Imaging of bremsstrahlung X-rays from tritium water in a plastic bag using a LaGPS radiation imaging system

Tritium (H-3) is a pure beta-emitting radionuclide and beta particles have extremely low energy (maximum energy: 18.6 keV). Thus the in-vivo imaging of H-3 is thought to be impossible. However, beta particles emit bremsstrahlung X-rays in subjects that may be imaged from outside of the subjects. We tried to image the bremsstrahlung X-rays from H-3 water using a newly developed radiation imaging system. The developed imaging system used a pixelated Ce-doped (Gd, La)2Si2O7 (LaGPS) scintillator plate optically coupled to a flat-panel position-sensitive photomultiplier tube (FP-PMT). Using the imaging system, we conducted bremsstrahlung X-ray imaging from H-3 water in a plastic bag with 37-MBq radioactivity. We obtained tungsten slit mask images with a spatial resolution of ~3 mm full width at half maximum (FWHM). The energy spectrum of the bremsstrahlung X-rays from the H-3 water showed a broad distribution with an average energy of ~10 keV. The measured sensitivities of the LaGPS imaging system for bremsstrahlung X-rays from H-3 water in a plastic bag were 1.8 × 10−7. We conclude that the imaging of bremsstrahlung X-rays from H-3 water was really possible and it has a potential to be a new method for the in-vivo H-3 imaging of small animals, plants, or materials.