High Resolution Imaging in a PET Scanner With Hybrid Depth of Interaction Detectors

Positron Emission Tomography (PET) is a molecular imaging modality capable of imaging trace amounts of radiolabeled molecules targeting biomarkers. Accurate PET studies of small targets require high image resolution, for example, imaging small objects such as cancer lesions in early detection. The utility of PET in breast cancer imaging is in staging and follow-up observations. Another application of PET is in the monitoring of response to treatment in breast cancer patients, which can be done since small changes in tumor metabolism can be measured using PET. However, for accurate monitoring high resolution and sensitivity is required. Another disease in which PET has been proposed as a potential diagnostic tool is Rheumatoid Arthritis (RA). It has been shown that PET can measure the degree of inflammation in the synovium compartment of joints. PET imaging can be used in pre-clinical research to study murine models of arthritis. However, imaging arthritic mouse paws poses a significant challenge, since a very high resolution is required to image the very small mouse paw joints. These PET imaging applications motivate the development of high resolution detectors. High resolution detectors should have depth of interaction (DOI) encoding capabilities to maintain resolution uniformity across the image. The focus of this work is the development and characterization of high resolution DOI capable PET detectors and scanners for breast imaging and mouse paw imaging. The two PET detectors presented in this work were composed of arrays with LSO crystals of 1.5 x 1.5 x 20 mm3 and 0.5 x 0.5 x 8 mm3 dimensions, coupled to a position sensitive photomultiplier tube on one end and an avalanche photodiode on the opposite end. The array with the smaller crystal pitch was used to build the mouse paw scanner called PawPET. The performance characterization of both detectors is presented in terms of their spatial, DOI, energy, and timing resolution. In this dissertation, a description of the scanner gantry design for the breast scanner and PawPET scanner are given along with descriptions of the fabrication techniques used such as rapid prototyping using 3D printing technology.