Intra-individual comparison of malignant and non-malignant osteoblastic lesions detected with an ultra-fast Na18F digital PET/CT protocol: A Phase 1 study

1693 Objectives: Sodium fluoride-18 (Na18F) PET/CT is used clinically for routine oncologic and non-oncologic bone imaging evaluation in order to detect, assess and characterize osteoblastic lesions. In those patients with symptomatic osseous lesions, new approaches are needed to substantially reduce whole-body Na18F PET image acquisition times (usually 60-120 s/bed). The recent introduction of next-generation PET/CT systems equipped with digital photon counting PET (dPET) detector technology enables faster PET image acquisition as well as PET imaging at lower administered radiotracer doses. The objective is assess the clinical potential of a 10x faster Na18F dPET imaging approach for whole-body assessment and characterization of malignant and non-malignant osteoblastic lesion and compare to standard PET image acquisition times. Methods: In this intra-individual comparison trial, investigational whole-body Na18F dPET/CT imaging (Vereos, Philips Healthcare) was performed in 50 oncologic patients using a target Na18F dose of 185 MBq. At 80 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 ~85 min post injection. Standard definition dPET image data sets (voxel volume = 4x4x4 mm3) were reconstructed using Time-of-Flight for each acquisition and then evaluated by matched pair comparison for overall image quality, background quality and lesion detectability by a blinded reader panel using an Intellispace Portal workstation. Results: All 100 data sets were rated as evaluable for qualitative assessment of 18F biodistribution and osteoblastic lesions. When compared to standard 90 s/bed acquisitions, the faster 9 s/bed dPET acquisitions demonstrated visually comparable 18F-avidity in both normal bone and osteoblastic lesions. A total of 213 discrete Na18F-avid foci were detected on the 9 s/bed and 90 s/bed acquisitions with no discordant osteoblastic lesions identified. A total of 47 foci were characterized as malignant and the remaining 166 as non-malignant. All 50 patients demonstrated non-malignant foci with the majority reflecting degenerative change but only 17 patients demonstrated malignant lesions. Quantitatively, there was no significant difference in SUVmax values for all 213 lesions on the 9 s/bed (20 ± 15) and 90 s/bed (23 ± 16) acquisitions regardless of lesion type. For 9 s/bed acquisitions, there was no difference in SUVmax between non-malignant (20 ± 13) and malignant (20 ± 20) lesions, and likewise for 90 s/bed acquisitions, there was no difference between non-malignant (23 ± 14) and malignant (24 ± 24) lesions [ANOVA, p>0.19]. There was excellent linear correlation (R2 = 0.97) between the SUVmax values for all 213 NaF-avid foci between the 9 and 90 s/bed acquisitions. Conclusions: Ultra-fast digital PET/CT imaging with a 9 s/bed acquisition using 185 MBq of Na18F is clinically feasible for the whole-body assessment of malignant and non-malignant lesions as well as qualitatively and quantitatively comparable to more traditional PET acquisition times (e.g., 90 sec/bed). Research Support: Ohio Third Frontier (TECH 09-028, TECH 10-012, TECH 13-060).