System characteristics comparison of the Walk-Through Total-Body PET and the Biograph Vision Quadra PET/CT

Abstract Background: Although a new generation of tomographs with a larger axial field of view called total-body PET has been developed, they are not widely utilized due to their high cost compared to conventional scanners. The walk-through total-body PET scanner is introduced as a high-throughput and cost-efficient alternative to total-body PET scanners, by making use of a flat-panel geometry and lower cost, depth-of-interaction capable, monolithic BGO detectors. The main aim of the presented study is to evaluate the system characteristics of the walk-through total-body PET scanner by comparing it with the Siemens Biograph Vision Quadra total-body PET. Methods: The walk-through total-body PET is comprised of two flat detector panels, spaced 50 cm apart. Each panel, 70 x 106 cm^2 in size, consists of 280 BGO-based monolithic detectors. The Biograph Vision Quadra, one of the most common total-body PET scanners with 106 cm of axial field-of-view, is constructed with pixelated LSO scintillation crystals. The spatial resolution, sensitivity, count rate performance, scatter fractions and image quality of both scanners are simulated in the GATE simulation toolkit for comparison. Results: Due to the DOI-capable detectors used in the walk-through total-body PET, the spatial resolution of this scanner was below 2 mm in the entire volume of the tomograph. This resolution is a large improvement compared to the values of the Quadra. This feature allows the walk-through total-body PET to use its maximum sensitivity (∼ 26%) for data acquisition and image reconstruction. While the Biograph Vision Quadra has a higher primary sensitivity (∼ 31.5%), after applying an 85 maximum ring difference cut to limit axial resolution loss, the corresponding value dropped by a factor of three (∼ 11.2%). Conclusion: Based on the excellent combination of very good spatial resolution and high sensitivity of the walk-through total-body PET, along with a 2.2 times lower scintillation crystal volume and 1.8 times lower SiPM surface, this scanner can be a very cost-efficient alternative for total-body PET scanners.