Therapeutic Radiology  Radiation therapy is commonly used to
treat brain tumors. Some, such as germinomas can be cured and
others such as malignant gliomas are slowed in their
progression. The target for radiation-induced cell death is the
genetic information within the cell, the DNA molecule. High-
energy beams cause breaks in the DNA. The effect of radiation
depends on the dose applied, how often it is applied and how
much time is available for the target to repair the damage.
Dividing cells (such as tumor cells) are more susceptible to
irradiation than non-dividing cells.  Photons are the most
commonly used particles in the radiotherapy of brain tumors.
Examples for non-photon irradiation modalities (available in
experimental facilities) are neutrons, protons, helium ions,
pions and heavy ions (carbon, argon, neon).  External beam
radiation therapy  Most commonly radiation therapy is provided
by a machine called linear accelerator (LINAC), which uses high-
frequency electromagnetic waves to accelerate electr