Human Research Studies on the PennPET Explorer

Objectives: The increased detection sensitivity afforded by the extended axial coverage of whole-body PET imagers can be leveraged for numerous clinical and research applications. We previously demonstrated such abilities on the prototype PennPET Explorer with a 64-cm axial field-of-view (AFOV). We have since expanded the scalable PennPET Explorer to an AFOV of 1.12 m and human imaging has commenced with the goal of utilizing this device as a research scanner. This study is intended to demonstrate the benefits of the expanded AFOV.

Methods: Human imaging on the PennPET Explorer can be performed through three mechanisms. (1) As part of a clinical standard-of-care (SOC) PET/CT scan, subjects will be imaged on the PennPET Explorer without administration of additional radiotracer; an FDA-approved radiotracer will be utilized in these cases. (2) Subjects enrolled in another research study may be imaged on the PennPET Explorer, with the specific radiotracer and protocol dictated by the concomitant research study. (3) Subjects may be imaged with an FDA-approved radiotracer, without concomitant SOC imaging, with an injected activity that may be less than that used for SOC imaging.

Results: Human imaging of clinical subjects with ¹⁸F-FDG on the PennPET Explorer with expanded AFOV demonstrated qualitatively superior image quality compared to SOC PET imaging. Compared to the prototype configuration, image quality was similar, but maintained over a larger axial range. Of note, the 1.12-m AFOV extends from the vertex to the proximal thigh in a single bed position in most patients and includes all major organs. Initial studies included delayed ¹⁸F-FDG imaging of cancer patients, demonstrating superb image quality with scan durations of 10 minutes. A biopsy-proven lung cancer demonstrated increased contrast compared to blood pool on the delayed PennPET scan compared to a SOC scan. A research study that utilized 1 mCi of ⁸⁹Zr-Df-IAB22M2C, an anti-CD8 minibody, demonstrated excellent image quality at 24 hours post injection in a 30 minute scan. Conclusion: Human imaging studies on the recently expanded 1.12-m AFOV PennPET Explorer have validated this device as a powerful research instrument. Delayed imaging of a biopsy-proven lung cancer demonstrated findings highly suspicious of malignancy, to a much greater extent than earlier SOC imaging. Delayed imaging with ⁸⁹Zr-Df-IAB22M2C supported the utility of tracers labeled with this long-lived radionuclide to track extended biological processes. With all major organs contained within the AFOV, and imaged with high sensitivity, additional studies with novel radiotracers will focus on optimizing the acquisition protocols for particular applications involving cancer, cardiac and neurological diseases, and immunology, facilitating translation of this class of long AFOV PET scanners. Acknowledgements: NIH R01-CA-225874, NIH R01-CA-113941, NIH KL2-TR-001879. ⁸⁹Zr-Df-IAB22M2C was kindly provided by ImaginAb, Inc., Inglewood, CA.