Over the past few years, integrated positron emission tomography/magnetic resolution imaging (PET/MRI) systems emerged with great potential by providing added value that exceeds the sum of each system. However, the system’s overall cost has impeded the widespread adoption of PET/MRI and, furthermore, limited research opportunities for finding more clinical applications. To enhance the dissemination of PET/MRI, a brain-dedicated PET insert that can be inserted into any existing MRI for simultaneous PET/MRI was developed in our lab. This cost-effective PET insert with a better imaging performance could improve the adoption of PET/MR and allow more clinical and research opportunities in the Neurology field.

This thesis focuses on the development of an RF-penetrable brain-dedicated PET insert;​ (a) design and performance evaluation of the 1st-generation PET insert prototype are described, (b) its limitations and strategies for design improvements are explained, and (c) design and preliminary performance evaluation of the upgraded 2nd-generation PET insert prototype are presented.

The 1st-generation RF-penetrable PET insert prototype that allows the RF field from the MRI body coil to penetrate through small inter-module gaps showed promising results indicating that we can achieve simultaneous PET/MRI without modifying the existing MRI hardware. Nonetheless, some minor issues including the gradient-induced eddy current and low SNR MR image from receive attenuation were observed. These issues could be solved by (a) replacing the solid copper shield with a phosphor bronze mesh shield which has high RF shielding effectiveness and negligible induced eddy current and (b) placing a phased-array RX-only RF coil inside the PET insert for high SNR MR images while preserving the PET performance. With these modifications, the 2nd-generation RF-penetrable PET insert has been designed with a longer scintillation crystal axial FOV (16 cm for a full brain) for better sensitivity that enables it to be practical for clinical brain imaging. Preliminary results of one detector module have been collected and analyzed and overall performance of the MR system and the PET detector module was preserved.