FLUKA simulation of target fragmentation in proton therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Physics

Background:

• Proton therapy utilizes proton beams for cancer treatment, but nuclear interactions generate secondary fragments.
• These fragments possess high Linear Energy Transfer (LET) and atomic numbers, differing significantly from primary protons.
• Secondary fragments deposit energy locally, potentially increasing the Relative Biological Effectiveness (RBE) and altering dose distribution, particularly impacting tissues near the Bragg peak.

Purpose of the Study:

• To characterize the mixed radiation field produced by target fragmentation in proton therapy.
• To evaluate the dose-averaged LET and RBE in a Spread Out Bragg Peak (SOBP) scenario.
• To inform the integration of target fragmentation data into treatment planning systems (TPS) for enhanced accuracy.

Main Methods:

• Monte Carlo simulations were used to model the nuclear interactions and resulting radiation field.
• FLUKA code was employed to determine the production cross-section of secondary fragments.
• Dose-averaged LET was calculated for a SOBP, and RBE was estimated using two phenomenological models.

Main Results:

• The study characterized the mixed radiation field, including dose-averaged LET and RBE, arising from target fragmentation.
• FLUKA simulations provided cross-section data essential for understanding fragment production.
• The findings highlight the significant radiobiological impact of secondary fragments on dose distribution and RBE.

Conclusions:

• Secondary fragments significantly influence dose distribution and RBE in proton therapy.
• Accurate modeling of target fragmentation is essential for improving treatment planning system accuracy.
• Future work includes developing a Monte Carlo database of fragment fluence for TPS integration.