Room: AAPM ePoster Library
Purpose: To investigate the secondary thermal neutron production from ten different charged particles for the application of gadolinium (Gd) based tumor dose enhancement  and particle neutron gamma-x detection technique (PNGXD) .
Methods: We simulated using MCNP6 (Vr.6.1.1), a 5-10 cm spread-out Bragg peak (SOBP) for ten different particles on a 30×30×30 cm3 phantom of ICRU Soft Tissue. The ten charged particles included protons, helium, carbon, nitrogen, oxygen, neon, silicon, argon, antiprotons and negative pions. A 2 cm3 Gd solution with a concentration 3 mg/g representing a tumor was located in the middle of the SOBP.
Results: For a baseline comparison, protons were simulated and produced approximately 1.5×1011 neutron captures in Gd per Gy of dose (captures/Gy) or 1.4x1011 neutron captures per GyE (Gray Equivalent) of RBE weighted dose. Three particles, antiprotons, negative pions, and helium particles, produced a greater amount of Gd neutron captures per Gy than protons. The three particles resulted in 2.7×1012, 5.7×1012 and 2.5×1011 neutron captures per Gy of dose or 1.3×1012, 2.3×1012, 1.7×1011 neutron captures per GyE, respectively. Except for antiprotons, negative pions, and helium particles, a decrease in neutron production per Gy of dose with an increase in atomic number was observed.
Conclusion: From this study, it was determined that antiprotons, negative pions and helium ions can cause a greater amount of neutron captures in Gd per Gy or per GyE than protons. Helium ions may be the most clinically attractive option in terms of Gd neutron capture dose enhancement and spectroscopic tumor localization from the Gd contrast agent.
Funding Support, Disclosures, and Conflict of Interest: My work is supported by the Natural Sciences and Engineering Research Council of Canada Discovery Grant program RGPIN-2017-04386, and The Ryerson University Dean Research Fund-Research Tool and Instrumentation.