Purpose: Boron neutron capture therapy (BNCT) is a selective therapy at the cell level, utilizing mainly thermal neutron interaction with boron-10 in tumor cells. Our final goal is to develop a system that enables dose optimization by optimally modulating the neutron beam for each patient, taking into consideration the target shape and location and the surrounding healthy tissues. The aim of this study was to evaluate the feasibility of modulating neutron beam intensity using a three-dimensional (3D) printed compensator.
Methods: We developed a material jetting 3D printing system with a robust nanocomposite hydrogel. To assess the shielding effect of the 3D printed hydrogel compensator for neutron beam, test slabs were fabricated. The thickness and clay nanoparticles concentration of the test slabs were varied from 3 to 35 mm and 2.5 to 5 wt%, respectively. The irradiation experiment was performed using the standard epithermal neutron irradiation mode of the Heavy Water Neutron Irradiation Facility at Kyoto University Research Reactor (KUR-HWNIF). Gold wires were used to estimate the neutron flux at the entrance and exit plane of the test slabs. Thermo-luminescent dosimeters were used for the estimation of gamma-ray doses. The measured data were normalized by the values at the entrance plane of the test slabs.
Results: The relative neutron flux at the exit plane of test slabs of 3, 5, 10, 20, and 35 mm thickness were 67, 74, 71, 47, and 25%, respectively, and the relative gamma-ray doses were 98, 113, 104, 97, and 82%, respectively. The relative neutron flux at the exit plane of the test slabs decreased and the relative gamma-ray doses increased with increase in the clay nanoparticles concentration.
Conclusion: Our results demonstrated the feasibility of utilizing the 3D printed compensator to modulate the neutron beam intensity for BNCT.
Funding Support, Disclosures, and Conflict of Interest: This research was partially supported by JSPS KAKENHI Grant Number JP17K15800 and a research grant from Ricoh Co., Ltd., Kanagawa, Japan.