p-channel power VDMOSFETs sensitivity to gamma-ray irradiation. Sensitivity was characterized by the threshold voltage shift determined from extrapolated linear region of transfer characteristics in saturation as a function of radiation dose. Sensitivity was followed in the dose range from 100 Gy to 500 Gy without and with $ + 10~\hbox{V}$ gate bias. Linear dependence between threshold voltage shift and radiation dose was established for components for which the gate bias during irradiation was $ + 10~\hbox{V}$ . Sensitivity of p-channel power VDMOSFETs is larger than the RADFETs, and it is a consequence of a larger concentration of fixed traps generated by gamma-ray irradiation. The mechanisms responsible for the threshold voltage shift during irradiation have been discussed as well. The fading of these components was also monitored at room temperature up to 24 hours and it was shown that it is larger in p-channel power VDMOSFETs then in RADFETs.
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paper_title: Using RADFET for the real-time measurement of gamma radiation dose rate

paper_content:

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20 and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65 to 32.1 Gy h−1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose.
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paper_title: Current mode response of phototransistors to gamma radiation

paper_content:

Abstract This paper investigates the current mode response of four commercial NPN phototransistors under gamma radiation exposure from Co-60 source, with the aim to evaluate their applicability for gamma radiation dosimetry. The radiation-induced collector current was measured while the phototransistors were successively biased with 10 V and 20 V between collector and emitter. The main aspects analyzed in the experiment were the stability of the induced current, dependence of the induced current with respect to dose rate, short-term repeatability of the induced current and relation between the induced charge and the absorbed dose. The current response of all samples was stable during the 2-min irradiation sessions at the dose rates from 0.65 Gy/h to 32.1 Gy/h, with the relative uncertainty less than 5% in all cases, and the variation of the mean effective current as a function of dose rate was well fitted with the standard power relation. During the three consecutive 2-min irradiation sessions at the dose rate of 32.1 Gy/h, the repeatability of the induced charge was very good for all samples with the relative uncertainty below 3%. However, for continuous irradiation up to the absorbed dose of 20 Gy (10-min irradiation at the dose rate of 60 Gy/h), all samples exhibited significant current fall which can be attributed to the radiation-induced current gain degradation. As a result of the current degradation, the relationship between the induced charge and the absorbed dose was non-linear and it was demonstrated that the second order polynomial can be used as a calibration equation for determination of absorbed dose. The obtained results have shown that only one of the examined phototransistors may be a suitable candidate for gamma radiation dosimetry employing Co-60 source, since it has exhibited the highest current sensitivity, best linearity of the induced current with respect to dose rate and smallest dose rate dependence of the charge sensitivity.
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paper_title: The use of Cerenkov radiation in the measurement of β-emitting radionuclides

paper_content:

Abstract Cerenkov radiation produced in an aqueous by s-emitting radionuclides of energy greater than 260 KeV has been investigated as a means of radioassay. Compared with liquid scintillation techniques sample preparation is simple volumes up 20 ml may be counted and the efficiency is unaffected by chemical quenching. Due to the low photon yield the method is only practicable for radionuclides emitting s-particles of energy >1 MeV. The detection efficiency has been studied as a function of s energy; representative values are 25 per cent for 32 P and 62 per cent for 106 Ru 106 Rh using a commercial liquid scintillation counter fitted with two photomultiplier tubes in a fast coincident circuit. Colour and ultraviolet quenching can be serious and methods of correcting for them have been studie; external standardization, decoloration and the use of ultra-violet filters are shown to be convenient techniques. The counting efficiency is improved by using quarts apparatus, incorporating wavelength shifters and (because of the directional nature of Cerenkov radiation) by using a non-coincidence circuit.
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paper_title: Cherenkov imaging for linac beam shape analysis as a remote electronic quality assessment verification tool

paper_content:

PURPOSE ::: A remote imaging system tracking Cherenkov emission was analyzed to verify that the linear accelerator (linac) beam shape could be quantitatively measured at the irradiation surface for Quality Audit (QA). ::: ::: ::: METHODS ::: The Cherenkov camera recorded 2D dose images delivered on a solid acrylonitrile butadiene styrene (ABS) plastic phantom surface for a range of square beam sizes, and 6 MV photons. Imaging was done at source to surface distance (SSD) of 100 cm and compared to GaF film images and linac light fields of the same beam sizes, ranging over 5 × 5 cm2 up to 20 × 20 cm2 . Line profiles of each field were compared in both X and Y jaw directions. Each measurement was repeated on two different Clinac2100 machines. An interreader comparison of the beam width interpretation was completed using procedures commonly employed for beam to light field coincidence verification. Cherenkov measurements are also done for beams of complex treatment plan and isocenter QA. ::: ::: ::: RESULTS ::: The Cherenkov image widths matched with the measured GaF images and light field images, with accuracy in the range of ±1 mm standard deviation. The differences between the measurements were minor and within tolerance of geometrical requirement of standard linac QA procedures conducted by human setup verification, which had a similar error range. The measurement made by the remote imaging system allowed for beam shape extraction of radiation fields at the SSD location of the beam. ::: ::: ::: CONCLUSIONS ::: The proposed Cherenkov image acquisition system provides a valid way to remotely confirm radiation field sizes and provides similar information to that obtained from the linac light field or GaF film estimates of the beam size. The major benefit of this approach is that with a fixed installation of the camera, testing could be done completely under software control with automated image analysis, potentially simplifying conventional QA procedures with appropriate calibration of boundary definitions, and the natural extension to capturing dynamic treatment beamlets at SSD could have future value, such as verification of beam plans with complex beam shapes, like IMRT or "star-shot" QA for the isocenter.
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paper_title: Solar Cells: In Research and Applications—A Review

paper_content:

The light from the Sun is a non-vanishing renewable source of energy which is free from environmental pollution and noise. It can easily compensate the energy drawn from the non-renewable sources of energy such as fossil fuels and petroleum deposits inside the earth. The fabrication of solar cells has passed through a large number of improvement steps from one generation to another. Silicon based solar cells were the first generation solar cells grown on Si wafers, mainly single crystals. Further development to thin films, dye sensitized solar cells and organic solar cells enhanced the cell efficiency. The development is basically hindered by the cost and efficiency. In order to choose the right solar cell for a specific geographic location, we are required to understand fundamental mechanisms and functions of several solar technologies that are widely studied. In this article, we have reviewed a progressive development in the solar cell research from one generation to other, and discussed about their future trends and aspects. The article also tries to emphasize the various practices and methods to promote the benefits of solar energy.
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paper_title: Development and evaluation of gallium nitride-based thin films for x-ray dosimetry.

paper_content:

X-ray radiation plays an important role in medical procedures ranging from diagnostics to therapeutics. Due to the harm such ionizing radiation can cause, it has become common practice to closely monitor the dosages received by patients. To this end, precise online dosimeters have been developed with the dual objectives of monitoring radiation in the region of interest and improving therapeutic methods. In this work, we evaluate GaN thin film high electron mobility heterostructures with sub-mm(2) detection areas as x-ray radiation detectors. Devices were tested using 40-300 kV Bremsstrahlung x-ray sources. We find that the photoconductive device response exhibits a large gain, is almost independent of the angle of irradiation, and is constant to within 2% of the signal throughout this medical diagnostic x-ray range, indicating that these sensors do not require recalibration for geometry or energy. Furthermore, the devices show a high sensitivity to x-ray intensity and can measure in the air kerma rate (free-in-air) range of 1 µGy s(-1) to 10 mGy s(-1) with a signal stability of ±1% and a linear total dose response over time. Medical conditions were simulated by measurements of device responses to irradiation through human torso phantoms. Direct x-ray imaging is demonstrated using the index finger and wrist sections of a human phantom. The results presented here indicate that GaN-based thin film devices exhibit a wide range of properties, which make them promising candidates for dosimetry applications. In addition, with potential detection volumes smaller than 10(-6) cm(3), they are well suited for high-resolution x-ray imaging. Moreover, with additional engineering steps, these devices can be adapted to potentially provide both in vivo biosensing and x-ray dosimetry.
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paper_title: Optical imaging of Cerenkov light generation from positron-emitting radiotracers.

paper_content:

Radiotracers labeled with high-energy positron emitters, such as those commonly used for positron emission tomography studies, emit visible light immediately following decay in a medium. This phenomenon, not previously described for these imaging tracers, is consistent with Cerenkov radiation and has several potential applications, especially for in vivo molecular imaging studies. Herein we detail a new molecular imaging tool, Cerenkov Luminescence Imaging, the experiments conducted that support our interpretation of the source of the signal, and proof-of-concept in vivo studies that set the foundation for future application of this new method.
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paper_title: Photons across medicine: relating optical and nuclear imaging.

paper_content:

The Optics in the Life Sciences conference sponsored by the Optical Society of America was held in Waikoloa Beach, HI on April 14 – 18, 2013. Papers were presented in the areas of Bio-Optics: Design & Application, Novel Techniques in Microscopy, Optical Molecular Probes, Imaging & Drug Delivery, and Optical Trapping Applications. A focal point of the meeting was a special symposium entitled “Photons Across Medicine”, organized by Adam Wax, Duke University, highlighting activities of joint interest between the Optical Society of America (OSA) and the Society for Nuclear Medicine and Molecular Imaging (SNMMI). This paper is a synopsis of the presentations made at this joint symposium. Central to the special symposium presentations was the fact that the optical and nuclear imaging communities share common interests and challenges. These are highlighted in this article. Also discussed was the fact that the nuclear technologies in imaging have found their way into general clinical utility, a feat that has yet to be achieved by optical methods. Because of the common ground shared by the two technologies, coordination between the two societies should be planned.
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paper_title: Review of biomedical Čerenkov luminescence imaging applications

paper_content:

Cerenkov radiation is a fascinating optical signal, which has been exploited for unique diagnostic biological sensing and imaging, with significantly expanded use just in the last half decade. Cerenkov Luminescence Imaging (CLI) has desirable capabilities for niche applications, using specially designed measurement systems that report on radiation distributions, radiotracer and nanoparticle concentrations, and are directly applied to procedures such as medicine assessment, endoscopy, surgery, quality assurance and dosimetry. When compared to the other imaging tools such as PET and SPECT, CLI can have the key advantage of lower cost, higher throughput and lower imaging time. CLI can also provide imaging and dosimetry information from both radioisotopes and linear accelerator irradiation. The relatively short range of optical photon transport in tissue means that direct Cerenkov luminescence imaging is restricted to small animals or near surface human use. Use of Cerenkov-excitation for additional molecular probes, is now emerging as a key tool for biosensing or radiosensitization. This review evaluates these new improvements in CLI for both medical value and biological insight.
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paper_title: Čerenkov radiation, and its applications

paper_content:

The paper opens with a brief review of the original discovery of the radiation and the physical principles of the process that gives rise to it. This is followed by an elementary account of the theory of the effect. A general survey of the practical applications to cosmic-ray and high-energy physics is then presented, with two examples of modern detectors discussed in greater detail. The article concludes with an account of recent experiments carried out on light pulses from the night-sky associated with cosmic-ray showers, found to be due to Cerenkov radiation in the atmosphere.
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paper_title: Experimental analysis of a novel and low-cost pin photodiode dosimetry system for diagnostic radiology

paper_content:

Silicon PIN photodiode has recently found broad and exciting applications in the ionizing radiation dosimetry. In this study a compact and novel dosimetry system using a commercially available PIN photodiode (BPW34) has been experimentally tested for diagnostic radiology. The system was evaluated with clinical beams routinely used for diagnostic radiology and calibrated using a secondary reference standard. Measured dose with PIN photodiode (Air Kerma) varied from 10 to 430 μGy for tube voltages from 40 to 100 kVp and tube current from 0.4 to 40 mAs. The minimum detectable organ dose was estimated to be 10 μGy with 20% uncertainty. Results showed a linear correlation between the PIN photodiode readout and dose measured with standard dosimeters spanning doses received. The present dosimetry system having advantages of suitable sensitivity with immediate readout of dose values, low cost, and portability could be used as an alternative to passive dosimetry system such as thermoluminescent dosimeter for dose ...
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paper_title: Characterization of a low-cost PIN photodiode for dosimetry in diagnostic radiology.

paper_content:

A commercial silicon PIN-photodiode was tested and characterized as ionizing radiation detector for radiological applications. A current-to-voltage amplification stage was designed and realized in order to acquire the photodiode signal in current mode. The system was tested with clinical beams routinely used for radiography and mammography. A Monte Carlo simulation of the detector was performed with the MCNPX code in order to model and fully understand, in particular, the impact of the sensor casing on the low energy response of the device. A reproducible output linearity was found over the dose range 0.03-4.5 mGy of great clinical relevance. The system sensitivity was found to be stable at 0.2 V s Gy(-1) for effective X-ray energies between 17 and 40 keV. The batch-to-batch reproducibility of the diodes was also experimentally investigated for two different batches of 14 diodes each. An inter-comparison with dosimeters routinely used in medical physics (i.e. Barracuda MPD RTI) showed a linear correlation between PIN-photodiode readout and absorbed dose measured with Barracuda, in the range of doses received by mammography and radiology patients.
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paper_title: Silicon solar cells as a gamma ray dosimeter

paper_content:

Abstract Monocrystalline silicon solar cell of the construction n + pp ++ Passivated Emitter Solar Cell (PESC) irradiated by 60 Co gamma ray dose was studied. Thermoluminescence detectors (TLD) main dosimetry peak was investigated. The results showed that it is possible to determine gamma dose more accurate from TL main dosimetry peak for monocrystalline silicon solar cell in comparison with TLD (100). Also the various sources of uncertainty were analyzed. The expanded uncertainty at 95% confidence level should be added to the value of measurements to obtain accurate dose.
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paper_title: Evaluation of the applicability of MOSFET detectors in radiotherapy

paper_content:

Abstract MOSFET detectors of 1 mVcGy−1 sensitivity were tested for the accuracy of absorbed dose measurements in radiation therapy with the use of photon and electron beams. Before a detector was used in the study, several calibration coefficients were determined to allow for different factors affecting its operation. Then, the detector exposure response was compared with the dose calculated in the anthropomorphic phantom by the Monaco and MasterPlan treatment planning systems. MOSFET detectors were placed inside the phantom during the irradiation. Three different plans for thorax and pelvis areas were studied. The paper presents the differences between planned and MOSFET measured doses delivered to the selected target areas using conventional and IMRT techniques.
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paper_title: Real-time Cherenkov emission portal imaging during CyberKnife®radiotherapy

paper_content:

The feasibility of real-time portal imaging during radiation therapy, through the Cherenkov emission (CE) effect is investigated via a medical linear accelerator (CyberKnife®) irradiating a partially-filled water tank with a 60 mm circular beam. A graticule of lead/plywood and a number of tissue equivalent materials were alternatively placed at the beam entrance face while the induced CE at the exit face was imaged using a gated electron-multiplying-intensified-charged-coupled device (emICCD) for both stationary and dynamic scenarios. This was replicated on an Elekta Synergy® linear accelerator with portal images acquired using the iViewGT™ system. Profiles across the acquired portal images were analysed to reveal the potential resolution and contrast limits of this novel CE based portal imaging technique and compared against the current standard. The CE resolution study revealed that using the lead/plywood graticule, separations down to 3.4 ± 0.5 mm can be resolved. A 28 mm thick tissue-equivalent rod with electron density of 1.69 relative to water demonstrated a CE contrast of 15% through air and 14% through water sections, as compared to a corresponding contrast of 19% and 12% using the iViewGT™ system. For dynamic scenarios, video rate imaging with 30 frames per second was achieved. It is demonstrated that CE-based portal imaging is feasible to identify both stationary and dynamic objects within a CyberKnife® radiotherapy treatment field.
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paper_title: PiN photodiode performance comparison for dosimetry in radiology applications.

paper_content:

Performance comparison of selected photodiodes for usage as radiation detectors for radio-protection is presented. In this study, based on the criteria of minimum sensitive area of 5mm2, minimum half angle 60° and low cost, four commercial photodiodes are selected for evaluation: SFH205, SFH206, BPW34, and BPX90F. Photodiodes are low cost, small volume and lightweight detectors. As an electronic transducer, photodiode detector is an attractive approach for the development of low power portable electronic dosimeter for direct-reading real-time radiation dose measurement. The devices have been studied with respect to sensitivity (efficiency) in X-rays and gamma rays detection, repeatability and linearity in air kerma.
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paper_title: An alternative method for using bipolar junction transistors as a radiation dosimetry detector in breast cancer treatment

paper_content:

Abstract Silicon photodetectors and MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) are frequently used devices for measuring ionizing radiation in health physics instrumentation. The Bipolar Junction Transistor (BJT) is not a typical device used as a detector for measuring some physical quantities in radiotherapy beams due to its loss of sensitivity to ionizing radiation, as a consequence of radiation damage in the silicon semiconductor substrate. Actually, the know-how of the BJT characteristic curves and its response to ionizing radiation leads us to suggest an alternative method to estimate the radiation dose value in breast cancer treatments. The BJT parameter to be evaluated before and after the irradiation procedure is the BJT amplification factor, also called DC gain β . In this work, the study was done using a BJT known as Darlington type, within an Alderson Rando anthropomorphic phantom. Darlington transistors have very high gain and this feature allowed that the BJT gain changes to be correlated with the dose of the radiation beam. The results indicate that this new method could be an alternative option to estimate the dose value in the phantom for measurements in breast cancer radiotherapy.
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paper_title: Application of commercial MOSFET detectors for in vivo dosimetry in the therapeutic x-ray range from 80 kV to 250 kV

paper_content:

The purpose of this study was to investigate the dosimetric characteristics (energy dependence, linearity, fading, reproducibility, etc) of MOSFET detectors for in vivo dosimetry in the kV x-ray range. The experience of MOSFET in vivo dosimetry in a pre-clinical study using the Alderson phantom and in clinical practice is also reported. All measurements were performed with a Gulmay D3300 kV unit and TN-502RDI MOSFET detectors. For the determination of correction factors different solid phantoms and a calibrated Farmer-type chamber were used. The MOSFET signal was linear with applied dose in the range from 0.2 to 2 Gy for all energies. Due to fading it is recommended to read the MOSFET signal during the first 15 min after irradiation. For long time intervals between irradiation and readout the fading can vary largely with the detector. The temperature dependence of the detector signal was small (0.3% °C−1) in the temperature range between 22 and 40 °C. The variation of the measuring signal with beam incidence amounts to ±5% and should be considered in clinical applications. Finally, for entrance dose measurements energy-dependent calibration factors, correction factors for field size and irradiated cable length were applied. The overall accuracy, for all measurements, was dominated by reproducibility as a function of applied dose. During the pre-clinical in vivo study, the agreement between MOSFET and TLD measurements was well within 3%. The results of MOSFET measurements, to determine the dosimetric characteristics as well as clinical applications, showed that MOSFET detectors are suitable for in vivo dosimetry in the kV range. However, some energy-dependent dosimetry effects need to be considered and corrected for. Due to reproducibility effects at low dose levels accurate in vivo measurements are only possible if the applied dose is equal to or larger than 2 Gy.
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paper_title: Using RADFET for the real-time measurement of gamma radiation dose rate

paper_content:

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20 and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65 to 32.1 Gy h−1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose.
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paper_title: Current mode response of phototransistors to gamma radiation

paper_content:

Abstract This paper investigates the current mode response of four commercial NPN phototransistors under gamma radiation exposure from Co-60 source, with the aim to evaluate their applicability for gamma radiation dosimetry. The radiation-induced collector current was measured while the phototransistors were successively biased with 10 V and 20 V between collector and emitter. The main aspects analyzed in the experiment were the stability of the induced current, dependence of the induced current with respect to dose rate, short-term repeatability of the induced current and relation between the induced charge and the absorbed dose. The current response of all samples was stable during the 2-min irradiation sessions at the dose rates from 0.65 Gy/h to 32.1 Gy/h, with the relative uncertainty less than 5% in all cases, and the variation of the mean effective current as a function of dose rate was well fitted with the standard power relation. During the three consecutive 2-min irradiation sessions at the dose rate of 32.1 Gy/h, the repeatability of the induced charge was very good for all samples with the relative uncertainty below 3%. However, for continuous irradiation up to the absorbed dose of 20 Gy (10-min irradiation at the dose rate of 60 Gy/h), all samples exhibited significant current fall which can be attributed to the radiation-induced current gain degradation. As a result of the current degradation, the relationship between the induced charge and the absorbed dose was non-linear and it was demonstrated that the second order polynomial can be used as a calibration equation for determination of absorbed dose. The obtained results have shown that only one of the examined phototransistors may be a suitable candidate for gamma radiation dosimetry employing Co-60 source, since it has exhibited the highest current sensitivity, best linearity of the induced current with respect to dose rate and smallest dose rate dependence of the charge sensitivity.
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paper_title: Optically stimulated luminescence (OSL) dosimetry in medicine

paper_content:

This paper reviews fundamental and practical aspects of optically stimulated luminescence (OSL) dosimetry pertaining to applications in medicine, having particularly in mind new researchers and medical physicists interested in gaining familiarity with the field. A basic phenomenological model for OSL is presented and the key processes affecting the outcome of an OSL measurement are discussed. Practical aspects discussed include stimulation modalities (continuous-wave OSL, pulsed OSL and linear modulation OSL), basic experimental setup, available OSL readers, optical fiber systems and basic properties of available OSL dosimeters. Finally, results from the recent literature on applications of OSL in radiotherapy, radiodiagnostics and heavy charged particle dosimetry are discussed in light of the theoretical and practical framework presented in this review. Open questions and future challenges in OSL dosimetry are highlighted as a guide to the research needed to further advance the field.
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paper_title: Characterization of a low-cost PIN photodiode for dosimetry in diagnostic radiology.

paper_content:

A commercial silicon PIN-photodiode was tested and characterized as ionizing radiation detector for radiological applications. A current-to-voltage amplification stage was designed and realized in order to acquire the photodiode signal in current mode. The system was tested with clinical beams routinely used for radiography and mammography. A Monte Carlo simulation of the detector was performed with the MCNPX code in order to model and fully understand, in particular, the impact of the sensor casing on the low energy response of the device. A reproducible output linearity was found over the dose range 0.03-4.5 mGy of great clinical relevance. The system sensitivity was found to be stable at 0.2 V s Gy(-1) for effective X-ray energies between 17 and 40 keV. The batch-to-batch reproducibility of the diodes was also experimentally investigated for two different batches of 14 diodes each. An inter-comparison with dosimeters routinely used in medical physics (i.e. Barracuda MPD RTI) showed a linear correlation between PIN-photodiode readout and absorbed dose measured with Barracuda, in the range of doses received by mammography and radiology patients.
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paper_title: Comparative Study of Gamma and Neutron Irradiation Effects on the Silicon Solar Cells Parameters

paper_content:

Due to its wide application areas, solar cells are exposed, in their work environment, to different types of radiation (cosmic radiation in the upper layers of the atmosphere, military and civilian nuclear facilities). Moreover, the used nuclear fuel emits y photons and neutrons at the same time, so different types of radiation damage appeared in solar cells located in the vicinity of these fuels. These damage have been caused by both gamma and neutron radiation. That's why very extensive researches have been undertaken with the aim of developing semiconductor devices whose work will be reliable in terms of increased levels of radiation. From the technological point of view, it is important to determine changes, caused by radiation, in the parameters of the silicon solar cells that affect their work. The aim of this paper is to present the comparative study of gamma and neutron irradiation effects on the solar cells parameters.
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paper_title: PiN photodiode performance comparison for dosimetry in radiology applications.

paper_content:

Performance comparison of selected photodiodes for usage as radiation detectors for radio-protection is presented. In this study, based on the criteria of minimum sensitive area of 5mm2, minimum half angle 60° and low cost, four commercial photodiodes are selected for evaluation: SFH205, SFH206, BPW34, and BPX90F. Photodiodes are low cost, small volume and lightweight detectors. As an electronic transducer, photodiode detector is an attractive approach for the development of low power portable electronic dosimeter for direct-reading real-time radiation dose measurement. The devices have been studied with respect to sensitivity (efficiency) in X-rays and gamma rays detection, repeatability and linearity in air kerma.
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paper_title: Low‐cost flexible thin‐film detector for medical dosimetry applications

paper_content:

The purpose of this study is to characterize dosimetric properties of thin film photovoltaic sensors as a platform for development of prototype dose verification equipment in radiotherapy. Towards this goal, flexible thin-film sensors of dose with embedded data acquisition electronics and wireless data transmission are prototyped and tested in kV and MV photon beams. Fundamental dosimetric properties are determined in view of a specific application to dose verification in multiple planes or curved surfaces inside a phantom. Uniqueness of the new thin-film sensors consists in their mechanical properties, low-power operation, and low-cost. They are thinner and more flexible than dosimetric films. In principle, each thin-film sensor can be fabricated in any size (mm2 – cm2 areas) and shape. Individual sensors can be put together in an array of sensors spreading over large areas and yet being light. Photovoltaic mode of charge collection (of electrons and holes) does not require external electric field applied to the sensor, and this implies simplicity of data acquisition electronics and low power operation. The prototype device used for testing consists of several thin film dose sensors, each of about 1.5 cm × 5 cm area, connected to simple readout electronics. Sensitivity of the sensors is determined per unit area and compared to EPID sensitivity, as well as other standard photodiodes. Each sensor independently measures dose and is based on commercially available flexible thin-film aSi photodiodes. Readout electronics consists of an ultra low-power microcontroller, radio frequency transmitter, and a low-noise amplification circuit implemented on a flexible printed circuit board. Detector output is digitized and transmitted wirelessly to an external host computer where it is integrated and processed. A megavoltage medical linear accelerator (Varian Tx) equipped with kilovoltage online imaging system and a Cobalt source are used to irradiate different thin-film detector sensors in a Solid Water phantom under various irradiation conditions. Different factors are considered in characterization of the device attributes: energies (80 kVp, 130 kVp, 6 MV, 15MV), dose rates (different ms × mA, 100–600 MU/min), total doses (0.1 cGy–500 cGy), depths (0.5 cm–20 cm), irradiation angles with respect to the detector surface (0°–180°), and IMRT tests (closed MLC, sweeping gap). The detector response to MV radiation is both linear with total dose (~1-400 cGy) and independent of dose rate (100–600 Mu/min). The sensitivity per unit area of thin-film sensors is lower than for aSi flat-panel detectors, but sufficient to acquire stable and accurate signals during irradiations. The proposed thin-film photodiode system has properties which make it promising for clinical dosimetry. Due to the mechanical flexibility of each sensor and readout electronics, low-cost, and wireless data acquisition, it could be considered for quality assurance (e.g., IMRT, mechanical linac QA), as well as real-time dose monitoring in challenging setup configurations, including large area and 3D detection (multiple planes or curved surfaces).
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paper_title: Radiation Detection and Measurement

paper_content:

Chapter 1 Radiation Sources. I. Units And Definitions. II. Fast Electron Sources. III. Heavy Charged Particle Sources. IV. Sources Of Electromagnetic Radiation. V. Neutron Sources. Chapter 2 Radiation Interactions. I. Interaction Of Heavy Charged Particles. II. Interaction Of Fast Electrons. III. Interaction Of Gamma Rays. IV. Interaction Of Neutrons. V. Radiation Exposure And Dose. Chapter 3 Counting Statistics And Error Prediction. I. Characterization Of Data. II. Statistical Models. III. Applications Of Statistical Models. IV. Error Propagation. V. Optimization Of Counting Experiments. VI. Limits Of Detectability. VII. Distribution Of Time Intervals. Chapter 4 General Properties Of Radiation Detectors. I. Simplified Detector Model. II. Modes Of Detector Operation. III. Pulse Height Spectra. IV. Counting Curves And Plateaus. V. Energy Resolution. VI. Detection Efficiency. VII. Dead Time. Chapter 5 Ionization Chambers. I. The Ionization Process In Gases. II. Charge Migration And Collection. III. Design And Operation Of Dc Ion Chambers. IV. Radiation Dose Measurement With Ion Chambers. V. Applications Of Dc Ion Chambers. VI. Pulse Mode Operation. Chapter 6 Proportional Counters. I. Gas Multiplication. II. Design Features Of Proportional Counters. III. Proportional Counter Performance. IV. Detection Efficiency And Counting Curves. V. Variants Of The Proportional Counter Design. VI. Micropattern Gas Detectors. Chapter 7 Geiger-Mueller Counters. I. The Geiger Discharge. II. Fill Gases. III. Quenching. IV. Time Behavior. V. The Geiger Counting Plateau. VI. Design Features. VII. Counting Efficiency. VIII. Time-To-First-Count Method. IX. G-M Survey Meters. Chapter 8 Scintillation Detector Principles. I. Organic Scintillators. II. Inorganic Scintillators. III. Light Collection And Scintillator Mounting. Chapter 9 Photomultiplier Tubes And Photodiodes. I. Introduction. II. The Photocathode. III. Electron Multiplication. IV. Photomultiplier Tube Characteristics. V. Ancillary Equipment Required With Photomultiplier Tubes. VI. Photodiodes As Substitutes For Photomultiplier Tubes. VII. Scintillation Pulse Shape Analysis. VIII. Hybrid Photomultiplier Tubes. IX. Position-Sensing Photomultiplier Tubes. X. Photoionization Detectors. Chapter 10 Radiation Spectroscopy With Scintillators. I. General Considerations In Gamma-Ray Spectroscopy. II. Gamma-Ray Interactions. III. Predicted Response Functions. IV. Properties Of Scintillation Gamma-Ray Spectrometers. V. Response Of Scintillation Detectors To Neutrons. VI. Electron Spectroscopy With Scintillators. VII. Specialized Detector Configurations Based On Scintillation. Chapter 11 Semiconductor Diode Detectors. I. Semiconductor Properties. II. The Action Of Ionizing Radiation In Semiconductors. III. Semiconductors As Radiation Detectors. IV. Semiconductor Detector Configurations. V. Operational Characteristics. VI. Applications Of Silicon Diode Detectors. Chapter 12 Germanium Gamma-Ray Detectors. I. General Considerations. II. Configurations Of Germanium Detectors. III. Germanium Detector Operational Characteristics. IV. Gamma-Ray Spectroscopy With Germanium Detectors. Chapter 13 Other Solid-State Detectors. I. Lithium-Drifted Silicon Detectors. II. Semiconductor Materials Other Than Silicon Or Germanium. III. Avalanche Detectors. IV. Photoconductive Detectors. V. Position-Sensitive Semiconductor Detectors. Chapter 14 Slow Neutron Detection Methods. I. Nuclear Reactions Of Interest In Neutron Detection. II. Detectors Based On The Boron Reaction. III. Detectors Based On Other Conversion Reactions. IV. Reactor Instrumentation. Chapter 15 Fast Neutron Detection And Spectroscopy. I. Counters Based On Neutron Moderation. II. Detectors Based On Fast Neutron-Induced Reactions. III. Detectors That Utilize Fast Neutron Scattering. Chapter 16 Pulse Processing. I. Overview Of Pulse Processing. II. Device Impedances. III. Coaxial Cables. IV. Linear And Logic Pulses. V. Instrument Standards. VI. Summary Of Pulse-Processing Units. VII. Application Specific Integrated Circuits (ASICS). VIII. Components Common To Many Applications. Chapter 17 Pulse Shaping, Counting, And Timing. I. Pulse Shaping. II. Pulse Counting Systems. III. Pulse Height Analysis Systems. IV. Digital Pulse Processing. V. Systems Involving Pulse Timing. VI. Pulse Shape Discrimination. Chapter 18 Multichannel Pulse Analysis. I. Single-Channel Methods. II. General Multichannel Characteristics. III. The Multichannel Analyzer. IV. Spectrum Stabilization And Relocation. V. Spectrum Analysis. Chapter 19 Miscellaneous Detector Types. I. Cherenkov Detectors. II. Gas-Filled Detectors In Self-Quenched Streamer Mode. III. High-Pressure Xenon Spectrometers. IV. Liquid Ionization And Proportional Counters. V. Cryogenic Detectors. VI. Photographic Emulsions. VII. Thermoluminescent Dosimeters And Image Plates. VIII. Track-Etch Detectors. IX. Superheated Drop Or "Bubble Detectors". X. Neutron Detection By Activation. XI. Detection Methods Based On Integrated Circuit Components. Chapter 20 Background And Detector Shielding. I. Sources Of Background. II. Background In Gamma-Ray Spectra. III. Background In Other Detectors. IV. Shielding Materials. V. Active Methods Of Background Reduction. Appendix A The NIM, CAMAC, And VME Instrumentation Standards. Appendix B Derivation Of The Expression For Sample Variance In Chapter 3. Appendix C Statistical Behavior Of Counting Data For Variable Mean Value. Appendix D The Shockley-Ramo Theorem For Induced Charge.
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paper_title: Development of radiation therapy optimization.

paper_content:

The principal radiobiological problems in the treatment of advanced tumors and the solution of many of them by radiobiologically optimized intensity-modulated radiation therapy are presented. Considerable improvements of the treatment outcome using radiobiologically optimized intensity-modulated treatments are achieved by: (a) increasing the tumor dose and dose per fraction; (b) keeping constant or even reducing slightly the dose and dose per fraction to organs at risk, (c) reducing the overall treatment time and the number of treatment fractions. The merits of the new radiation modalities and advanced intensity-modulated treatment techniques are compared in terms of equipment costs per patient cured. It is predicted that the new development of radiobiologically optimized intensity-modulated radiation therapy will rapidly become an important clinical tool, increasing the efficiency of the collaboration between radiation physicists, radiation biologists and radiation oncologists. Not only does it allow the optimal treatment of every patient, but it also promotes an efficient feedback of treatment outcome and complication data to improve the accuracy of known dose response relations to further augment future treatment results. Equipment costs may go up during a transition period until efficient interfaces between new diagnostic equipment, treatment-planning systems and intensity-modulated treatment units are fully developed. From then onwards the cost of high quality biologically optimized intensity-modulated treatments will decrease and so will the treatment time and personnel requirements, at the same time as the treatment quality is greatly improved particularly for more advanced tumors.
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paper_title: From photovoltaics to medical imaging: Applications of thin-film CdTe in x-ray detection

paper_content:

Recent developments in photovoltaics created a commercially viable technology of large area uniform thin-film structures, potentially extendable to the field of medical imaging, where the capability of producing large area x-ray detectors is essential for the successful diagnosis and treatment of cancer. We propose a large area thin-film CdTe structure suitable for radiation detection and discuss its main characteristics under x-ray beams used in radiation therapy. While based on the same principle, the details of its operations are very dissimilar from that of photovoltaics.
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paper_title: Optical imaging as an expansion of nuclear medicine: Cerenkov-based luminescence vs fluorescence-based luminescence

paper_content:

Integration of optical imaging technologies can further strengthen the field of radioguided surgery. Rather than using two separate chemical entities to achieve this extension, hybrid imaging agents can be used that contain both radionuclear and optical properties. Two types of such hybrid imaging agents are available: (1) hybrid imaging agents generated by Cerenkov luminescence imaging (CLI) of β-emitters and (2) hybrid imaging agents that contain both a radioactive moiety and a fluorescent dye. One major challenge clinicians are now facing is to determine the potential value of these approaches. With this tutorial review we intend to clarify the differences between the two approaches and highlight the clinical potential of hybrid imaging during image-guided surgery applications.
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paper_title: RADFET: A review of the use of metal-oxide-silicon devices as integrating dosimeters

paper_content:

Abstract Calibrated, radiation-sensitive metal-oxide-silicon field-effect transistors (RADFETs) have been launched into space and used in the laboratory to measure the doses from a variety of radiation sources. These experiments have demonstrated that the RADFET provides a convenient method for the continuous monitoring of total dose. The electrical output consists of a d.c. voltage which can be converted electronically to a value for accumulated dose. The voltage can be read remotely and displayed continuously. This review briefly outlines the physical mechanisms by which radiation dose is registered by RADFETs, describes the characteristics and performance of a practical RADFET and discusses applications. In addition to the name “RADFET”, these devices have been called “MOS Dosimeters”, “Mosimeters” and “Space Charge (SC) Transducers”.
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paper_title: Application of a natural diamond detector for the measurement of relative dose distributions in radiotherapy

paper_content:

The suitability of a natural diamond detector with a special contact system for the measurement or relative dose distributions in selected radiotherapy applications was studied. The performance of the diamond detector was analysed by comparison with measurements using an ionization chamber and a silicon diode detector. The good stability, high response and good spatial resolution of the diamond detector were demonstrated by relative measurements in high energy photon and electron beams and around the 137Cs source of an afterloading device. The application of the diamond detectors for relative as well as absolute dose measurements of beta ray ophthalmic applicators was also highlighted. It is concluded that the diamond with the special contact system is a suitable detector for relative dose measurements in a wide variety of applications, especially when high response and high spatial resolution is required.
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paper_title: Displacement Damage Effects in Irradiated Semiconductor Devices

paper_content:

A review of radiation-induced displacement damage effects in semiconductor devices is presented, with emphasis placed on silicon technology. The history of displacement damage studies is summarized, and damage production mechanisms are discussed. Properties of defect clusters and isolated defects are addressed. Displacement damage effects in materials and devices are considered, including effects produced in silicon particle detectors, visible imaging arrays, and solar cells. Additional topics examined include NIEL scaling, carrier concentration changes, random telegraph signals, radiation hardness assurance, and simulation methods for displacement damage. Areas needing further study are noted.
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paper_title: Application of p-Channel Power VDMOSFET as a High Radiation Doses Sensor

paper_content:

This paper presents a comparative study of RADFETs and commercial p-channel power VDMOSFETs sensitivity to gamma-ray irradiation. Sensitivity was characterized by the threshold voltage shift determined from extrapolated linear region of transfer characteristics in saturation as a function of radiation dose. Sensitivity was followed in the dose range from 100 Gy to 500 Gy without and with $ + 10~\hbox{V}$ gate bias. Linear dependence between threshold voltage shift and radiation dose was established for components for which the gate bias during irradiation was $ + 10~\hbox{V}$ . Sensitivity of p-channel power VDMOSFETs is larger than the RADFETs, and it is a consequence of a larger concentration of fixed traps generated by gamma-ray irradiation. The mechanisms responsible for the threshold voltage shift during irradiation have been discussed as well. The fading of these components was also monitored at room temperature up to 24 hours and it was shown that it is larger in p-channel power VDMOSFETs then in RADFETs.
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paper_title: Using RADFET for the real-time measurement of gamma radiation dose rate

paper_content:

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20 and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65 to 32.1 Gy h−1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose.
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paper_title: Current mode response of phototransistors to gamma radiation

paper_content:

Abstract This paper investigates the current mode response of four commercial NPN phototransistors under gamma radiation exposure from Co-60 source, with the aim to evaluate their applicability for gamma radiation dosimetry. The radiation-induced collector current was measured while the phototransistors were successively biased with 10 V and 20 V between collector and emitter. The main aspects analyzed in the experiment were the stability of the induced current, dependence of the induced current with respect to dose rate, short-term repeatability of the induced current and relation between the induced charge and the absorbed dose. The current response of all samples was stable during the 2-min irradiation sessions at the dose rates from 0.65 Gy/h to 32.1 Gy/h, with the relative uncertainty less than 5% in all cases, and the variation of the mean effective current as a function of dose rate was well fitted with the standard power relation. During the three consecutive 2-min irradiation sessions at the dose rate of 32.1 Gy/h, the repeatability of the induced charge was very good for all samples with the relative uncertainty below 3%. However, for continuous irradiation up to the absorbed dose of 20 Gy (10-min irradiation at the dose rate of 60 Gy/h), all samples exhibited significant current fall which can be attributed to the radiation-induced current gain degradation. As a result of the current degradation, the relationship between the induced charge and the absorbed dose was non-linear and it was demonstrated that the second order polynomial can be used as a calibration equation for determination of absorbed dose. The obtained results have shown that only one of the examined phototransistors may be a suitable candidate for gamma radiation dosimetry employing Co-60 source, since it has exhibited the highest current sensitivity, best linearity of the induced current with respect to dose rate and smallest dose rate dependence of the charge sensitivity.
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paper_title: Photoconductive gain modelling of GaN photodetectors

paper_content:

A model to explain the behaviour of GaN photoconductive detectors is proposed, and it is based on the idea of a volume modulation rather than a carrier density modulation. Space charge regions inside the semiconductor produce a variation of the conductive volume when carriers are photogenerated. The strong non-exponential photocurrent decays result from carrier capture processes over the barriers associated with space charge regions. By means of computer simulation, this model explains quite well the behaviour of current GaN photoconductor devices and predicts their time response, temperature dependence and responsivity properties.
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paper_title: Solar Cells: In Research and Applications—A Review

paper_content:

The light from the Sun is a non-vanishing renewable source of energy which is free from environmental pollution and noise. It can easily compensate the energy drawn from the non-renewable sources of energy such as fossil fuels and petroleum deposits inside the earth. The fabrication of solar cells has passed through a large number of improvement steps from one generation to another. Silicon based solar cells were the first generation solar cells grown on Si wafers, mainly single crystals. Further development to thin films, dye sensitized solar cells and organic solar cells enhanced the cell efficiency. The development is basically hindered by the cost and efficiency. In order to choose the right solar cell for a specific geographic location, we are required to understand fundamental mechanisms and functions of several solar technologies that are widely studied. In this article, we have reviewed a progressive development in the solar cell research from one generation to other, and discussed about their future trends and aspects. The article also tries to emphasize the various practices and methods to promote the benefits of solar energy.
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paper_title: Development and evaluation of gallium nitride-based thin films for x-ray dosimetry.

paper_content:

X-ray radiation plays an important role in medical procedures ranging from diagnostics to therapeutics. Due to the harm such ionizing radiation can cause, it has become common practice to closely monitor the dosages received by patients. To this end, precise online dosimeters have been developed with the dual objectives of monitoring radiation in the region of interest and improving therapeutic methods. In this work, we evaluate GaN thin film high electron mobility heterostructures with sub-mm(2) detection areas as x-ray radiation detectors. Devices were tested using 40-300 kV Bremsstrahlung x-ray sources. We find that the photoconductive device response exhibits a large gain, is almost independent of the angle of irradiation, and is constant to within 2% of the signal throughout this medical diagnostic x-ray range, indicating that these sensors do not require recalibration for geometry or energy. Furthermore, the devices show a high sensitivity to x-ray intensity and can measure in the air kerma rate (free-in-air) range of 1 µGy s(-1) to 10 mGy s(-1) with a signal stability of ±1% and a linear total dose response over time. Medical conditions were simulated by measurements of device responses to irradiation through human torso phantoms. Direct x-ray imaging is demonstrated using the index finger and wrist sections of a human phantom. The results presented here indicate that GaN-based thin film devices exhibit a wide range of properties, which make them promising candidates for dosimetry applications. In addition, with potential detection volumes smaller than 10(-6) cm(3), they are well suited for high-resolution x-ray imaging. Moreover, with additional engineering steps, these devices can be adapted to potentially provide both in vivo biosensing and x-ray dosimetry.
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paper_title: Recent advances in compound semiconductor radiation detectors

paper_content:

Abstract Recent developments in compound semiconductor detectors are reviewed, highlighting the latest spectroscopic performance from devices fabricated from a range of wide bandgap materials. Cadmium zinc telluride and cadmium telluride continue to dominate the field, with a range of prototype imaging detectors under development, principally for nuclear medicine and X-ray astronomy applications. Improvements in material quality and supply plus metal–semiconductor contact technologies are discussed, as is the continued development of single polarity charge sensing electrode structures. Other material systems are also reviewed, covering the latest results from intermediate- Z materials such as gallium arsenide and indium phosphide, and high- Z materials including mercuric iodide and thallium bromide. The technological challenges of these materials are summarised and the prospects for future imaging array detectors highlighted.
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paper_title: Precise dose evaluation using a commercial phototransistor as a radiation detector

paper_content:

An experimental arrangement and a circuitry based on an NPN phototransistor-type silicon radiation detector have been used for evaluating the X-ray beam dose in the diagnostic range. The circuitry was built to allow alteration of the electric field in the phototransistor internal structure, with some devices that have an available base connection. By changing the transistor base bias it is possible to alter its operation point to obtain a response gain from the selected photon energy range. In this way we have made an electronic energy-domain discretisation and we are investigating a model to calculate the dose contribution from each energy discretised into 10 keV steps. The method has been tested in filtered radiation beams generated from an HF-160 Pantak X-ray unit and compared with the usual dosimetry method. Our results have demonstrated that it is possible to make such a dose deconvolution from 40 to 140 keV energies by controlling the phototransistor base bias properly.
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paper_title: Optical imaging of Cerenkov light generation from positron-emitting radiotracers.

paper_content:

Radiotracers labeled with high-energy positron emitters, such as those commonly used for positron emission tomography studies, emit visible light immediately following decay in a medium. This phenomenon, not previously described for these imaging tracers, is consistent with Cerenkov radiation and has several potential applications, especially for in vivo molecular imaging studies. Herein we detail a new molecular imaging tool, Cerenkov Luminescence Imaging, the experiments conducted that support our interpretation of the source of the signal, and proof-of-concept in vivo studies that set the foundation for future application of this new method.
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paper_title: Dosimetry of ionising radiation in modern radiation oncology

paper_content:

Dosimetry of ionising radiation is a well-established and mature branch of physical sciences with many applications in medicine and biology. In particular radiotherapy relies on dosimetry for optimisation of cancer treatment and avoidance of severe toxicity for patients. Several novel developments in radiotherapy have introduced new challenges for dosimetry with small and dynamically changing radiation fields being central to many of these applications such as stereotactic ablative body radiotherapy and intensity modulated radiation therapy. There is also an increasing awareness of low doses given to structures not in the target region and the associated risk of secondary cancer induction. Here accurate dosimetry is important not only for treatment optimisation but also for the generation of data that can inform radiation protection approaches in the future. The article introduces some of the challenges and highlights the interdependence of dosimetric calculations and measurements. Dosimetric concepts are explored in the context of six application fields: reference dosimetry, small fields, low dose out of field, in vivo dosimetry, brachytherapy and auditing of radiotherapy practice. Recent developments of dosimeters that can be used for these purposes are discussed using spatial resolution and number of dimensions for measurement as sorting criteria. While dosimetry is ever evolving to address the needs of advancing applications of radiation in medicine two fundamental issues remain: the accuracy of the measurement from a scientific perspective and the importance to link the measurement to a clinically relevant question. This review aims to provide an update on both of these.
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paper_title: Photons across medicine: relating optical and nuclear imaging.

paper_content:

The Optics in the Life Sciences conference sponsored by the Optical Society of America was held in Waikoloa Beach, HI on April 14 – 18, 2013. Papers were presented in the areas of Bio-Optics: Design & Application, Novel Techniques in Microscopy, Optical Molecular Probes, Imaging & Drug Delivery, and Optical Trapping Applications. A focal point of the meeting was a special symposium entitled “Photons Across Medicine”, organized by Adam Wax, Duke University, highlighting activities of joint interest between the Optical Society of America (OSA) and the Society for Nuclear Medicine and Molecular Imaging (SNMMI). This paper is a synopsis of the presentations made at this joint symposium. Central to the special symposium presentations was the fact that the optical and nuclear imaging communities share common interests and challenges. These are highlighted in this article. Also discussed was the fact that the nuclear technologies in imaging have found their way into general clinical utility, a feat that has yet to be achieved by optical methods. Because of the common ground shared by the two technologies, coordination between the two societies should be planned.
---
paper_title: Review of biomedical Čerenkov luminescence imaging applications

paper_content:

Cerenkov radiation is a fascinating optical signal, which has been exploited for unique diagnostic biological sensing and imaging, with significantly expanded use just in the last half decade. Cerenkov Luminescence Imaging (CLI) has desirable capabilities for niche applications, using specially designed measurement systems that report on radiation distributions, radiotracer and nanoparticle concentrations, and are directly applied to procedures such as medicine assessment, endoscopy, surgery, quality assurance and dosimetry. When compared to the other imaging tools such as PET and SPECT, CLI can have the key advantage of lower cost, higher throughput and lower imaging time. CLI can also provide imaging and dosimetry information from both radioisotopes and linear accelerator irradiation. The relatively short range of optical photon transport in tissue means that direct Cerenkov luminescence imaging is restricted to small animals or near surface human use. Use of Cerenkov-excitation for additional molecular probes, is now emerging as a key tool for biosensing or radiosensitization. This review evaluates these new improvements in CLI for both medical value and biological insight.
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paper_title: Čerenkov radiation, and its applications

paper_content:

The paper opens with a brief review of the original discovery of the radiation and the physical principles of the process that gives rise to it. This is followed by an elementary account of the theory of the effect. A general survey of the practical applications to cosmic-ray and high-energy physics is then presented, with two examples of modern detectors discussed in greater detail. The article concludes with an account of recent experiments carried out on light pulses from the night-sky associated with cosmic-ray showers, found to be due to Cerenkov radiation in the atmosphere.
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paper_title: Radiation hardness studies of CdTe thin films for clinical high-energy photon beam detectors

paper_content:

In radiation oncology applications, the need for higher-quality images has been driven by recent advances in radiation delivery systems that require online imaging. The existing electronic imaging devices commonly used to acquire portal images implement amorphous silicon (a-Si) detector, which exhibits poor image quality. Efforts for improvement have mostly been in the areas of noise and scatter reduction through software. This has not been successful due to inherent shortcomings of a-Si material. Cadmium telluride (CdTe) semiconductor has long been recognized as highly suitable for use in X-ray detectors in both spectroscopic and imaging applications. Development of such systems has mostly concentrated on single crystal CdTe. Recent advances in thin-film deposition technology suggest replacement of crystalline material with its polycrystalline counterpart, offering ease of large-area device fabrication and achievement of higher resolution as well as a favorable cost difference. While bulk CdTe material was found to have superior radiation hardness, thin films have not been evaluated from that prospective, in particular under high-energy photon beam typical of radiation treatment applications. We assess the performance of thin-film CdTe devices utilizing 6 MeV photon beam and find no consistent trend for material degradation under doses far exceeding the typical radiation therapy detector lifetime dose.
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paper_title: Optically stimulated luminescence (OSL) dosimetry in medicine

paper_content:

This paper reviews fundamental and practical aspects of optically stimulated luminescence (OSL) dosimetry pertaining to applications in medicine, having particularly in mind new researchers and medical physicists interested in gaining familiarity with the field. A basic phenomenological model for OSL is presented and the key processes affecting the outcome of an OSL measurement are discussed. Practical aspects discussed include stimulation modalities (continuous-wave OSL, pulsed OSL and linear modulation OSL), basic experimental setup, available OSL readers, optical fiber systems and basic properties of available OSL dosimeters. Finally, results from the recent literature on applications of OSL in radiotherapy, radiodiagnostics and heavy charged particle dosimetry are discussed in light of the theoretical and practical framework presented in this review. Open questions and future challenges in OSL dosimetry are highlighted as a guide to the research needed to further advance the field.
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paper_title: Silicon solar cells as a gamma ray dosimeter

paper_content:

Abstract Monocrystalline silicon solar cell of the construction n + pp ++ Passivated Emitter Solar Cell (PESC) irradiated by 60 Co gamma ray dose was studied. Thermoluminescence detectors (TLD) main dosimetry peak was investigated. The results showed that it is possible to determine gamma dose more accurate from TL main dosimetry peak for monocrystalline silicon solar cell in comparison with TLD (100). Also the various sources of uncertainty were analyzed. The expanded uncertainty at 95% confidence level should be added to the value of measurements to obtain accurate dose.
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paper_title: Comparative Study of Gamma and Neutron Irradiation Effects on the Silicon Solar Cells Parameters

paper_content:

Due to its wide application areas, solar cells are exposed, in their work environment, to different types of radiation (cosmic radiation in the upper layers of the atmosphere, military and civilian nuclear facilities). Moreover, the used nuclear fuel emits y photons and neutrons at the same time, so different types of radiation damage appeared in solar cells located in the vicinity of these fuels. These damage have been caused by both gamma and neutron radiation. That's why very extensive researches have been undertaken with the aim of developing semiconductor devices whose work will be reliable in terms of increased levels of radiation. From the technological point of view, it is important to determine changes, caused by radiation, in the parameters of the silicon solar cells that affect their work. The aim of this paper is to present the comparative study of gamma and neutron irradiation effects on the solar cells parameters.
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paper_title: Real-time Cherenkov emission portal imaging during CyberKnife®radiotherapy

paper_content:

The feasibility of real-time portal imaging during radiation therapy, through the Cherenkov emission (CE) effect is investigated via a medical linear accelerator (CyberKnife®) irradiating a partially-filled water tank with a 60 mm circular beam. A graticule of lead/plywood and a number of tissue equivalent materials were alternatively placed at the beam entrance face while the induced CE at the exit face was imaged using a gated electron-multiplying-intensified-charged-coupled device (emICCD) for both stationary and dynamic scenarios. This was replicated on an Elekta Synergy® linear accelerator with portal images acquired using the iViewGT™ system. Profiles across the acquired portal images were analysed to reveal the potential resolution and contrast limits of this novel CE based portal imaging technique and compared against the current standard. The CE resolution study revealed that using the lead/plywood graticule, separations down to 3.4 ± 0.5 mm can be resolved. A 28 mm thick tissue-equivalent rod with electron density of 1.69 relative to water demonstrated a CE contrast of 15% through air and 14% through water sections, as compared to a corresponding contrast of 19% and 12% using the iViewGT™ system. For dynamic scenarios, video rate imaging with 30 frames per second was achieved. It is demonstrated that CE-based portal imaging is feasible to identify both stationary and dynamic objects within a CyberKnife® radiotherapy treatment field.
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paper_title: PiN photodiode performance comparison for dosimetry in radiology applications.

paper_content:

Performance comparison of selected photodiodes for usage as radiation detectors for radio-protection is presented. In this study, based on the criteria of minimum sensitive area of 5mm2, minimum half angle 60° and low cost, four commercial photodiodes are selected for evaluation: SFH205, SFH206, BPW34, and BPX90F. Photodiodes are low cost, small volume and lightweight detectors. As an electronic transducer, photodiode detector is an attractive approach for the development of low power portable electronic dosimeter for direct-reading real-time radiation dose measurement. The devices have been studied with respect to sensitivity (efficiency) in X-rays and gamma rays detection, repeatability and linearity in air kerma.
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paper_title: Radiotherapy-induced Cherenkov luminescence imaging in a human body phantom.

paper_content:

Radiation therapy produces Cherenkov optical emission in tissue, and this light can be utilized to activate molecular probes. The feasibility of sensing luminescence from a tissue molecular oxygen sensor from within a human body phantom was examined using the geometry of the axillary lymph node region. Detection of regions down to 30-mm deep was feasible with submillimeter spatial resolution with the total quantity of the phosphorescent sensor PtG4 near 1 nanomole. Radiation sheet scanning in an epi-illumination geometry provided optimal coverage, and maximum intensity projection images provided illustration of the concept. This work provides the preliminary information needed to attempt this type of imaging in vivo.
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paper_title: An alternative method for using bipolar junction transistors as a radiation dosimetry detector in breast cancer treatment

paper_content:

Abstract Silicon photodetectors and MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) are frequently used devices for measuring ionizing radiation in health physics instrumentation. The Bipolar Junction Transistor (BJT) is not a typical device used as a detector for measuring some physical quantities in radiotherapy beams due to its loss of sensitivity to ionizing radiation, as a consequence of radiation damage in the silicon semiconductor substrate. Actually, the know-how of the BJT characteristic curves and its response to ionizing radiation leads us to suggest an alternative method to estimate the radiation dose value in breast cancer treatments. The BJT parameter to be evaluated before and after the irradiation procedure is the BJT amplification factor, also called DC gain β . In this work, the study was done using a BJT known as Darlington type, within an Alderson Rando anthropomorphic phantom. Darlington transistors have very high gain and this feature allowed that the BJT gain changes to be correlated with the dose of the radiation beam. The results indicate that this new method could be an alternative option to estimate the dose value in the phantom for measurements in breast cancer radiotherapy.
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paper_title: Radiation therapy dosimetry system.

paper_content:

New therapeutic treatments generally aim to increase therapeutic efficacy while minimizing toxicity. Many aspects of radiation dosimetry have been studied and developed particularly in the field of external radiation. The success of radiotherapy relies on monitoring the dose of radiation to which the tumor and the adjacent tissues are exposed. Radiotherapy techniques have evolved through a rapid transition from conventional three-dimensional (3D) conformal radiation therapy to intensity-modulated radiation therapy (IMRT) treatments or radiosurgery and robotic radiation therapy. These advances push the frontiers in our effort to provide better patient care by improving the precision of the absorbed dose delivered. This paper presents state-of-the art radiation therapy dosimetry techniques as well as the value of integral dosimetry (INDOS), which shows promise in the fulfillment of radiation therapy dosimetry requirements.
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paper_title: A prototype scintillation dosimeter customized for small and dynamic megavoltage radiation fields

paper_content:

A prototype plastic scintillation dosimeter has been developed with a small sensitive volume, rapid response and good dosimetric performance. The novelty of this design is the use of an air core light guide to transport the scintillation signal out of the primary radiation field. The significance of this innovation is that it eliminates the Cerenkov background signal that is generated in conventional optical fibres. The dosimeter performance was compared to existing commercial dosimeters in 6 MV and 18 MV photon beams and 6 MeV and 20 MeV electron beams, in both static and dynamic fields. The dosimeter was tested in small static fields and in dynamically delivered fields where the detector volume is shielded, while the stem is irradiated. The depth dose measurements for the photon beams agreed with ionization chamber measurements to within 1.6%, except in the build-up region due to positional uncertainty. For the 6 MeV and 20 MeV electron beams, the percentage depth dose measurements agreed with the ionization chamber measurements to within 3.6% and 4.5%, respectively. For field sizes of 1 cm × 1 cm and greater, the air core dosimeter readings agreed with diamond detector readings to within 1.2%. The air core dosimeter was accurate in dynamically delivered fields and had no measurable stem effect. The air core dosimeter was accurate over a range of field sizes, energies and dose rates, confirming that it is a sensitive and accurate dosimeter with high spatial resolution suitable for use in megavoltage photon and electron beams.
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paper_title: LEDs for lighting: Basic physics and prospects for energy savings

paper_content:

Abstract In 2014, Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura received the Nobel Prize in Physics for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”. Indeed, in the recent years, Light-Emitting Diodes (LEDs) have progressively made their way to the home lighting market, as well as to other mass markets. This article aims at giving an insight on LEDs physics, on the key inventions that led to the 2014 Nobel Prize and on the prospects for energy savings that LEDs could allow.
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paper_title: MOSFET Models for VLSI Circuit Simulation: Theory and Practice

paper_content:

This study discusses MOS transistor models and their parameters required for VLSI simulation of MOS-integrated circuits. It gives detailed presentation of model parameter determination for MOS models. Various models are developed ranging from simple to more sophisticated models that take into account new physical effects observed in submicron devices used in today's MOS VLSI technology. The assumptions used to arrive at the models are emphasized so that the accuracy of the model in describing the device characteristics are clearly understood. Understanding these models is essential when designing circuits for the state-of-the-art MOS ICs. Since threshold voltage is the single-most important MOSFET parameter, a full chapter is devoted to the development of the device threshold voltage model. Due to the importance of designing reliable circuits, the device reliability models, as applied for circuit simulations, are also covered. Since the device parameters vary due to inherent processing variations, how to arrive at worst-case design parameters are also covered. Presentation of the material is such that even an undergraduate student, not well familiar with semiconductor device physics, can understand the intricacies of MOSFET modeling. The book serves as a technical source in the area of MOSFET modeling for state-of-the-art MOSFET technology for both practicing device and circuit engineers, and engineering students interested in the area.
---
paper_title: Comparative Study of Gamma and Neutron Irradiation Effects on the Silicon Solar Cells Parameters

paper_content:

Due to its wide application areas, solar cells are exposed, in their work environment, to different types of radiation (cosmic radiation in the upper layers of the atmosphere, military and civilian nuclear facilities). Moreover, the used nuclear fuel emits y photons and neutrons at the same time, so different types of radiation damage appeared in solar cells located in the vicinity of these fuels. These damage have been caused by both gamma and neutron radiation. That's why very extensive researches have been undertaken with the aim of developing semiconductor devices whose work will be reliable in terms of increased levels of radiation. From the technological point of view, it is important to determine changes, caused by radiation, in the parameters of the silicon solar cells that affect their work. The aim of this paper is to present the comparative study of gamma and neutron irradiation effects on the solar cells parameters.
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paper_title: The Development of Fluorescence Imaging Systems for Clinical Applications - Part I, Broad-Field Fluorescence Imaging

paper_content:

This article proposed a novel classification on fluorescence imaging for clinical applications, and presented a camera-based instrument to verify the functions by an animal mode. The imaging technologies of fluorescence currently are developed in biological medicine included broad-field fluorescence imaging, point-probe fluorescence imaging, and cross-sectional endoluminal fluorescence imaging respectively. This periodical's editor introduced broad-field fluorescence imaging's latest developments in technology in this issue, and illustrated a photo retouching system for decreasing the fluorescence signal-to-noise ratio in photodynamic therapy (PDT) for skin cancer. The animal test also verified that this camera-based instrument still could capture the red fluorescence under a low-dosed light sensitive drug and the scope of distribution of melanoma cells in the vein could clearly be observed.
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paper_title: Solar Cells: In Research and Applications—A Review

paper_content:

The light from the Sun is a non-vanishing renewable source of energy which is free from environmental pollution and noise. It can easily compensate the energy drawn from the non-renewable sources of energy such as fossil fuels and petroleum deposits inside the earth. The fabrication of solar cells has passed through a large number of improvement steps from one generation to another. Silicon based solar cells were the first generation solar cells grown on Si wafers, mainly single crystals. Further development to thin films, dye sensitized solar cells and organic solar cells enhanced the cell efficiency. The development is basically hindered by the cost and efficiency. In order to choose the right solar cell for a specific geographic location, we are required to understand fundamental mechanisms and functions of several solar technologies that are widely studied. In this article, we have reviewed a progressive development in the solar cell research from one generation to other, and discussed about their future trends and aspects. The article also tries to emphasize the various practices and methods to promote the benefits of solar energy.
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paper_title: Development and evaluation of gallium nitride-based thin films for x-ray dosimetry.

paper_content:

X-ray radiation plays an important role in medical procedures ranging from diagnostics to therapeutics. Due to the harm such ionizing radiation can cause, it has become common practice to closely monitor the dosages received by patients. To this end, precise online dosimeters have been developed with the dual objectives of monitoring radiation in the region of interest and improving therapeutic methods. In this work, we evaluate GaN thin film high electron mobility heterostructures with sub-mm(2) detection areas as x-ray radiation detectors. Devices were tested using 40-300 kV Bremsstrahlung x-ray sources. We find that the photoconductive device response exhibits a large gain, is almost independent of the angle of irradiation, and is constant to within 2% of the signal throughout this medical diagnostic x-ray range, indicating that these sensors do not require recalibration for geometry or energy. Furthermore, the devices show a high sensitivity to x-ray intensity and can measure in the air kerma rate (free-in-air) range of 1 µGy s(-1) to 10 mGy s(-1) with a signal stability of ±1% and a linear total dose response over time. Medical conditions were simulated by measurements of device responses to irradiation through human torso phantoms. Direct x-ray imaging is demonstrated using the index finger and wrist sections of a human phantom. The results presented here indicate that GaN-based thin film devices exhibit a wide range of properties, which make them promising candidates for dosimetry applications. In addition, with potential detection volumes smaller than 10(-6) cm(3), they are well suited for high-resolution x-ray imaging. Moreover, with additional engineering steps, these devices can be adapted to potentially provide both in vivo biosensing and x-ray dosimetry.
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paper_title: CCD or CMOS camera noise characterisation

paper_content:

To achieve optimum imaging performance, any camera system has to be thoroughly checked before being used, particular care being given in evaluating the different contributions due to noise. Our work presents a method for characterising the different sources of noise affecting CCD or CMOS cameras, emphasising the too often overlooked pattern noise. This method is an extended and theoretical approach of the well-known photon transfer technique [1]. Experimentation on our high speed CCD imager illustrates this approach.
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paper_title: CCD or CMOS Image sensor for photography

paper_content:

An Image sensor is converts an image into a digital signal. Both CCD (charged coupled device) and CMOS (complementary metal oxide semiconductor) image sensor technologies are essential for image capturing. CMOS image sensor is still in their early years, still it's set to develop but CCD has number of advantages over CMOS. CCD will give you a assurance for more compact, high image quality and potentially more efficient camera. Both CCD and CMOS Technologies have explained in this paper and also how images are captured as well as types for both types of image sensors have been descried. Some issues such as performance characteristics for better image quality for photography have been covered.
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paper_title: Current mode response of phototransistors to gamma radiation

paper_content:

Abstract This paper investigates the current mode response of four commercial NPN phototransistors under gamma radiation exposure from Co-60 source, with the aim to evaluate their applicability for gamma radiation dosimetry. The radiation-induced collector current was measured while the phototransistors were successively biased with 10 V and 20 V between collector and emitter. The main aspects analyzed in the experiment were the stability of the induced current, dependence of the induced current with respect to dose rate, short-term repeatability of the induced current and relation between the induced charge and the absorbed dose. The current response of all samples was stable during the 2-min irradiation sessions at the dose rates from 0.65 Gy/h to 32.1 Gy/h, with the relative uncertainty less than 5% in all cases, and the variation of the mean effective current as a function of dose rate was well fitted with the standard power relation. During the three consecutive 2-min irradiation sessions at the dose rate of 32.1 Gy/h, the repeatability of the induced charge was very good for all samples with the relative uncertainty below 3%. However, for continuous irradiation up to the absorbed dose of 20 Gy (10-min irradiation at the dose rate of 60 Gy/h), all samples exhibited significant current fall which can be attributed to the radiation-induced current gain degradation. As a result of the current degradation, the relationship between the induced charge and the absorbed dose was non-linear and it was demonstrated that the second order polynomial can be used as a calibration equation for determination of absorbed dose. The obtained results have shown that only one of the examined phototransistors may be a suitable candidate for gamma radiation dosimetry employing Co-60 source, since it has exhibited the highest current sensitivity, best linearity of the induced current with respect to dose rate and smallest dose rate dependence of the charge sensitivity.
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paper_title: Stereotactic body radiotherapy for primary hepatocellular carcinoma.

paper_content:

PURPOSE ::: To evaluate the safety and efficacy of stereotactic body radiotherapy (SBRT) for the treatment of primary hepatocellular carcinoma (HCC). ::: ::: ::: METHODS AND MATERIALS ::: From 2005 to 2009, 60 patients with liver-confined HCC were treated with SBRT at the Indiana University Simon Cancer Center: 36 Child-Turcotte-Pugh (CTP) Class A and 24 CTP Class B. The median number of fractions, dose per fraction, and total dose, was 3, 14 Gy, and 44 Gy, respectively, for those with CTP Class A cirrhosis and 5, 8 Gy, and 40 Gy, respectively, for those with CTP Class B. Treatment was delivered via 6 to 12 beams and in nearly all cases was prescribed to the 80% isodose line. The records of all patients were reviewed, and treatment response was scored according to Response Evaluation Criteria in Solid Tumors v1.1. Toxicity was graded according to the Common Terminology Criteria for Adverse Events v4.0. Local control (LC), time to progression (TTP), progression-free survival (PFS), and overall survival (OS) were calculated according to the method of Kaplan and Meier. ::: ::: ::: RESULTS ::: The median follow-up time was 27 months, and the median tumor diameter was 3.2 cm. The 2-year LC, PFS, and OS were 90%, 48%, and 67%, respectively, with median TTP of 47.8 months. Subsequently, 23 patients underwent transplant, with a median time to transplant of 7 months. There were no ≥Grade 3 nonhematologic toxicities. Thirteen percent of patients experienced an increase in hematologic/hepatic dysfunction greater than 1 grade, and 20% experienced progression in CTP class within 3 months of treatment. ::: ::: ::: CONCLUSIONS ::: SBRT is a safe, effective, noninvasive option for patients with HCC ≤6 cm. As such, SBRT should be considered when bridging to transplant or as definitive therapy for those ineligible for transplant.
---
paper_title: Development and evaluation of gallium nitride-based thin films for x-ray dosimetry.

paper_content:

X-ray radiation plays an important role in medical procedures ranging from diagnostics to therapeutics. Due to the harm such ionizing radiation can cause, it has become common practice to closely monitor the dosages received by patients. To this end, precise online dosimeters have been developed with the dual objectives of monitoring radiation in the region of interest and improving therapeutic methods. In this work, we evaluate GaN thin film high electron mobility heterostructures with sub-mm(2) detection areas as x-ray radiation detectors. Devices were tested using 40-300 kV Bremsstrahlung x-ray sources. We find that the photoconductive device response exhibits a large gain, is almost independent of the angle of irradiation, and is constant to within 2% of the signal throughout this medical diagnostic x-ray range, indicating that these sensors do not require recalibration for geometry or energy. Furthermore, the devices show a high sensitivity to x-ray intensity and can measure in the air kerma rate (free-in-air) range of 1 µGy s(-1) to 10 mGy s(-1) with a signal stability of ±1% and a linear total dose response over time. Medical conditions were simulated by measurements of device responses to irradiation through human torso phantoms. Direct x-ray imaging is demonstrated using the index finger and wrist sections of a human phantom. The results presented here indicate that GaN-based thin film devices exhibit a wide range of properties, which make them promising candidates for dosimetry applications. In addition, with potential detection volumes smaller than 10(-6) cm(3), they are well suited for high-resolution x-ray imaging. Moreover, with additional engineering steps, these devices can be adapted to potentially provide both in vivo biosensing and x-ray dosimetry.
---
paper_title: Optical imaging of Cerenkov light generation from positron-emitting radiotracers.

paper_content:

Radiotracers labeled with high-energy positron emitters, such as those commonly used for positron emission tomography studies, emit visible light immediately following decay in a medium. This phenomenon, not previously described for these imaging tracers, is consistent with Cerenkov radiation and has several potential applications, especially for in vivo molecular imaging studies. Herein we detail a new molecular imaging tool, Cerenkov Luminescence Imaging, the experiments conducted that support our interpretation of the source of the signal, and proof-of-concept in vivo studies that set the foundation for future application of this new method.
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paper_title: Spine radiosurgery: a dosimetric analysis in 124 patients who received 18 Gy.

paper_content:

PURPOSE ::: To define the safely tolerated doses to organs at risk (OARs) adjacent to the target volume (TV) of spine radiosurgery (SRS) with 18-Gy in a single fraction. ::: ::: ::: METHODS AND MATERIALS ::: A total of 124 patient cases with 165 spine metastases were reviewed. An 18-Gy single-fraction regimen was prescribed to the 90% isodose line encompassing the TV. A constraint of 10 Gy to 10% of the spinal cord outlined 6 mm above and below the TV was used. Dosimetric data to OARs were analyzed. ::: ::: ::: RESULTS ::: A total of 124 patients (100%) were followed-up, and median follow-up time was 7 months (1-50 months). Symptoms and local control were achieved in 114 patients (92%). Acute Radiation Therapy Oncology Group (RTOG) grade 1 oral mucositis occurred in 11 of 11 (100%) patients at risk for oropharyngeal toxicity after cervical spine treatment. There were no RTOG grade 2-4 acute or late complications. Median TV was 43.2 cc (5.3-175.4 cc) and 90% of the TV received median dose of 19 Gy (17-19.8 Gy). Median (range) of spinal cord maximum dose (Dmax), dose to spinal cord 0.35 cc (Dsc0.35), and cord volume receiving 10 Gy (Vsc10) were 13.8 Gy (5.4-21 Gy), 8.9 Gy (2.6-11.4 Gy) and 0.33 cc (0-1.6 cc), respectively. Other OARs were evaluated when in proximity to the TV. Esophagus (n=58), trachea (n=28), oropharynx (n=11), and kidneys (n=34) received median (range) V10 and V15 of 3.1 cc (0-5.8 cc) and 1.2 cc (0-2.9 cc), 2.8 cc (0-4.9 cc), and 0.8 cc (0-2.1 cc), 3.4 cc (0-6.2 cc) and 1.6 cc (0-3.2 cc), 0.3 cc (0-0.8 cc) and 0.08 cc (0-0.1 cc), respectively. ::: ::: ::: CONCLUSIONS ::: Cord Dmax of 14 Gy and D0.35 of 10 Gy are safe dose constraints for 18-Gy single-fraction SRS. Esophagus V10 of 3 cc and V15 of 1 cc, trachea V10 of 3 cc, and V15 of 1 cc, oropharynx V10 of 3.5 cc and V15 of 1.5 cc, kidney V10 of 0.3 cc, and V15 of 0.1 cc are planning guidelines when these OARs are in proximity to the TV.
---
paper_title: Photons across medicine: relating optical and nuclear imaging.

paper_content:

The Optics in the Life Sciences conference sponsored by the Optical Society of America was held in Waikoloa Beach, HI on April 14 – 18, 2013. Papers were presented in the areas of Bio-Optics: Design & Application, Novel Techniques in Microscopy, Optical Molecular Probes, Imaging & Drug Delivery, and Optical Trapping Applications. A focal point of the meeting was a special symposium entitled “Photons Across Medicine”, organized by Adam Wax, Duke University, highlighting activities of joint interest between the Optical Society of America (OSA) and the Society for Nuclear Medicine and Molecular Imaging (SNMMI). This paper is a synopsis of the presentations made at this joint symposium. Central to the special symposium presentations was the fact that the optical and nuclear imaging communities share common interests and challenges. These are highlighted in this article. Also discussed was the fact that the nuclear technologies in imaging have found their way into general clinical utility, a feat that has yet to be achieved by optical methods. Because of the common ground shared by the two technologies, coordination between the two societies should be planned.
---
paper_title: Review of biomedical Čerenkov luminescence imaging applications

paper_content:

Cerenkov radiation is a fascinating optical signal, which has been exploited for unique diagnostic biological sensing and imaging, with significantly expanded use just in the last half decade. Cerenkov Luminescence Imaging (CLI) has desirable capabilities for niche applications, using specially designed measurement systems that report on radiation distributions, radiotracer and nanoparticle concentrations, and are directly applied to procedures such as medicine assessment, endoscopy, surgery, quality assurance and dosimetry. When compared to the other imaging tools such as PET and SPECT, CLI can have the key advantage of lower cost, higher throughput and lower imaging time. CLI can also provide imaging and dosimetry information from both radioisotopes and linear accelerator irradiation. The relatively short range of optical photon transport in tissue means that direct Cerenkov luminescence imaging is restricted to small animals or near surface human use. Use of Cerenkov-excitation for additional molecular probes, is now emerging as a key tool for biosensing or radiosensitization. This review evaluates these new improvements in CLI for both medical value and biological insight.
---
paper_title: A solid state scintillation detector for high-energy charged particles

paper_content:

Abstract A completely solid state scintillation detector for high energy charged particles is described. The device consists of a scintillator, a photodiode to which the scintillator can be optically coupled, and a charged sensitive preamplifier, all mounted in a small tubular assembly. The viability of the device as a detector for use in nuclear and high energy physics is demonstrated, and its properties examined. Results are given with various scintillators stopping 48.8 MeV protons, the best energy resolution being 2% fwhm when CsI(Tl) is used.
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Title: A Review: Photonic Devices Used for Dosimetry in Medical Radiation

Section 1: Introduction
Description 1: Introduce the significance of radiation dosimetry in medical applications and provide a brief overview of the types of radiation and the need for precise measurement.

Section 2: Photodiodes/LEDs
Description 2: Discuss the characteristics, advantages, and types of photodiodes and LEDs used for radiation detection, including their structure and functionality.

Section 3: Structure
Description 3: Explain the atomic structure of semiconductor materials used in photonic devices, focusing on the bonding and doping processes, and how these affect their performance as dosimeters.

Section 4: Functionality and Operational Principle
Description 4: Describe the operational principle of photonic devices like LEDs and photodiodes, including electrical stimulation, electroluminescence, and biasing.

Section 5: Present Literature
Description 5: Review current research and findings on the use of photonic devices for medical radiation detection, including performance metrics, sensitivity, and calibration studies.

Section 6: Benefits, Limitations, and Challenges as Potential Dosimeters
Description 6: Evaluate the advantages and disadvantages of different photonic devices used in radiation dosimetry, addressing issues like sensitivity, accuracy, durability, and the impact of radiation-induced structural damage.

Section 7: Phototransistors
Description 7: Provide an overview of phototransistors and their application in radiation dosimetry, including their benefits, limitations, and performance compared to other photonic devices.

Section 8: Photovoltaic Sensors/Solar Cells
Description 8: Examine the use of photovoltaic sensors and solar cells in medical radiation detection, detailing their structure, operational principle, and performance.

Section 9: Charge-Coupled Devices (CCD)/Charge Metal Oxide Semiconductors (CMOS)
Description 9: Discuss the structure and operational principle of CCDs and CMOS, including their advantages and challenges in medical radiation detection.

Section 10: Summary
Description 10: Summarize the findings from the review, highlighting the most promising photonic devices for dosimetry and suggesting areas for future research and development.

Section 11: Conflicts of Interest
Description 11: Declare any potential conflicts of interest related to the review.