Optical density analysis in autoradiographic images from BNCT protocols

Abstract

In Boron Neutron Capture Therapy (BNCT) research, information on spatial distribution and concentration of boron in tissues is essential for the treatment planning and for dose determination. Neutron autoradiography technique offers the possibility to gain insight into boron biodistribution in tissues. The irradiation of tissue sections deposited on nuclear track detectors produces damages in the latter, which can be visualized by microscope imaging and that are spatially correlated with the boron localization in the biological section. We had previously developed a methodology for the quantification of boron concentration in tissue samples by nuclear track density determination (QTA). In this work we analyzed the optical density (OD) in autoradiographic images where track density is too high to be quantified by track counting. OD was determined from grey level measurements on low magnification micrographs and proved to be a suitable parameter to quantify boron concentration. The images were originated by placing polycarbonate detectors in contact with samples containing 10B atoms, irradiated with thermal neutrons and finally chemically attacked. Reference standards were developed from aqueous solutions prepared with known boron concentrations in order to construct calibration curves. The obtained optical density values were compared with curves proposed by other authors, showing similar tendencies. The calibration curve was used to make preliminary boron concentration determinations in histological tissue sections of animals infused with boron compounds, which agreed with measurements realized by the QTA approach. The methodology proposed in this work would allow a fast preliminary analysis of histological and autoradiographic images in samples of interest for BNCT.