Development of a Prototype AWSM-PET Device for Augmented Whole-Body PET Imaging and Initial Human Study

Augmented whole-body scanning via magnifying PET (AWSM-PET) is a technology that aims to enhance the image resolution and sensitivity of the clinical PET/CT scanner for whole-body imaging. This study presents the system design, performance evaluation, and results from phantoms and initial human imaging studies. Methods: The AWSM-PET system integrates 2 high-resolution detector panels ("outserts") with a Biograph Vision PET/CT scanner (Siemens Healthineers). Positioned outside the scanner's axial field of view, each panel consists of 32 detector modules, each containing a 30 × 30 lutetium oxyorthosilicate crystal array (0.97 × 0.97 × 10 mm³ per crystal) at 1.05-mm pitch. These detectors are packaged and read out using the scanner's detector electronics assembly. Customized firmware and software were developed to establish the additional coincidence detection among the outserts and the scanner. The system acquires data simultaneously during a whole-body scan using continuous bed motion. List-mode-based image reconstruction software has been developed for AWSM-PET system using the continuous-bed-motion protocol. Performance was evaluated through sensitivity measurements, imaging of a mini-resolution phantom containing multiple groups of hot spheres, a National Electrical Manufacturers Association Image Quality (NEMA IQ) phantom study with custom small-diameter tumor inserts, and an initial human study. Results: The outsert detectors achieved an energy resolution of 11% at 511 keV. The coincidence resolving time between the outserts and between outserts and scanner was 183 and 211 ps full width at half maximum, respectively. Sensitivity increased by up to 18.4%, depending on the source location. Mini-resolution phantom images demonstrated higher peak-to-valley ratios for spheres with a diameter of 6 mm or less compared with native scanner images. In the NEMA IQ study, AWSM-PET achieved a higher contrast recovery ratio (CRC) for the smallest spheric lesion (diameter, 4.88 mm) across all CRC metrics (maximum, peak, and mean) but no improvement for larger lesions compared with high-resolution Biograph Vision images. Initial human imaging confirmed the system's compatibility with clinical workflows, achieving improved resolution in high-count regions, such as the brain. However, increased noise in low-count regions (e.g., abdomen) was observed and requires further improvement. Conclusion: The prototype AWSM-PET system demonstrated enhanced image resolution and sensitivity of a clinical PET/CT scanner without negatively impacting its performance, showing improved CRC and spatial resolution for small lesions in phantom and human imaging.