Medical Linear Accelerators are the key systems used for delivering radiotherapy treatments. Standing approximately nine feet tall by nearly 15 feet long and weighing as much as 18,700 pounds, the accelerator consists of four major components: an electronics cabinet called a “stand,” housing a microwave energy generating source; a rotating gantry containing the accelerator waveguide; an adjustable treatment couch; and operating electronics. Accelerators are located within specially constructed concrete treatment rooms to provide x-ray shielding.

A Linear Accelerator is a highly specialized machine in which a high frequency (alternating) electric field is used to accelerate electrons, producing high energy x-rays (photons) and electrons.

In operation, an Electron Gun with a tungsten filament produces electrons, which ride on microwaves (produced by a Klystron amplifier) down an accelerating Waveguide at nearly the speed of light (186,000 miles per second). A powerful Bending Magnet is used to select the appropriate electron energy (measured in millions of electron volts (MeV)) and send these electrons to impact on a thin heavy metal target producing photons (deeply penetrating X-rays). With a flip of a switch, the electrons may bypass the target and hit a Scattering Foil to generate a beam of electrons used for non-penetrating or superficial treatments, such as in the treatment of skin cancer.  On the way to the patient, the chosen type of radiation beam is made flat and symmetric by using a Flattening Filter with quadrant monitor chambers. The dose is monitored using ionization chambers, and the beam is constrained and shaped using the 120 leaf Multi-Leaf Collimator, to cover only the projected target area. These beam modifications correlate with the therapy plan produced by the CMS XiO Treatment Planning computer to give the proper sculpted radiation dose to the tumor.