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UBC Theses and Dissertations

Ga-67 imaging with vector Shirmohammad, Maryam


Ga-67 decays with emission of gammas of 93 (42%), 184 (21%), 300 (17%) and 393 (5%) keV. The energy range of the gammas of Ga-67 may impact the quality of the SPECT imaging data in a collimator type-dependent way. The MILABs VECTor is a preclinical SPECT scanner utilizing multi-pinhole collimators (MPC). Several MPCs can be mounted on the camera. A General Purpose Multi-Pinhole (GPMP), a High Energy Clustered Multi-Pinhole (HECMP), and a High Sensitivity Multi-Pinhole (HSMP) collimator were used for this work. The main objective of this thesis is the performance characterization of the VECTor and MPCs in imaging Ga-67. The sensitivity profiles of the MPCs, and uniformity and contrast metrics in the acquired images were evaluated for this purpose. Other objectives include evaluation of the attenuation and scatter correction, and finally optimization for Ga-67 imaging which includes proper selection of a MPC and the photopeaks for data reconstruction. Our results showed that the peak sensitivity of the GPMP, HECMP, and HSMP collimators at (93, 184, 300, 393 keV) is respectively (0.2%, 0.3%, 0.3%, 0.4%), (0.4%, 0.3%, 0.2%, 0.2%), and (1.8%, 1.6%, 1.0%, 0.8%). Ga-67 images have the best uniformity when the HECMP collimator is used for data acquisition. The integral uniformity of the images with the GPMP, HECMP, and HSMP collimators at (93, 184, 300, 393 keV) is respectively (24%, 26%, 62%, 83%), (17%, 18%, 22%, 38%), and (49%, 45%, 42%, 56%). The best contrast at 93 and 184 keV is obtained using the GPMP collimator, and at 300 and 393 keV is obtained using the HECMP collimator. The attenuation and scatter correction methods are performing well for Ga-67 data. Finally, only the first two photopeaks should be used with the GPMP and the HSMP collimators, and all the four photopeaks should be used with the HECMP collimator for the image reconstruction. In addition, GPMP collimator should be the collimator to be used for Ga-67 studies since the images with this collimator have the best contrast at 93 and 184 keV and for object sizes < 0.85 mm.

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