Development of GGAG alpha camera system for targeted alpha radionuclide therapy research

Abstract

Cerium doped Gd3(GaAl)5O12 (GGAG) scintillator has a character in which the decay time for alpha particles differs from that of gamma photons. This is a good point for an imaging detector used for alpha autoradiography of a mouse administered Astatine-211 (At-211) in radionuclide therapy research. Thus, we developed an alpha camera system using a GGAG imaging detector combined with a charge-coupled device (CCD) camera. Our GGAG imaging detector is made of a 0.5 mm-thick GGAG plate optically coupled to a position sensitive photomultiplier tube (PSPMT) and set in a stand with the CCD camera positioned on the upper side of the imaging detector to take optical photos. We first measured the performance of our alpha camera system using an Am-241 alpha source and natural alpha emitting radionuclides with radon daughters. We then conducted imaging of the non-sliced organs of a mouse. After the imaging detector surface was covered with 2.5 µm-thick Mylar film, the organs of the At-211-administered mouse was set on the imaging detector after split or opened and the alpha emitter distributions were measured. We used pulse shape analysis to separate the alpha particles from the beta particles or gamma photons. We successfully measured the alpha particle distributions of the wet non-sliced organs of the At-211-administered mouse. Using the pulse shape spectrum, we could separate the alpha particle images and beta particle or gamma photon images. We conclude that the developed alpha camera system is promising for the imaging of alpha particles and separating of the images using pulse shape discrimination.