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Boron Neutron Capture Therapy (BNCT) is facing a renaissance with the development of accelerator-based neutron sources in different countries [1,2]. These facilities can be placed in hospitals, overcoming the main barrier in the expansion of this promising therapy, which up to now has been only performed at research reactors. BNCT is the only external radiotherapy option which is selective at the cellular level and is delivered in just one day, without any fractioning.
These new facilities are based on the production of neutrons by means of proton collisions on lithium or berillium targets, then, the produced neutron beam is moderated and collimated by a beam shaping assembly (BSA) providing an adequate neutron beam for the patient treatment. Each BSA must be specifically designed for each combination of proton energy and neutron production target (example in Ref. [3]). This allows to adjust the neutron spectrum in the optimal epithermal energy region. The spectrum is key in the dose delivered to the patient, both at the tumor and at the organs at risk.
There are different nuclear data needs for the improvement of the different elements involved in the therapy. First, there are different neutron interactions with the most common materials of the BSA (especially inelastic scattering processes) that are key for optimizing the final spectrum by means of Monte Carlo simulations. In addition, the cross sections of other neutron induced reactions of interest for the dosimetry and experimental spectrometry via multiactivation in the epithermal range are also not well known. Finally, the dose calculation at tumor and normal tissues requires accurate (with less than 5% uncertainty) data of the most important reactions leading to energy releases. In this sense, the n_TOF collaboration has recently measured the cross sections of the reactions 14N(n,p), 35Cl(n,p) and 35Cl(n,g) of interest for the determination of the normal tissue absorbed dose, especially at skin and brain.
In this contribution other cross sections corresponding to reactions of interest for BNCT will be mentioned and the current knowledge on them will be analysed.
[1] A.J. Kreiner et al., Present status of Accelerator-Based BNCT, Rep. Pract. Oncol. Radiother. 21, 95-101 (2016).
[2] I. Porras et al., Perspectives on Neutron Capture Therapy of Cancer, in Proceedings of the 15th International Conference on Nuclear Reaction Mechanisms, edited by F. Cerutti, A. Ferrari, T. Kawano, F. Salvat-Pujol, and P. Talou, CERN-Proceedings-2019-001 (CERN, Geneva, 2019), pp. 295-304.
[3] P. Torres-Sánchez, I. Porras, N. Ramos-Chernenko, F. Arias de Saavedra and J. Praena, Optimized beam shaping assembly for a 2.1-MeV proton-accelerator-based neutron source for boron neutron capture therapy. Sci Rep. 11:7576 (2021) https://doi.org/10.1038/s41598-021-87305-9