From nose to toes: Enabling dynamic preclinical whole body Na¹⁸F using ultra-fast and ultra-low dose digital photon counting PET/CT

Objectives: Dynamic PET imaging allows for acquisition of valuable spatio-temporal activity concentration measurements. Furthermore, enables in vivo tracking of the physiological biodistribution of the radiotracer. Dynamic PET acquisitions have been primarily performed in single-bed axial field-of-views (FOVs). Thus, dynamic PET has been primarily linked with organ/specific tumor types, as well as cardiac or neurological regional PET studies, where single-bed acquisitions are preferable. Therefore, there is an important unmet clinical need to translate static small FOV PET into dynamic whole-body (WB) acquisitions. Next-generation digital photon counting PET/CT systems will enable ultra-fast acquisition times and ultra-low doses, thus, enabling dynamic whole body PET. The aim of this study was to assess whole-body (WB) dPET imaging in a translational canine model utilizing Na¹⁸F. Methods: Fourteen healthy, adult male Beagles (weight (kg) mean ±SD; 14±1.54) were scanned. An average dose of 50 μCi Na¹⁸F was administered. Imaging initiated at the time of injection and covered 6 bed positions, acquiring 12 seconds per bed position for 15 consecutive whole body runs, lasting 35 minutes. All imaging was performed on a digital photon counting system (Philips Vereos). PET listmode data were reconstructed using a 576x576 matrix, producing a 1mm isometric voxel size; using point spread function and Gaussian filtering. Three iterations with 7 subsets were used for reconstructions. Three-dimensional (3D) regions of interest (ROI) were traced over the distal femur, first lumbar vertebra, and a portion of the liver, recording SUV_max. Results: All the scans and reconstructions were performed successfully for all the subjects. Dynamic whole body acquisitions were feasible; moreover, they showed excellent image quality. Qualitatively and quantitative assessment provided detailed insight into tissue/skeleton perfusion and bio-distribution characteristics. Quantitative outcome measurements were highly consistent among tissues/structures in all subjects. Conclusion: Next-generation digital PET allows for the development of new whole body screening imaging protocols, taking advantage of ultra-fast and/or ultra-low dose methodologies. Making use of very short acquisition times, whole body dynamic protocols in preclinical models are feasible and robust. Ultra-fast Na¹⁸F dynamic whole body bio-distribution exploration may enhance a more comprehensive diagnosis when imaging tumors characterized by bone metastatic lesions such as prostate, breast and lung tumors. The innovative imaging technique, together with the animal model may advance translational nuclear medicine imaging in order to apply to clinical patients and facilitate a thorough diagnosis, in addition to the standard static single FOV examination.