We have proposed a novel edge-readout detector design for PET, which can easily provide sub-millimeter in-plane spatial resolution together with DOI information with resolution determined by the thickness of the crystal layers. Multiple factors that can potentially affect the coincidence resolving time (CRT) have been studied in this work. The result indicates there is a strong correlation between the coincidence resolving time and the parameters of a constant fraction discriminator (CFD), while the correlation between CRT and other factors such as inclusion of optical barriers, locations of gamma-ray interactions in the detector and light-coupling material’s refractive index (between crystal and SiPM’s silicon substrate) is weak. With optimum CFD parameters, a 200-ps CTR can be achieved.
We have explored a method of using the side surfaces of a thin monolithic scintillation crystal for reading out
scintillation photons. A Monte-Carlo simulation was carried out for an LYSO crystal of 50:8mmx50:8mmx3mm
with 5 silicon photomultipliers attached on each of the four side surfaces. With 511 keV gamma-rays, X-Y spatial
resolution of 2:10mm was predicted with an energy resolution of 9:0%. We also explored adding optical barriers
to improve the X-Y spatial resolution, and an X-Y spatial resolution of 786um was predicted with an energy
resolution of 9:2%. Multiple layers can be stacked together and readout channels can be combined. Depth-of-
interaction information (DOI) can be directly read out. This method provides an attractive detector module
design for positron emission tomography (PET).
The adaptive single-photon emission computed tomography (SPECT) system studied here acquires an initial scout image to obtain preliminary information about the object. Then the configuration is adjusted by selecting the size of the pinhole and the magnification that optimize system performance on an ensemble of virtual objects generated to be consistent with the scout data. In this study the object is a lumpy background that contains a Gaussian signal with a variable width and amplitude. The virtual objects in the ensemble are imaged by all of the available configurations and the subsequent images are evaluated with the scanning linear estimator to obtain an estimate of the signal width and amplitude. The ensemble mean squared error (EMSE) on the virtual ensemble between the estimated and the true parameters serves as the performance figure of merit for selecting the optimum configuration. The results indicate that variability in the original object background, noise and signal parameters leads to a specific optimum configuration in each case. A statistical study carried out for a number of objects show that the adaptive system on average performs better than its nonadaptive counterpart.
We have developed a GPU-accelerated SPECT system simulator that integrates into instrument-design work flow . This simulator includes a gamma-ray tracing module that can rapidly propagate gamma-ray photons through arbitrary apertures modeled by SolidWorksTM-created stereolithography (.STL) representations with a full com- plement of physics cross sections [2, 3]. This software also contains a scintillation detector simulation module that can model a scintillation detector with arbitrary scintillation crystal shape and light-sensor arrangement. The gamma-ray tracing module enables us to efficiently model aperture and detector crystals in SolidWorksTM and save them as STL file format, then load the STL-format model into this module to generate list-mode results of interacted gamma-ray photon information (interaction positions and energies) inside the detector crystals. The Monte-Carlo scintillation detector simulation module enables us to simulate how scintillation photons get reflected, refracted and absorbed inside a scintillation detector, which contributes to more accurate simulation of a SPECT system.