Neutron beams for accelerator based boron neutron capture therapy using the near threshold 7Li(p,n) reaction

D.M. MINSKY; A.J. KREINER

San Martín, Provincia de Buenos Aires

Congreso; XII Argentinean Meeting of Medical Physics, I Meeting of Medical Physics of the Americas & I AATMN Meeting of Nuclear Medicine and Diagnostic Imaging; 2014

Sociedad Argentina de Física Medica - Universidad de San Martín

(Congreso en 2014, publicación en 2015) Introduction: Boron Neutron Capture Therapy (BNCT) is a radiation therapy modality under development for the treatment of certain types of cancer. BNCT consists in two steps. In the first step the stable isotope 10B is loaded into the tumor cells. In the second step, the patient is irradiated with neutrons of enough energy so that they can reach the tumor with thermal energies. Neutrons are captured in boron and two charged particles are emitted ?a 7Li ion and an a particle- with ranges of the order of the cell size and they produce a very localized lethal effect. The success of BNCT depends on two factors: the selectivity  of the boron carrier to target tumor cells and the neutron beam quality. Our group is working on the neutron beam generation for BNCT based on ion accelerators.   Objectives: This work  deals with the development of neutron sources for BNCT using ion accelerators and based on the lithium on  proton reaction working at energies near the reaction threshold. The objective is to maximize the tumor dose without exceeding the healthy tissues constraints.   Material and Methods: Energy spectra and angular distributions of neutrons produced by the reaction have been calculated with the corresponding double differential cross sections. A neutron production target with its cooling system and a head Snyder phantom have been considered in transport simulations. An A-150 plastic charged with 6Li has been used as bolus. The coupled neutron and photon simulations have been made with the MCNP5 code with  which depth dose profiles have been calculated in the head phantom. Bombarding energy and irradiation angle have been varied in order to maximize the tumor dose without exceeding healthy tissues tolerances and an irradiation time of 60 minutes.   Results: Several combinations of irradiation angles and bombarding energies yield  very good tumor doses ((≥50 RBEGy) and 57 RBEGy has been reached with one of them. These doses are equivalent to those obtained in the best BNCT facility based on nuclear reactors but with ion accelerators which are much simpler and less costly.   Conclusions: Results show very good doses to tumor with near-threshold 7Li(p,n)-based BNCT and consolidates the use of accelerators for this radiation therapy modality.