Secondary particle dose in proton beam therapy computed using the LAHET code system

The objective of this study was to use the LAHET Code System (LCS), which has recently been used in shielding calculations for proton therapy, to model the neutron and photon dose equivalent distributions created in tissue during proton beam cancer therapy. Proton beams used for therapy have shown distinct advantages over other therapeutic radiation treatments due to the rapid distal dose fall-off in the region of the Bragg Peak. Nuclear reactions caused by the primary proton beam in beam modifying devices and patient tissues create secondary particles that contribute to the dose received by the patient inside and outside the targeted region. The spatial distribution of the dose created by these secondary particles is an important consideration in the choice of beam modification methods and treatment volume planning because a goal of radiation therapy is to minimize dose to normal tissue while maximizing dose to the tumor.