A feasibility study of the post-irradiation dose estimation with SPECT technique for BNCT

Various radioactive nuclei are generated in and around the target volume after the irradiation for boron neutron capture therapy. By measuring and estimating the distributions of these nuclei with the technique of single photon emission computed tomography (SPECT), more accurate post-irradiation dose-estimation can be expected. The feasibility study was performed mainly by simulation. The radioactivity densities for Cl-38, Ca-49 and Na-24 just after the irradiation were calculated to be 100-1000 Bq/cm(3) in and around the target volume. It was confirmed that these nuclei could be detected by SPECT under some conditions. Using the density differences for these generated nuclei, discrimination between soft-tissue area and bone area can be achieved. In focusing on the shallower 1cm(3) voxel, the necessary counting-time for Na-24 was estimated to be a few tens of minutes when the distance between the SPECT detector and the voxel was shortened to 6 cm.