Depth of interaction detection for γ-ray imaging☆

Abstract A novel design for an inexpensive depth of interaction capable detector for γ -ray imaging has been developed. The design takes advantage of the strong correlation between the width of the scintillation light distribution in monolithic crystals and the interaction depth of γ -rays. We present in this work an inexpensive modification of the commonly used charge dividing circuits which enables the instantaneous and simultaneous computation of the second order moment of light distribution. This measure provides a good estimate for the depth of interaction and does not affect the determination of the position centroids and the energy release of γ -ray impact. The method has been tested with a detector consisting of a monolithic LSO block sized 42 × 42 × 10 mm 3 and a position-sensitive photomultiplier tube H8500 from Hamamatsu. The mean spatial resolution of the detector was found to be 3.4 mm for the position centroids and 4.9 mm for the DOI. The best spatial resolutions were observed at the center of the detector and yielded 1.4 mm for the position centroids and 1.9 mm for the DOI.