TY - JOUR T1 - Evaluation of scatter effects in phoswich detector modules of a dedicated small animal PET scanner JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1501 LP - 1501 VL - 50 IS - supplement 2 AU - Jianhua Yu AU - Martin Pomper AU - Benjamin Tsui Y1 - 2009/05/01 UR - http://jnm.snmjournals.org/content/50/supplement_2/1501.abstract N2 - 1501 Objectives The goal is to evaluate the effect of photon scatter within the phoswich detectors, or detector scatter (DS), on resolution and quantitative accuracy of a commercial small animal PET scanner using Monte Carlo (MC) simulation. Methods The phoswich detector consists of 7mm thick LYSO and 8mm thick GSO scintillators. Line-of-response data were MC simulated from a point source placed in 4mm increments along the central axis and in 5mm increments along a transaxial radius. Both 250-700keV and 400-700keV energy windows (EW) with and without DS were modeled, and DS with and without depth-of-interaction (DOI) correction were compared. System resolution, in terms of FWHM, was determined from the 2D OS-EM reconstructed image of the point source. Recovery coefficients (RC) from 3D regions-of-interest (ROI) with different diameters were calculated. Results The radial, tangential and axial resolution obtained with 250-700keV EW showed differences of 7%, 7% and 4%, respectively, between that with and without DS when averaged over different axial locations; and 10%, 7% and 2% when averaged over the radial locations. The RC for point sources along the central axis reached 95% at 12.0mm and 9.2mm ROI diameters for 250-700keV and 400-700keV EW with DS, and at 2.5mm for both EW without DS. The RC for point sources modeled with and without DOI correction differed by <5% when ROI >6mm. Conclusions DS has larger effect on the radial and tangential than the axial resolution for a small animal PET scanner with phoswich detectors. It has significant effect on the PET quantitation due to the long tail of point response function. The effect of DS can be reduced with a narrower EW at the expense of lower counts. DOI correction has small effect in reducing DS. Research Support This work was funded in parts by NIH grant CA92781 and EB1558. ER -