Ultra-fast Whole-body Na18F PET/CT using digital photon counting PET technology: A Clinical Feasibility Study

497 Objectives: For routine non-oncologic and oncologic bone imaging evaluation, sodium fluoride-18 (Na18F) PET/CT is used clinically for the detection, assessment and characterization of osteoblastic lesions. A current clinical challenge for patients with symptomatic osseous disease is that whole-body Na18F PET image acquisition times (60 - 120 s/bed) are longer than desired and necessitate novel approaches to substantially reduce PET image acquisition time. The recent introduction of digital photon counting PET (dPET) detectors in clinical PET/CT systems enables new imaging approaches with faster PET image acquisition times and/or PET imaging with reduced radiotracer doses. The objective is to develop and assess the clinical feasibility of a 10x faster, whole-body Na18F dPET imaging approach for the detection and evaluation of osteoblastic lesions and compare to standard PET image acquisition times. Methods: In this feasibility trial, investigational whole-body Na18F dPET/CT imaging (Vereos, Philips Healthcare) was performed in 10 oncologic patients using a target Na18F dose of 185 MBq. At 75 min post injection, whole-body dPET acquisition was performed using a substantially faster 9 s/bed (1/10 of the standard PET acquisition time) followed by a standard 90 s/bed acquisition at 80 min post injection. Standard definition dPET image data sets (voxel volume = 4x4x4 mm3) were reconstructed using Time-of-Flight and evaluated by matched pair comparison for lesion detectability, overall image quality and background quality by a blinded reader panel using an Intellispace Portal workstation. Results: All 20 data sets were rated as evaluable for qualitative assessment of 18F biodistribution and osteoblastic lesions. Visually, faster 9 s/bed dPET acquisitions demonstrated comparable 18F-avidity in both normal bone and osteoblastic lesion conspicuity when compared to standard 90 s/bed acquisitions. There were no instances of discordant osteoblastic lesions between the 9 s/bed and 90 s/bed acquisitions. Average SUVmean values were comparable for 9 s/bed and 90 s/bed acquisitions in terms of background skeletal muscle (0.7 ± 0.1 and 0.7 ± 0.1, respectively) and normal vertebral bone (6.6 ± 1.3 and 7.3 ± 1.3, respectively). Average SUVmax values of 7 18F-avid osteoblastic lesions were also comparable for 9 s/bed and 90 s/bed acquisitions (39 ± 30.2 and 46.1 ± 38.3, respectively). It is very likely that physiologic clearance of 18F activity from skeletal muscles and continued 18F uptake in normal bone/osteoblastic lesions occurred between the initial 9 s/bed and subsequent 90 s/bed acquisitions. No statistically significant differences in the average SUVmean or SUVmax values were noted between the 9 s/bed and 90 s/bed acquisitions. Conclusions: Faster whole-body PET image acquisition for patients with symptomatic bony disease remains an unmet clinical need. This feasibility trial demonstrates that digital photon counting dPET detector technology enables 10x faster Na18F PET imaging (total dPET imaging time ~ 3 min) with no loss of lesion detectability, image quality or quantitative accuracy.