A miniature phoswich detector for gamma-ray localization and beta imaging

A combined /spl gamma/-ray probe//spl beta//sup /spl plusmn// imaging detector was created by modification of a beta imaging intra-operative probe. This phoswich detector consists of a thin CaF/sub 2/(Eu) /spl beta//sup /spl plusmn// imaging disk, coupled through a light diffuser to 7 or 19 parallelepiped high-scintillation crystals arranged hexagonally in columns. These elements are either 2/spl times/2/spl times/10 mm/sup 3/ or 4/spl times/4/spl times/10 mm/sup 3/ LSO, GSO or BGO crystals, and act as both light guides for the imaging light and as intrinsic /spl gamma/-detectors. The coincidence between the CaF/sub 2/(Eu) and phoswich scintillators identifies PC or true /spl beta//sup -/ events and suppresses accompanying annihilation or background /spl gamma/-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 investigated 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 /spl gamma/-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 /spl gamma/-emitting radionuclides with the modestly directional, self-collimated phoswich crystals; (2) high resolution /spl beta//sup m/aging or coarse (annihilation background corrupted) /spl beta//sup +/ imaging in singles mode; or (3) /spl beta//sup +/ imaging in coincidence mode with reduced /spl gamma/-background contamination.