A 5 inch diameter position-sensitive scintillation counter

Recent developments in photomultiplier technology have enabled the construction of 5-in-diameter position-sensitive scintillation counters. A 5-in-diameter hard X-ray imager has been built and a position resolution of 4.0 mm full width half maximum (FWHM) has been obtained at 122 keV using a standard 3-mm-thick, 125-mm-diameter NaI(Tl) crystal with a 100-mm-diameter exit window. The spatial resolution can be improved by making some simple changes in the crystal design. The results show that the light output and spatial resolution vary considerably over the surface of such a detector. In order to make the best use of the imaging capability of these tubes, individual photon events must be corrected both in energy and position. The results of a 300-point detailed survey of the characteristics of the position-sensitive detector demonstrate its overall performance. A thyroid phantom image was obtained using this imager.<
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