Favorable ballistic properties of protons

The interest of protons is mainly ballistic.

A proton is a heavy charged particle that deposits energy along its trajectory before stopping abruptly at some point, where it delivers maximum energy. Beyond this point, tissues receive essentially no radiation.  In addition, protons are heavy particles that tend to go straight (little lateral side scatter), resulting in only a small dose deposited in tissues bordering the tumor.

Clinical advantages of protons

To eliminate a tumor, a so-called "tumoricide" dose needs to be delivered to kill the cells. However, some tumors are located very close to radiation-sensitive organs. Such tumors can therefore not be treated using X-rays with the necessary dose, as sensitive organs would receive too high a dose for their tolerance.

Since protons do not irradiate tissues beyond a given depth and because the dose delivered in tissues bordering the beam is small, they enable to reach the optimal dose in the tumor without going over the maximum acceptable dose for healthy surrounding and adjacent tissues.

The main advantage is thus to reduce the risk of subsequent side effects that may appear between a few weeks and several years after irradiation.

Author / Source : Proton Therapy Center