A Comparison of the Dose Distribution of Proton and X-ray Beams
With X-ray radiation therapy (black line), the radiation dose peaks soon after entering the body and often, long before reaching the tumor, gradually decreases. Healthy tissue surrounding the tumor receives much of the dose. With proton therapy (blue lines), treatment conforms more closely to the tumor, so that less radiation is deposited in the healthy tissue in front of the tumor compared to X-ray therapy, and almost none is deposited in the healthy tissue behind the tumor.