The analysis of the distribution and density of nuclear tracks forming an autoradiography in a nuclear track detector (NTD) allows the determination of B atoms concentration and location in tissue samples from Boron Neutron Capture Therapy (BNCT) protocols. This knowledge is of great importance for BNCT dosimetry and treatment planning. Tissue sections studied with this technique are obtained by cryosectioning frozen tissue specimens. After the slicing procedure, the tissue section is put on the NTD and the sample starts drying. The thickness varies from its original value allowing more particles to reach the detector and, as the mass of the sample decreases, the boron concentration in the sample increases. So in order to determine the concentration present in the hydrated tissue, the application of corrective coefficients is required. Evaporation mechanisms as well as various factors that could affect the process of mass variation are outlined in this work. Mass evolution for tissue samples coming from BDIX rats was registered with a semimicro analytical scale and measurements were analyzed with software developed to that end. Ambient conditions were simultaneously recorded, obtaining reproducible evaporation curves. Mathematical models found in the literature were applied for the first time to this type of samples and the best fit of the experimental data was determined. The correlation coefficients and the variability of the parameters were evaluated, pointing to Page's model as the one that best represented the evaporation curves. These studies will contribute to a more precise assessment of boron concentration in tissue samples by the Neutron Autoradiography technique.

Boron Neutron Capture Therapy (BNCT) is a cancer treatment option that combines preferential uptake of a boron compound in tumor and irradiation with thermal neutrons. For treatment planning, boron concentration in different tissues must be considered. Neutron Autoradiography using Nuclear Track Detectors (NTD) can be applied to study both boron concentration and microdistribution in tissue samples. Histological sections are obtained from frozen tissue by cryosectioning. When they reach room temperature, they undergo an evaporation process, which leads to an increase of boron concentration in the sample. In order to take this effect into account, certain correction factors (Evaporation Coefficients, CEv) must be applied. With this aim, a protocol was established in order to register and analyze mass variation of tissue sections, measured with a semimicro scale. Values of ambient temperature, pressure and humidity were simultaneously recorded. Reproducible results of evaporation curves and CEv values were obtained for different tissue samples, which allowed the systematization of the procedure. This study contributes to a more precise determination of boron concentration in tissue samples through the Neutron Autoradiography technique, which is of great relevance to make dosimetric calculations in BNCT.

Boron Neutron Capture Therapy (BNCT) is a cancer treatment option that combines preferential uptake of a boron compound in tumor and irradiation with thermal neutrons. For treatment planning, boron concentration in different tissues must be considered. Neutron Autoradiography using Nuclear Track Detectors (NTD) can be applied to study both boron concentration and microdistribution in tissue samples. Histological sections are obtained from frozen tissue by cryosectioning. When they reach room temperature, they undergo an evaporation process, which leads to an increase of boron concentration in the sample. In order to take this effect into account, certain correction factors (Evaporation Coe cients, CEv) must be applied.With this aim, a protocol was established in order to register and analyze mass variation of tissue sections, measured with a semimicro scale. Values of ambient temperature, pressure and humidity were simultaneously recorded. Reproducible results of evaporation curves and CEv values were obtained for different tissue samples, which allowed the systematization of the procedure. This study contributes to a more precise determination of boron concentration in tissue samples through the Neutron Autoradiography technique, which is of great relevance to make dosimetric calculations in BNCT.