%0 Journal Article %A Ramsey Badawi %A Weiping Liu %A Eric Berg %A Yang Lv %A Tianyi Xu %A Shaohui An %A Yun Dong %A Xuezhu Zhang %A Martin Judenhofer %A Jinyi Qi %A Terry Jones %A Alice Tarantal %A Jun Bao %A Hongdi Li %A Simon Cherry %T Progress on the EXPLORER project: towards a total body PET scanner for human imaging %D 2018 %J Journal of Nuclear Medicine %P 223-223 %V 59 %N supplement 1 %X 223Objectives: Long axial field of view PET for humans offers the promise of a step-change in molecular imaging research and clinical practice. The EXPLORER Consortium is developing two such systems - one, academically based at UC Davis, will be capable of total-body imaging at high spatial resolution, and the other, academically based at U Penn, will be capable of complete torso imaging at high time-of-flight resolution. In addition, we have developed two mini-EXPLORER scanners that allow us to (1) test all the components of the total-body scanner prior to full scale-up and (2) test a variety of applications in nonhuman primates. In this work we report progress in development of the total-body scanner together with examples of applications developed on the mini-EXPLORER scanners. Methods: Mini-EXPLORER Scanners: Mini-EXPLORER I, based on Siemens mCT detectors, with an axial field of view of 45 cm and with sensitivity at the center of the field of view of ~15%, has been installed in the Multimodal Imaging Core at the California National Primate Research Center at UC Davis. Mini-EXPLORER II, built by United Imaging Healthcare, utilizes exactly the same PET system components as those that are being used to build the total-body system. Mini-EXPLORER II has an axial field of view of 48.3 cm, a NEMA NU2 spatial resolution of 2.6 mm and has a sensitivity at the center of the field of view of ~16%. Mini-EXPLORER II has a 16-slice clinical CT for attenuation correction and PET/CT image fusion. Mini-EXPLORER II was shipped at the end of 2017 and installation is planned at the UC Davis School of Veterinary Medicine. Total-body Human EXPLORER: Fabrication of this device is well under way. The PET scanner will consist of 8 rings of 24 detector modules for a total axial field of view of 194 cm and a bore diameter of 76 cm. Each module consists of 5x14 detector blocks. Each block is an array of 6x7 LYSO scintillator crystals of size of 2.76x2.76x18.1 mm3, coupled to a 2x2 array of 6x6 mm2 SensL J-series SiPMs. For the detector modules that will be used, an average energy resolution of 11.7 ± 1.5% has been measured, with timing resolution of 409 ± 39 ps. Measurements of module rate capability, together with anthropomorphic simulations, suggest that the total-body scanner should be able to scan an adult human with approximately 10 mCi of uniformly distributed activity at a system dead-time of approximately 10%.The PET scanner will be coupled to a CT scanner with 80 detector rows covering 40 mm axially, and a rotation time of 0.3 sec. Fabrication is expected to be completed by May 2018. Applications in Nonhuman Primates: Late time-point scanning: a rhesus monkey was injected with 2.5 mCi of 18F-FDG and scanned dynamically for 60 minutes. It was then scanned again at 18 hours post-injection (PI). Total-body scanning: a young rhesus monkey was injected with 1.8 mCi of 18F-PBR111 and imaged dynamically for 90 minutes. A third rhesus monkey was injected with 2.8 mCi of 11C-raclopride and scanned dynamically for 90 minutes. Results Late time-point scanning: At the late time-point (10 half-lives PI) for the FDG scan, much of the brain and cardiac activity had washed out. Total-body scanning: Of particular interest in the 18F-PBR111 images, focal uptake was observed in the wrists and shoulders of the animal. In the 11C-raclopride images, significant uptake was seen in the basal ganglia as expected, and also in the liver and gastrointestinal tract. We are currently undertaking kinetic analysis of these data. Conclusions Fabrication of the world’s first total-body PET imaging system for humans is well under way. Experience with mini-EXPLORER systems suggests that imaging will be possible at high spatial resolution, high sensitivity, and with a large dynamic range. There is also preliminary evidence that imaging at late time-points and with the entire body in the field of view will yield new scientific insights. Acknowledgements Support for this work includes NIH grants CA206187, CA170874, and OD011107. %U