Design of a clinical brain SPECT based on optimized multi slit-slat collimation.
Doctoral thesis, UCL (University College London).
Parallel-hole collimators are the most widely used collimators in clinical SPECT imaging. However the performances of these collimators are limited in terms of efficiency and resolution, 0.01% and 1cm at 10cm distance from the detector face, respectively. Simultaneous optimisation is not possible due to existence of a fundamental trade-off between resolution and efficiency. Hence an alternative method of increasing efficiency without compromising resolution is necessary. Slit-slat collimator provides a better alternative to parallel-hole, due to their magnification power. The aim and objectives of this PhD work was to design and optimise a clinical brain SPECT system based on slit-slat collimation and a novel detector with silicon drift diodes (SDDs) readout providing 1mm intrinsic resolution. The system efficiency can be improved by increasing the number of slits, however as the number of slits increases, so does the multiplexing, which is the overlapping of the projections on the detector plane. We hypothesize that the reconstruction of multiplexed (MX) projections can be improved by addition of non-MX projections. We have proved this using simulation and shown that a gain in signal to noise ratio (SNR) (25.5%) corresponding to 43% reduction in acquisition time was achievable when non-MX projections were available. Several novel system designs that utilise the SDDs technology with mixed degrees of multiplexing have been evaluated. To enable experimental validation of the simulation work, a prototype slit-slat collimator was designed and built for a conventional gamma camera. Full calibration of the system was performed, the efficiency and resolution profiles were measured and studies of point sources, Jaszczak and Striatal phantoms were completed. The results of these studies confirmed the potential for multiplexing to improve image quality when used in conjunction with non-multiplexed projections with a maximum gain in SNR equivalent to of 50.6%.
|Title:||Design of a clinical brain SPECT based on optimized multi slit-slat collimation|
|Additional information:||Permission for digitisation not received|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Medical Sciences > Medicine (Division of)|
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