Alnaaimi, M.; (2011) Evaluation of the UCL Compton camera imaging performance. Doctoral thesis , UCL (University College London).

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Abstract

This thesis presents the imaging performance of the University College London (UCL) High Purity Germanium (HPGe) Compton camera. This work is a part of an ongoing project to develop a Compton camera for medical applications. The Compton camera offers many potential advantages over other imaging modalities used in nuclear medicine. These advantages include a wide field of view, the ability to reconstruct 3D images without tomography, and the fact that the camera can have a portable lightweight design due to absence of heavy collimation. The camera was constructed by ORTEC and the readout electronics used are based on GRT4 electronics boards (Daresbury, UK). The camera comprises two pixellated germanium detector planes housed 9.6 cm apart in the same vacuum housing. The camera has 177 pixels, 152 in the scatter detector and 25 in the absorption detector. The pixels are 4x4 mm2. The imaging performance with different gamma-ray source energies was evaluated experimentally and compared to the theoretical estimations. Images have been taken for a variety of test objects including point, ring source and Perspex cylindrical phantom. The measured angular resolution is 7.8° ± 0.4 for 662 keV gamma-ray source at 5 cm. Due to the limited number of readout modules a multiple-view technique was used to image the source distributions from different angles and simulate the pixel arrangement in the full camera. In principle, the Compton camera potentially has high sensitivity but this is not recognized in practice due to the limited maximum count rate. Although there are a number of limitations in the current prototype camera some potentially useful qualities have been demonstrated and distributed sources have been imaged. The key limitations in the current prototype are acquisition time, processing time and image viii reconstruction. However, techniques are available to significantly improve and overcome these limitations. This thesis presents the current state of the Compton camera performance along with a demonstration of its strengths and limitations as a potential candidate for nuclear medicine imaging.

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