A Miniature Phoswich Detector for Gamma-ray Localization and Beta Imaging

A combined y-ray probe@* imaging detector was created by modification of a beta imaging intra-operative probe. This phoswich detector consists of a thin CaF,(Eu) p*imaging disk, coupled through a light diffuser to 7 or 19 parallelepiped highZ scintillation crystals arranged hexagonally in columns. These elements are either 2 x 2 ~ 1 0 mm3 or 4 x 4 ~ 1 0 mm3 LSO, GSO or BGO crystals, and act as both light guides for the imaging light and as intrinsic y detectors. The coincidence between the CaF,(Eu) and phoswich scintillators identifies p’ or true pevents and suppresses accompanying annihilation or background y events. The phoswich crystals are in turn coupled through optical fibers to a multi-channel PMT with positioning and discrimination electronics. Various characteristics of this novel imaging phoswich detector are inves-tigated and presented for each of the phoswich combinations including: detector anisotropy, effects of time blocking and energy windows on phoswich imaging, intrinsic singles and phoswich spectral and spatial resolution characteristics, and phoswich imaging ability within y background environments. The performance characteristics of the assembled prototype devices demonstrate that in surgery, this device can be used three ways: (1) rapid localization of y emitting radionuclides with the modestly directional, self-collimated phoswich crystals; (2) high resolution pimaging or coarse (annihilation background corrupted) p’imaging in singles mode: or (3) p’ imaging in coincidence mode with reduced y background contamination.