ABSTRACT
Background: Boron neutron capture therapy [BNCT] is a binary radiotherapy combining biochemical targeting with neutron irradiation. However, monitoring the boron distribution is a fundamental problem in BNCT. Prompt gamma rays emitted by boron capture reaction can be used to address the issue
Materials and Methods: The general-purpose Monte Carlo toolkits Geant4 and MCNP were used for the simulations. A cubic phantom with soft tissue was used to study the prompt gamma emission during BNCT. The Chinese hybrid phantom with arbitrary tumors was constructed and used to acquire the 0.478 MeV prompt gamma rays in BNCT. Tomographic images were reconstructed with the maximum likelihood expectation maximization [MLEM] algorithm
Results: Comparison between MCNP and Geant4 showed a similar gamma rays emission rate in soft tissue. Up to 30 gamma ray peaks were found in the simulation, and 0.478 MeV prompt gamma ray from boron was clearly observed. The single brain tumor with variable diameter from 1 cm to 4 cm in the heterogeneous anthropomorphic phantom was each time found to be recognizable in the reconstructed image. Furthermore, in a patient with four tumors, the variable distance between the source and the tumors leads to a neutron attenuation thus resulting in an inhomogeneous number of prompt gammas
Conclusion: The SPECT system for a heterogeneous phantom in BNCT was simulated with Geant4. The results show that BNCT-SPECT is valid for the reconstruction of the boron capture interaction position for a heterogeneous patient
ABSTRACT
Background: Boron neutron capture therapy [BNCT] is a radiotherapy that combines biological targeting and high linear energy transfer. A potential therapeutic approach for non-small cell lung cancer [NSCLC] is considered. However, dose in lung tumor is not homogeneous, and it will reduce the effect of BNCT treatment. In order to improve the dose distribution of BNCT, the multi-field irradiation strategy and its effects need to be explored
Materials and Methods: Common NSCLC model was defined in Chinese hybrid reference phantom and the boron concentration in skin and tumor varied from 6 to 18 ppm and from 30 to 65 ppm, respectively. Monte Carlo method for dose distribution calculation was used. Accelerator-based neutron source called [Neuboron source] was used and multi-field source irradiation plans were designed to optimize the dose distribution
Results: Under one-field irradiation, it was not feasible to perform BNCT, because the skin dose is unlikely to meet its dose limit. Under two- and three-field irradiation, the uniformity of tumor dose was improved and the maximum dose to organs at risk [OARs] decreased. If boron concentration in skin was between 6-18 ppm, BNCT was feasible with the boron concentration in tumor reaching about 57-60 ppm for two-field irradiation and 41-45 ppm for three-field irradiation, respectively
Conclusion: The multi-field irradiation plan could improve the dose distribution and the feasibility of BNCT for NSCLC. Theoretical distributions of Boron-10 were obtained to meet the treatable requirement of BNCT, which could provide a reference for NSCLC using BNCT in future multiple-field irradiation