Total-Body NaF-PET/CT and its Implications for Osteoporosis

Objectives: 1. Review imaging modalities currently available for osteoporosis diagnosis and management 2. Discuss the potential role of NaF PET/CT in early detection of osteoporosis 3. Highlight the revolutionary effect total-body PET/CT can have with regards to osteoporosis Methods: Osteoporosis is a process by which osteoblastic activity (new bone formation) does not keep up with osteoclastic activity (bone degradation). As such, bone density and quality progressively weakens. Currently, the predominant clinical imaging modality used for diagnosis and management of osteoporosis remains dual-energy X-ray absorptiometry (DXA). DXA measures bone mineral density (BMD) and quantifies it on a T-score scale in which normal bone density and osteoporosis lie on opposite ends. 18F-sodium fluoride positron emission tomography/ computed tomography (NaF-PET/CT) is a molecular imaging modality, albeit one that quantifies osteoblastic activity rather than bone density. Since the dip in osteoblastic activity precedes the eventual decrease in bone density, it remains of interest to see if NaF-PET/CT can lead to earlier detection of weakening bone when compared to DXA. Thus, the focus of this exhibit shall be to review the application of NaF-PET/CT to different skeletal sites, and how the invention of total-body PET/CT scanners could revolutionize this application. Results: In recent years, a number of studies have successfully quantified osteoporosis in the lumbar spine, hip, tibia, femur etc. in both human subjects and animals using NaF PET/CT. Currently, the most used form of PET/CT imaging remain whole-body scanning; this name is a misnomer though, as it typically only scans from the top of the head down to the mid-thigh region with an axial field of view of approximately 12-26 cm/bed. Osteoporosis however, can affect even the foot and ankle region and furthermore, an entire skeletal study could provide information of biodistribution and a better understanding of the osteoporosis process. With this in mind, a novel total-body PET/CT scanner named EXPLORER which scans the entire body simultaneously, can be used to measure all possible osteoporotic bones in a subject. Furthermore, total-body PET/CT possesses numerous other benefits over whole-body PET/CT, such as reduced injection dosage by a factor of 40, quicker scan times, higher sensitivity, full total-body kinetics etc. Therefore, total-body PET/CT is an extremely promising technique that can make diagnosis and management of osteoporosis using NaF dramatically more refined and accurate. Conclusions: As NaF PET/CT becomes more popular in evaluating skeletal calcium metabolism (as shown by the measurement of osteoporosis), advancing technology such as total-body PET/CT scanners should be used to take complete advantage of this imaging modality. We believe that future, well-powered studies are needed to prove this prediction, and detail the far-reaching benefits today-body PET/CT scanners can have for osteoporotic patients.