Possibility analysis of bremsstrahlung x-ray imaging of C-14 radionuclide using a LaGPS radiation imaging system

The in-vivo imaging of C-14 is thought to be impossible because it is a pure beta-emitting radionuclide and the energy of beta particles is low. However, beta particles emit bremsstrahlung x-rays in subjects that may be imaged from the outside subjects. Thus, we imaged bremsstrahlung x-rays from a C-14 solution using a high resolution Ce-doped (Gd, La)₂Si₂O₇ (LaGPS) radiation imaging system. With a LaGPS radiation imaging system, we conducted bremsstrahlung x-ray imaging from a C-14 solution in a plastic container with 37 MBq radioactivity with and without a parallel hole collimator. Without it, images were obtained with a spatial resolution of ∼1 mm FWHM in less than 1 min of acquisition time. The energy spectrum of the bremsstrahlung x-rays from a C-14 solution showed a broad distribution with an average energy of ∼30 keV. With a parallel hole collimator, images of the C-14 solutions were also possible although the detected counts decreased to 2.4% of those without a collimator. The measured sensitivities of the LaGPS imaging system without and with a collimator for bremsstrahlung x-rays from C-14 solutions in a plastic container were 3.5 × 10^-5 and 8.5 × 10^-7, respectively. We conclude that the imaging of bremsstrahlung x-rays from C-14 might be a new method for the in-vivo distribution imaging of small animals or plants.