In this work, magnetic resonance (MR) compatible small animal PET detectors with high image resolution, high sensitivity and low cost were designed and developed.

The Imaging Research Laboratory at University of Washington developed the continuous miniature crystal element (cMiCE) detector and a statistics-based positioning (SBP) algorithm. In this work, methods were developed to improve the SBP algorithm. An experimentally measured X/Y resolution of 1.57-mm full width half maximum (FWHM) and a depth of interaction (DOI) resolution of 3.65-mm FWHM have been achieved for a 15-mm thick cMiCE detector. A Cramer-Rao lower bound (CRLB) study shows that the measured X/Y resolution was close to the CRLB, while the DOI CRLB was overly optimistic.

A sensor-on-entrance-surface (SES) design using silicon photomultiplier (SiPM) arrays was proposed to improve the cMiCE detector performance. Simulation results indicate that the SES design could improve the X/Y/DOI resolution by more than 20% compared to conventional backsided readout. Optimum positioning performance of the SES cMiCE detector requires the SiPM array to be kept at a constant temperature preferably below room temperature.

A semi-analytical algorithm was developed to evaluate the image quality of a whole PET scanner based upon single detector module performance in the scenario of multiple realizations. The results show that by including scanner system response function (SRF) in reconstruction and using our newly proposed SES design for cMiCE detector, better quantitation task performance could be achieved for the scanner without degrading the detection task performance.

Besides the cMiCE detector, we are also working on the development of a high spatial resolution, high sensitivity, compact PET detector for small animal PET/MR imaging. The key design features are the use of trapezoidal slat crystals (TSC) and SiPM arrays. TSC crystals are used to support high detector packing fraction, to provide the high resolution characteristics of a discrete crystal detector, and to maintain the intrinsic DOI positioning capability of a continuous crystal detector. SiPM arrays are used for magnetic field compatibility and compactness. For a 12-mm thick TSC detector, the spatial resolution is 0.72-mm FWHM in X, 0.84-mm FWHM in Y and 1.74-mm FWHM in DOI for a simulation study.