How does proton therapy work and how does it allow us to treat your tumor with millimeter precision?
The highly complex process begins inside the cyclotron, a 90-ton machine that separates protons from hydrogen gas and accelerates them to two-thirds the speed of light. You will not see the cyclotron when you come for treatment because the enormous machine is located behind the treatment rooms.
The accelerated proton particles are transported through a vacuum proton beamline from the cyclotron to the treatment rooms. Magnets focus the beam size during transport and guide the protons to a nozzle in the treatment room. The proton beam can be delivered either in a fixed horizontal gantry or by a 360-degree rotational gantry, a large device that moves around you during your treatment. The beam is delivered to one room at a time, with its energy and dose customized for you according to your personalized treatment plan.
The gantries are large too—each one is nearly 39 feet in diameter and weighs nearly 200 tons. The front of the gantry is visible inside our treatment rooms 1, 2, and 3 and can rotate 360 degrees around you, delivering the proton beam with sub-millimeter precision to treat your tumor. In our fourth treatment room, called the fixed beam room, the gantry does not rotate. Instead, the treatment table moves as needed for your specific treatment plan.
During your treatment sessions, we will use pencil beam scanning, which can deliver intensity-modulated proton therapy (IMPT), the most advanced type of proton therapy available anywhere. The radiation will be “painted” onto the tumor and treatment area in 3D—layer by layer, spot by spot—delivering prescribed dose levels to the desired volume of the target. The protons will deposit most of their energies at a planned depth inside your body (known as the Bragg peak), based on images of your tumor from a CT scan, and spare all of your normal tissues beyond the tumor from the unnecessary incidental radiation that is delivered with traditional radiation therapy.