How Do Ultrasound Machines Work?

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Medical ultrasonography, more commonly known as “ultrasound,” was first introduced into the medical world in the 1940s. In 1949, John Wilde used the technology to assess the thickness of patient’s bowel tissue. Six decades later, the technology is used on everything from taking a photo of an unborn child to therapeutic procedures like the drainage of fluid collections. Ultrasound diagnoses and treatments are being conducted by numerous medical fields, including but not limited to: cardiology, gastroenterology, neurology, obstetrics, and urology. The ultrasound has been widely accepted because of its ability to safely take photos of what is inside of people’s bodies. The technology also has advanced so it can be used for therapeutic treatments. Several common therapeutic applications that people commonly hear of are breaking up kidney stones, treating cysts and tumors, cataract treatment, and even teeth cleaning. John Wilde probably never expected the vast influence sonar would eventually have on the medical world.

How does an ultrasound machine work?

The ultrasound machine actually uses very basic technology, called sonar, which has been around for nearly 100 years. The idea is that when sound reflects off of an object people can translate that into understanding the size of the object and how far away it is. This is the same way a bat navigates through the dark, by listening to the sound echoes to see where objects are located. Originally, sonar was used to determine where underwater objects such as icebergs were located to help guide ships (the Titanic wreck provided the motivation behind technology advancement). Eventually, doctors realized that the use of higher frequencies of sound waves could penetrate the human skin and give people an image of what lies beneath.

An ultrasound machine requires two main tools in order to emit sound, listen to it, and translate it. The transducer probe with crystals and the ultrasound CPU are the tools needed to turn sounds into an image. The transducer is generally a hand held device that is used to emit sound waves to a specific location on the body and then listen for the echoes of the sounds after they are reflected off of different types of tissue in the body. The frequency of the sound wave and the time it took the echo to return to the transducer is sent to a computer that uses a mathematical equation to translate the sounds into a two-dimensional image. The further away objects will appear darker and the closer objects in the body will show up as brighter areas on the image. Lower frequencies are used for producing images of deeper objects such as a liver or kidney and higher frequencies are used for softer tissue and superficial structures like muscles, tendons, testes, breasts, and the neonatal brains.
Although no risks have been reported for diagnostic ultrasound procedures, the, “as low as reasonably achievable,” (ALARA) method is used to determine what frequency of sound should be used, assuming risks could be greater with higher frequencies.


  • Non-invasive procedure that is completely painless: Like any non-invasive procedure, the patient will not have any scarring, bruising, pain, or recovery period.
  • Easily accessible: Every hospital and clinic should have access to an ultrasound machine and usually will have an experienced ultrasound technician. There are also many small and portable machines that could be purchased for private use in your home.
  • Low cost: The procedure is generally very low cost compared to other imaging technologies such as magnetic resonance imaging and computed X-ray tomography.
  • No radiation side effects: Since no radiation is used in the process, any side effects generally associated with radiation are non-existent.
  • No reported harmful short or long term side effects: The most profound benefit is that no patients have had any serious side effects from the procedure, making it one of the safest diagnostic and therapeutic medical devices available.
  • Real-time imaging assists in guiding invasive procedures and enabling rapid diagnosis of any changes.
  • It shows the structure of organs: This gives the technician a good idea of what exactly is happening inside your body at that precise moment.


  • Cannot clearly reflect images of organs that are surrounded by gas such as the lungs.
  • Cannot penetrate bone, making it difficult to get sonar imaging of the brain and other organs protected by bone.
  • Depth of sonar is slightly limited and may have difficulty taking deep images of obese patients.

A well experienced operator is required to acquire good quality images and make an accurate diagnosis.