18F-Sodium fluoride positron emission tomography: History, technical feasibility, mechanism of action, normal bio-distribution, and diagnostic performance in bone metastasis detection compared to other imaging modalities

The skeleton is the third most common site for metastasis overall, after the lungs and liver. Accurate diagnosis of osseous metastasis is critical for initial staging, treatment planning, restaging, treatment monitoring, and survival prediction. Currently, (99m)Tc-methylene diphosphonate whole-body scanning is the cornerstone of imaging to detect osseous metastasis. Although (18)F-sodium fluoride ((18)F-NaF) was one of the oldest medical tracers for this purpose, it was replaced by other tracers because of their better physical properties, until recently. Continued development of PET scanners has opened a new era for (18)F-NaF, and given its higher sensitivity, there have been increasing applications in imaging. In this review, we will discuss the history, technical aspects, radiobiology, and biodistribution of this tracer. Finally, we compare the accuracy of (18)F-NaF PET with other conventional imaging methods for detection of osseous metastasis.