The PennPET Explorer Scanner for Total Body Applications

A high-performance TOF PET scanner is being developed with a very large axial FOV as part of the Explorer consortium. The primary goal is to develop a research instrument intended for the exploration of new clinical applications as well as to further the understanding of the bio-distribution of tracers. We describe the development and preliminary performance of the University of Pennsylvania's prototype scanner, which is being constructed initially with 3 rings for an axial FOV of 70 cm to test the design, with potential expansion to 140 cm with 6 rings or 210 cm with 9 rings. Each ring is based on the Philips tile detector; an array of 8*8 LYSO scintillation crystals, each of which is 3.86*3.86*19 mm
³
, coupled in a 1-to-1 configuration to the PDPC dSiPM sensor which has 64-channels of 4 mm
²
devices. Individual tiles are assembled onto a detector module in 7 rows axially and 4 columns in the transverse direction. These are constructed in a ring of 18 modules with a transverse diameter of 76.4 cm and an axial extent of 22.9 cm per ring. Compared to the commercial implementation (the Philips Vereos PET/CT), the ring has a modified cooling design using chilled water to achieve a temperature on the tiles below 20°C. Our research system also differs from the commercial system in writing singles event data from each ring, which will be synchronized to ensure that singles events can be combined from any combination of rings and sorted off-line into coincidence pairs. We have completed and tested operation of 2 rings, and the construction of the 3
^rd
ring is underway. Initial measurements indicate an energy resolution of 12% and timing resolution of 330 ps, both taken at a temperature of about 20°C. In addition we have acquired and reconstructed images of uniform cylinders and the NEMA IEC phantom, which indicates very good uniformity and image quality. A more thorough performance characterization will be done once the 3
^rd
ring is operational.