EXTERNAL BEAM RADIATION
FOR MANY CANCERS AND OTHERS
External beam radiation is the most common radiation technique used to treat malignant tumors throughout the body. It includes the delivery of high energy x-rays (photons), electrons, and low energy superficial x-rays. The high energy photon beam is used most commonly, as this beam is able to penetrate deep into the body and spare more superficial tissues, especially the skin. Photon beam radiation is used to treat cancers of the breast, prostate, lung, brain, head + neck, bone, GI tract, uterus, and others.
The device that generates and delivers the high energy photon beam for cancer treatment is the linear accelerator. The linear accelerator is capable of rotating around a patient lying on a treatment table allowing treatment of a tumor from several angles. This allows the delivery of high doses of radiation to the tumor while reducing the dose to surrounding normal tissues. Treatments are completely painless and take only 5 – 15 minutes. Treatments are typically given once daily, 5 days a week, for several weeks.
To shield the regions around the tumor that need to be protected from the radiation, the radiation oncologist ordinarily designs blocks that are constructed from a lead-like alloy. Our linear accelerators have 120 leaf multi-leaf collimators, which are computer controlled devices that accurately perform this shielding function. This does away with the need for alloy blocks and allows the treatments to be performed more quickly and efficiently.