What kind of radiation is used in RapidArc?
Photons (X-rays) are used to deliver RapidArc. The radiation is generated by a machine called a medical linear accelerator. This machine stands approximately nine feet tall, is nearly 15 feet long and can be rotated around the patient with amazing precision. Operationally, microwave energy, similar to that used in satellite television transmission, is used to accelerate electrons to nearly the speed of light. As they reach maximum speed they collide with a tungsten target, which in turn releases photons, or X-rays. Very small beams with varying intensities can be aimed at a tumor from multiple angles to attack the target in a complete three-dimensional manner. In fact, RapidArc can be delivered with beams the size of 2.5 x 5-millimeter pixels—the size of a pencil tip—each with varying intensity. The idea is to deliver the lowest dose possible to the surrounding healthy tissue, while still delivering the maximum dose to the tumor.
