Development and Evaluation of mini-EXPLORER: A Long Axial Field-of-View PET Scanner for Nonhuman Primate Imaging

Abstract

We describe a long axial field-of-view (FOV) PET scanner for high-sensitivity and total-body imaging of nonhuman primates and present the physical performance and first phantom and animal imaging results. The mini-EXPLORER PET scanner was built using the components of a clinical scanner reconfigured with a detector ring diameter of 43.5 cm and an axial length of 45.7 cm. National Electrical Manufacturers Association (NEMA) NU-2 and NU-4 phantoms were used to measure sensitivity and count rate performance. Reconstructed spatial resolution was investigated by imaging a radially stepped point source and a Derenzo phantom. The effect of the wide acceptance angle was investigated by comparing performance with maximum acceptance angles of 14°-46°. Lastly, an initial assessment of the in vivo performance of the mini-EXPLORER was undertaken with a dynamicF-FDG nonhuman primate (rhesus monkey) imaging study. The NU-2 total sensitivity was 5.0%, and the peak noise-equivalent count rate measured with the NU-4 monkey scatter phantom was 1,741 kcps, both obtained using the maximum acceptance angle (46°). The NU-4 scatter fraction was 16.5%, less than 1% higher than with a 14° acceptance angle. The reconstructed spatial resolution was approximately 3.0 mm at the center of the FOV, with a minor loss in axial spatial resolution (0.5 mm) when the acceptance angle increased from 14° to 46°. The rhesus monkeyF-FDG study demonstrated the benefit of the high sensitivity of the mini-EXPLORER, including fast imaging (1-s early frames), excellent image quality (30-s and 5-min frames), and late-time-point imaging (18 h after injection), all obtained at a single bed position that captured the major organs of the rhesus monkey. This study demonstrated the physical performance and imaging capabilities of a long axial FOV PET scanner designed for high-sensitivity imaging of nonhuman primates. Further, the results of this study suggest that a wide acceptance angle can be used with a long axial FOV scanner to maximize sensitivity while introducing only minor trade-offs such as a small increase in scatter fraction and slightly degraded axial spatial resolution.

Mini EXPLORER II: a prototype high-sensitivity PET/CT scanner for companion animal whole body and human brain scanning

“…Figure 8 demonstrates that no significant artifacts are apparent in a 20 cm diameter uniform cylinder with length adequate to encompass the entire AFOV. Figure 9 demonstrates excellent spatial resolution even with all lines of response accepted-a result that is in agreement with what was seen with MiniEXPLORER I (Berg et al 2018).…”

Total-Body PET and Highly Stable Chelators Together Enable Meaningful 89Zr-Antibody PET Studies up to 30 Days After Injection

“…There have been several recent developments in high-sensitivity PET systems that are suitable for human and nonhuman primate imaging (1)(2)(3)(4). In these scanners, substantial sensitivity gains have been achieved by extending the scanner's axial length up to approximately 2 m for a human imaging system and to approximately 50 cm in preclinical systems.…”

“…In these scanners, substantial sensitivity gains have been achieved by extending the scanner's axial length up to approximately 2 m for a human imaging system and to approximately 50 cm in preclinical systems. In this study, we have used the primate mini-EXPLORER PET system, a 45-cm-long system with National Electrical Manufacturers Association NU-2 sensitivity of approximately 50 kcps/MBq, which is capable of imaging the entire body of young rhesus monkeys in a single bed position (1,5).…”

PennPET Explorer: Human Imaging on a Whole-Body Imager

“…Spence et al previously estimated k 4 in gliomas and in normal brain with imaging up to 8 h (7). Berg et al demonstrated washout from the brain in rhesus monkey studies (22). We are currently pursuing kinetic analysis studies to estimate k 4 over the extended period of imaging.…”