18F-sodium fluoride PET-CT hybrid imaging of the lumbar facet joints: Tracer uptake and degree of correlation to CT-graded arthropathy

Abstract

We aim to evaluate 18F-NaF uptake by facet joints with hybrid PET-CT technique. Specifically, we evaluate NaF uptake in the facet joints of the lower lumbar spine, and correlate with the morphologic grade of facet arthropathy on CT. 30 consecutive patients who underwent standard vertex to toes NaF PET-CT for re-staging of primary neoplastic disease without measurable or documented bony metastases were identified. Maximum (SUVmax) and average (SUVavg) standardized uptake values were calculated for each L3-4, L4-5, and L5-S1 facet joint (n = 180) and normalized to average uptake in the non-diseased femur. A Pathria grade (0-3) was assigned to each facet based upon the CT morphology. Spearman's rank correlation was performed for normalized SUVmax and SUVavg with Pathria grade. ANOVA was performed with Tukey-Kramer pairwise tests to evaluate differences in uptake between Pathria groups. Facet normalized SUVmax (r = 0.31, P < 0.001) and SUVavg (r = 0.28, P < 0.001) demonstrated a mild positive correlation with CT Pathria grade. There was a wide range of uptake values within each Pathria grade subgroup with statistically significant differences in uptake only between Pathria grade 3 as compared to grades 0, 1, and 2. In conclusion, NaF uptake and morphologic changes of the facet joint on CT are weakly correlated. Physiologic information provided by NaF uptake is often discrepant with structural findings on CT suggesting NaF PET may supplement conventional structural imaging for identification of pain generating facet joints. Prospective investigation into the relationship of facet joint NaF uptake with pain and response to pain interventions is warranted.

[18F]-Sodium Fluoride PET MR–Based Localization and Quantification of Bone Turnover as a Biomarker for Facet Joint–Induced Disability

“…This finding is consistent with a previous study wherein a similarly weak correlation was found between NaF-PET uptake and CT measures of facet arthropathy, further supporting the hypothesis that physiologic information afforded by NaF uptake may supplement conventional structural imaging for identifying symptomatic facet joints. 6 …”

“…3–5 The utility of 18 F-NaF PET for evaluating degenerative disease of the lumbar spine remains largely unexplored. 6 …”

Novel Musculoskeletal and Orthopedic Applications of 18F-Sodium Fluoride PET

“…Not only does NaF-PET/CT facilitate the diagnosis of pars stress but it can also help diagnose other potential causes of back pain, such as facet arthropathy. [80][81][82] The observation that NaF uptake at the cervical, thoracic, and lumbar spine is associated with increased body weight in healthy individuals suggests that NaF-PET/CT can detect early changes in the spine related to degeneration. 83 In 42 adult patients with back pain and no history of spine surgery, NaF-PET/CT scans identified the cause of pain in 37 (88%) of the patients.…”

“…82 Furthermore, NaF activity at lumbar facet joints has been found to correlate with both MR findings and clinical disability. 80 Mabray and colleagues 81 observed that, in 30 adult patients who underwent imaging by NaF-PET/CT, uptake of NaF was only weakly correlated with CT Pathria grade of facet osteoarthropathy. Thereby, the investigators reasoned that the assessment of bone turnover with NaF provided new information that can be used to supplement structural data provided by CT.…”

Identifying Musculoskeletal Pain Generators Using Clinical PET

“…36,40 Additionally, increased F 18 -NaF uptake was shown to correlate well with those patients with facet joint pain. [41][42][43] Further, significantly increased F 18 -NaF PET subchondral bone uptake was observed in a patient population at risk for developing degenerative joint disease. 44 These findings support the hypothesis that increased metabolic bone activity detected with F 18 -NaF PET can serve as a marker for early bone remodeling in OA.…”