Precision Bone PET imaging: Ultra-high definition image reconstruction enabled by digital PET/CT in a pre-clinical canine model

Objectives: To assess the feasibility and translational potential of ultra-high definition image reconstruction using a digital photon counting PET (dPET) in a canine model. Methods: Eight adult male beagles (weight (kg) mean ± SD; 14± 1.54) were scanned. The dogs were administered 1 mCi Na¹⁸F. Imaging started ≃ 45 min post injection for 33 min total acquisition time. Covering the whole body, 11 bed positions, acquiring 180 seconds per bed position. All imaging was performed on a digital photon counting system (Philips Vereos). PET listmode data were reconstructed using using Time-of-Flight with 64mm³ (standard definition/SD), 8mm³ (high definition/HD), and 1mm³ (ultra-high definition/UHD) voxel volumes. Point spread function, and Gaussian filtering were applied. Two experienced blinded readers evaluated image sets overall quality, tissue characterization, and quality of background in the whole body skeleton. Three-dimensional (3D) regions of interest (ROI) were traced over the distal femur, first lumbar vertebra, and a portion of the liver, recording measured SUV_max. Results: Whole body static acquisitions and reconstructions were completed successfully. Resulting in excellent image quality, specifically when using a large reconstruction matrix for 1mm voxel volumes (UHD). Qualitatively assessment provided detailed insight into skeleton uptake characteristics. Sharper images were provided by HD and UHD recons in comparison with SD recons. Image quality was consistently ranked higher in UHD images. Na¹⁸F activity in normal tissues/structures was better characterized with HD/UHD recons. Quantitative measures were highly consistent among tissue/structure ROIs in all subjects. Conclusion: High and UHD image reconstruction using a dPET demonstrated an improved visualization and characterization of Na¹⁸F activity in normal tissues/structures in the whole body/skeleton. The improved image quality and tissue characterization appears to be enabled by higher definition reconstruction reducing partial volume. Next-generation digital PET technology in addition to HD and UHD post-processing showed feasibility to develop new imaging protocols, such as ultra-fast or ultra-low dose imaging. Making use of high definition post-processing protocols appeared readily feasible and robust in this animal model and in clinical studies performed by our group. Such recons are useful to evaluate pet patients as well as research animals that are smaller than human patients, and thus, need improved image quality for a precise diagnosis. Further studies can be performed with other radiotracers. Our Na¹⁸F canine nuclear imaging model may advance PET innovations and open new opportunities in translational imaging.