A dual detector β-ray imaging probe with γ-ray background suppression for use in intra-operative detection of radiolabeled tumors

The basic concepts for a dual detector β+ imaging probe incorporating a method of γ-ray background suppression were evaluated. The test devices consisted of a 1.2 cm2 β+ imaging CaF2(Eu) scintillator disk optically coupled to a 1.7 mm thick, area-matched transparent diffuser disk, which in turn was coupled to sets of 2×2 or 4×4 mm2 by 10 mm long BGO, GSO or LSO scintillators, which acted as both γ-detectors as well as light guides for the CaF2(Eu) scintillation light, which in turn are attached to a fiber optic bundle coupled to a multichannel photomultiplier. Pulse shape discrimination allowed identification of the detector of interaction and coincidence between the two detectors allowed selection of β+-only events. This type imaging detector system was shown to be capable of producing high-resolution images of β+ distributions while suppressing the events due to the 511 keV annihilation radiation background. GSO was found to be the detector of choice for this application.