In-hospital neutron autoradiography for Boron Neutron Capture Therapy applications

Abstract

Boron Neutron Capture Therapy (BNCT) is an experimental radiotherapy technique exploiting the reaction ¹⁰B(n,α)⁷Li to deliver a dose to the tumor sparing the healthy tissues: dedicated molecules are used to introduce the boron selectively in the tumor cells, which are irradiated with a thermal-epithermal neutron beam. There are two main limitations preventing BNCT from becoming a large-scale therapy: the availability of the neutron sources (that for their intensity and energy spectrum are strictly limited to nuclear reactors) and the specificity of the drugs used as boron carriers (i.e. their ability to concentrate only in the cancer cells and not in the bloodstream or in the healthy tissues).

In the framework of the INFN PhoNeS (Photo-Neutron Source) project, aimed at producing a neutron source for a hospital environment, a new imaging system for the analysis of boronated samples was developed: ¹⁰B imaging and quantitation is in fact a basic tool for the research on new boron carriers and for a better understanding of the existing ones. The imaging measurements are performed via neutron auto-radiography, detecting the α particles produced in the thermal-neutron irradiation of the boron samples with a micro-strip silicon detector, obtaining a 1-dimensional ¹⁰B distribution. Unlike the standard autoradiography techniques, this is a real-time method (able to provide results in times ranging from a few minutes to a hour, depending on the boron concentration) in a hospital environment (the neutrons are photo-produced by the 18 MV photons of a standard radiotherapy linac). The system was characterized and tested with several kinds of inorganic as well as biological samples (such as urine and blood) in order to obtain kinetic curves, that is the concentration of ¹⁰B as a function of time from the carrier uptake; thanks to a calibration with ¹⁰BSH, also quantitative analyses are possible.