Studies On System Performance And Image Reconstruction Of Full-coverage Small Animal PET System

In order to increase detectors space coverage for radioactive source, and thus toimprove detection sensitivity of Positron Emission Tomography, we propose a newstructure for PET system by adding two flat panel detectors onto both ends of originalcylindrical detector ring. In this thesis, the system performance and imagereconstruction methods for the proposed full coverage small animal PET system isstudied.The Monte Carlo simulation package GATE is used to build up the model andperform simulations for full coverage small animal PET system. We build up thecylindrical detector, add two flat panel detectors. and then generate single gammaphotons distribution map to validate the simulation model.To investigate the detection sensitivity of full-coverage small animal PET systemwith a hole in flat panel detector, we make Monte Carlo simulation with full coveragestructure. Three types of radioactive sources are used: point source, circular planesource and cylindrical source. Coincidences events are extracted from hits data, and bycounting the number of events the detection sensitivity is calculated. Results indicatethat as to full coverage system, the change of the detector structure can improve thesensitivity of animal PET system. The total number of coincidences is4.48times ofconventional micro PET, and the number of coincidences which are used to imagereconstruction is2.22times of micro PET. And the simulation results of point sourceand circular plane source show that full coverage small animal PET system make thewhole field of view more uniform which is good for data collection and imagereconstruction.SSRB data binning method is used to generate sinograms from simulated list-modeevents. A system matrix is calculated with siddon algorithm, and a MLEM iterativeimage reconstruction algorithm is implemented. The radioactive phantoms used arepoint source and small cylindrical source both located in the centre of FOV. Bycomparing the reconstruction images of both conventional micro PET and the fullcoverage structure PET system, it is reveal that: with DOI information of flat paneldetectors, the spatial resolution along radial direction is better than micro PET; forcoincidences detected by flat panel detectors, if one only uses those coincidence events which angle between LOR and PET ring axis is small enough, both the imagefluctuation due to noise and image uniformity are improved over conventional microPET.In conclusion, with appropriate method of image reconstruction, full-coveragesmall animal PET system can improve radial spatial resolution and uniformity ofreconstruction image. The new structure of detectors design is considerable.