Concept Verification of Three-Layer DOI Detectors for Small Animal PET

다국어 초록 (Multilingual Abstract)

<P> Improved spatial resolution without sacrificing sensitivity is one of the most challenging developmental goals for small animal PET scanners. The 3-layer configuration that we propose here utilizes relative offsets of half a crystal pitch in x- and y-directions, and pulse shape discrimination to obtain depth of interaction (DOI). Three layers of crystals with a dimension 1.5<TEX>$\,\times\,$</TEX>1.5<TEX>$\,\times\,$</TEX>7.0mm <TEX>$^{3}$</TEX> were composed of a L <TEX>$_{0.2}$</TEX> GSO (Lu<TEX>$_{0.4}$</TEX> Gd<TEX>$_{1.6}$</TEX> SiO<TEX>$_{4}$</TEX>: Ce) crystal layer and a L<TEX>$_{0.9}$</TEX> GSO (Lu<TEX>$_{1.8}$</TEX> Gd <TEX>$_{0.2}$</TEX> SiO<TEX>$_{4}$</TEX> : Ce) crystal layer aligned with each other, and a L <TEX>$_{0.9}$</TEX> GSO crystal layer offset at half a crystal pitch in x- and y-directions. The L<TEX>$_{0.9}$</TEX> GSO crystal layer was attached to a Hamamatsu H9500 flat-panel PMT. The devised small animal PET scanner has a diameter of 84 mm with one detector ring, and can be upgraded to two detector rings. GEANT4 Monte-Carlo simulation was used to estimate sensitivities of <TEX>$\sim 12\hbox{\%}$</TEX> and <TEX>$\sim 20\hbox{\%}$</TEX>, respectively, at the center of one and two PMT ring system with an energy window of 350 <TEX>$\sim$</TEX> 750 keV. We present flood images with peak-to-valley ratios of about 5–6 obtained using <TEX>$^{22}$</TEX> Na and layer identification capability of <TEX>$\sim 99\hbox{\%}$</TEX> with pulse shape analysis, and verified the basic concepts of multi-layer small animal PET. </P>