Performance Evaluation of Small Animal PET Scanners With Different System Designs

This study evaluated the image quality metrics of small animal PET scanners based upon measured single detector module positioning performance. A semi-analytical approach was developed to study PET scanner performance in the scenario of multiple realizations. Positron range blurring, scanner system response function (SRF) and statistical noise were included in the modeling procedure. The scanner sensitivity map was included in the system matrix during maximum likelihood expectation maximization (MLEM) reconstruction. Several image quality metrics were evaluated for octagonal ring PET scanners consisting of continuous miniature crystal element (cMiCE) detector modules with varying designs. These designs included 8 mm and 15 mm thick crystal detectors using conventional readout with the photosensors on the exit surface of the crystal and a 15 mm thick crystal detector using our proposed sensor-on-the-entrance (SES) design. For the conventional readout design, the results showed that there was a tradeoff between bias and variance with crystal thickness. The 15 mm crystal detector had better detection task performance, while quantitation task performance was degraded. On the other hand, our SES detector had similar detection efficiency as the conventional design using a 15 mm thick crystal and had similar intrinsic spatial resolution as the conventional design using an 8 mm thick crystal. The end result was that by using the SES design, one could improve scanner quantitation task performance without sacrificing detection task performance.