cMiCE: a high resolution animal PET using continuous LSO with a statistics based positioning scheme

Objective: Detector designs for small animal scanners are currently dominated by discrete crystal implementations. However, given the small crystal cross-sections required to obtain very high resolution, discrete designs are typically expensive, have low packing fraction, reduced light collection, and are labor intensive to build. To overcome these limitations we have investigated the feasibility of using a continuous miniature crystal element (cMiCE) detector module for high resolution small animal PET applications. Methods: The detector module consists of a single continuous slab of LSO, 25 25mm in exposed cross-section and 4mm thick, coupled directly to a PS-PMT (Hamamatsu R5900-00-C12). The large area surfaces of the crystal were polished and painted with TiO2 and the short surfaces were left unpolished and painted black. Further, a new statistics based positioning (SBP) algorithm has been implemented to address linearity and edge effect artifacts that are inherent with conventional Anger style positioning schemes. To characterize the light response function (LRF) of the detector, data were collected on a coarse grid using a highly collimated coincidence setup. The LRF was then estimated using cubic spline interpolation. Detector performance has been evaluated for both SBP and Anger based decoding using measured data and Monte Carlo simulations. Results: Using the SBP scheme, edge artifacts were successfully handled. Simulation results show that the useful field of view (UFOV) was extended to B22 22mm with an average point spread function of B0.5mm full width of half maximum (FWHMPSF). For the same detector with Anger decoding the UFOV of the detector was B16 16mm with an average FWHMPSP of B0.9mm. Experimental results yielded similar differences between FOV and resolution performance. FWHMPSF for the SBP and Anger based method was 1.4 and 2.0mm, uncorrected for source size, with a 1mm diameter point source, respectively. Conclusion: A continuous detector module with an average FWHMPSF approaching one millimeter has been built and tested. Furthermore, the results demonstrate that our SBP scheme yields improved performance over traditional Anger techniques for our cMiCE detector. r 2002 Elsevier Science B.V. All rights reserved.