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

Abstract

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) 2 Si 2 O 7 (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.

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

“…The spatial resolution for bremsstrahlung X-rays from H-3 water was lower than that for bremsstrahlung X-rays from C-14 solution (1 mm FWHM). The main reason for the low spatial resolution was the low energy of the bremsstrahlung X-rays from H-3, which had 10-keV energy -one third of the average energy of bremsstrahlung X-rays from C-14 solution [14] because the spatial resolution of the Anger principle based camera is roughly determined by the light output of the scintillators [21]. Another reason was that our LaGPS imaging detector had a larger FOV with an FP-PMT with a larger anode size (6 mm × 6 mm).…”

“…Another reason was that our LaGPS imaging detector had a larger FOV with an FP-PMT with a larger anode size (6 mm × 6 mm). The LaGPS imaging detector used for the bremsstrahlung X-rays from C-14 solution had a cross-wire anode with 4-mm separations [14].…”

“…Detecting bremsstrahlung X-rays is one possible method of imaging beta-emitting radionuclide from outside of subjects because X-rays can penetrate the subjects or containers. So far, we successfully imaged bremsstrahlung X-rays outside of a plastic container of carbon-14 (C-14) solution that emitted beta particles (maximum energy: 156 keV) [14] using our developed highresolution Ce-doped (Gd, La) 2 Si2O 7 (LaGPS) radiation imaging system [15]. However, since the energy of the bremsstrahlung X-rays emitted from H-3 is much lower than those of C-14, it would be a challenge to image the bremsstrahlung X-rays emitted from H-3 water.…”