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Towards High Sensitivity and High Spatial Resolution Positron Emission Tomography Imaging


High sensitivity and high resolution have been pursued as some of the most important research goals for preclinical Positron Emission Tomography (PET) imaging. PETbox4, a new, fully tomographic bench top PET scanner dedicated for mouse imaging, was designed and developed in this work. The aim of the PETbox4 scanner is to achieve very high sensitivity and produce high quality PET tomographic images for molecular imaging based biomedical research. Performance of the prototype PETbox4 system was characterized using the National Electrical Manufacturers Association (NEMA) NU 4-2008 standards.

Due to the different characteristics caused by the compact geometrical factors, PETbox4 requires data acquisition protocols that differ from those optimized for conventional large diameter ring systems. In this work the energy window for data acquisitions with PETbox4 was optimized using the Geant4 Application for Tomographic Emission (GATE) simulation. A lower level discriminator (LLD) of 350 keV was proposed as the optimized energy threshold.

Pulse pileup is a common problem in multiplexed scintillator detectors readout by resistor divider networks. In this work, a new pileup rejection method named position shift rejection (PSR) is introduced. The PSR method is based on the detection of position shifts on event location as the signal is being integrated. Both simulations and physical measurements show that PSR performs more accurate rejection and avoids erroneous rejection and loss of sensitivity compared to the conventional leading edge rejection (LER) method.

A new phoswich DOI Detector with crystal scatter identification capability is being designed and developed for implementation in a next generation small animal PET system at UCLA. Both simulations and measurements were performed to evaluate the characteristics and benefits of the proposed design. In conclusion, these results demonstrate that the proposed detector is feasible and can potentially lead to a high spatial resolution, high sensitivity and DOI PET system.

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