Application of 18F-NaF-PET/CT in assessing age-related changes in the cervical spine of healthy adults

Introduction: Degenerative cervical spondylolysis, or cervical arthritis, is the deterioration of the cervical spine and its associated structures with increasing age. As the degenerative changes are coupled with altered osteoblastic activity, imaging modalities sensitive to such molecular changes could be valuable for clinical assessment and their precise localization. ¹⁸F-sodium fluoride (NaF)-positron emission tomography (PET) is an emerging molecular imaging modality with the potential to evaluate neck pain and degenerative changes in the spine. Specifically, dissociated ¹⁸F ions become incorporated into hydroxyapatite in actively calcifying parts of the bone and emit photons that can be captured and visualized using PET. In this study, we examined the role of ¹⁸F-NaF-PET/CT in detecting age-associated changes in the cervical spine of a healthy adult population.

Methods: We retrospectively analyzed ¹⁸F-NaF-PET/CT scans of 88 healthy volunteers (43 females and 45 males, mean age 44.6 years, range 21-75) from the Cardiovascular Molecular Calcification Assessed by 18FNaF PET/CT (CAMONA) study assigned into three age strata (20-35, 36-51, and 52-75). A semi-automated global assessment technique was used to measure ¹⁸F-NaF uptake in C1-C4 and C5-C7 vertebrae of the subjects (OsiriX software, Pixmeo, Bernex, Switzerland). Our ROI included vertebral structures such as the spinal and transverse processes, vertebral body, and lamina as well as vertebral and transverse foramina. Statistical tests and graphs were performed and plotted using GraphPad Prism 8 (San Diego, CA, USA).

Results: In both females and males, the oldest age group exhibited the greatest difference in ¹⁸F-NaF uptake between C1-C4 and C5-C7 segments (females: 3.80 ± 0.74 and 4.86 ± 0.79; p = 0.007 and males: 3.30 ± 0.79 and 4.35 ± 0.95; p = 0.02), while no such difference was observed for the youngest group. Furthermore, there was a positive linear correlation with age and cervical 18F-NaF uptake in both C1-C4 and C5-C7 vertebrae in females (C1-C4: p = 0.02, r = 0.37; C5-C7: p = 0.002, r = 0.47) and males (C1-C4: p = 0.03, r = 0.33; C5-C7: p = 0.0003, r = 0.52). Overall, females had greater 18F-NaF uptake than males in both C1-C4 (females: 3.53 ± 0.78, males: 3.07 ± 0.89, p = 0.002) and C5-C7 vertebrae (females: 4.48 ± 0.96, males: 3.91 ± 1.00, p = 0.004).

Conclusions: We found significantly greater ¹⁸F-NaF uptake in the C5-C7 than the C1-C4 vertebrae in the 52-75 (oldest) age group but not in 20-35 (youngest) age group, suggesting that the most weight-bearing parts of the cervical spine exhibit greater ¹⁸F-NaF accumulation indicative of age-related degenerative changes. High ¹⁸F-NaF uptake may correspond to increased osteoblastic activity within osteoarthritic lesions such as that seen in osteophyte formation. NaF-PET/CT may be a suitable modality to detect arthropathic lesions associated with greater osteoblastic activity and to investigate whether symptomatic lesions have high NaF avidity, which show a decrease due to therapeutic interventions.