Proton Beam Therapy at OSF Healthcare's Peoria Cancer Institute. 

Dr. James McGee is the director of the oncology service line. He says proton beam therapy allows for “pencil” radiation treatment.
"[Protons] enter the body, give up a little bit of energy, and then go a certain distance based on their energy,” McGee said. “And then they just stop and give up all their energy, where they stop, that’s called the Bragg peak. And that's a characteristic we can use to increase the intensity of radiation to certain tumors, but in virtually all cases, restrict the dose of radiation to normal tissues.”