The Role 18F-FDG and 18F-NaF PET/CT in Assessment of Temporomandibular Joint Metabolic Activity in Rheumatoid Arthritis
Positron emission tomography
Objective: The aim of this study was to evaluate the efficacy of 18F-fluorodeoxyglucose (FDG) and 18F-sodium fluoride (NaF)PET/CT for assessing the status of the temporomandibular joint (TMJ) of rheumatoid arthritis (RA) patients compared with healthy (non-RA) individuals. Method: Eighteen patients diagnosed with RA (mean age 55±12.1years: 4 females and 14 males) were included in the test group. Eighteen age-, sex- and race-matched healthy control subjects were selected from the CAMONA clinical trial. PET/CT images were acquired 180-minute post-intravenous administration of FDG and NaF (2.2 MBq/kg). For FDG analysis, regions of interest (ROIs) were manually assigned per anatomical boundaries using a closed polygon tool. The first ROI of the mask was assigned on the trans-axial CT slice with the first evidence of the glenoid fossa down to two to three slices inferiorly. The ROI followed the anatomy of the TMJ. For NaF, a three-dimensional ball tool of 1.5 cm was used to assign ROIs with the head of the mandibular condyle located at the center including the osseous compartment of the joint extending inferiorly to the neck of the condyle. Averaged SUVmean was used to semi-quantify FDG and NaF uptake in each joint. Then average SUVmean of the right and the left TMJ was determined. For normalization, a Target to Background Ratio (TBR) was used. For statistical analysis, the student’s t-test and regression analysis were used. The severity of RA was assessed by determining the Disease Activity Score of serum C reactive protein (DAS-28 CRP) and erythrocyte sedimentation rate (DAS-28 ESR) for each subject. Results: FDG TBRmean for the test group was 1.21±0.33 compared to 0.91±0.2 in controls, (p=0.003.) No correlation was found between FDG uptake and DAS28-CRP or DAS28-ESR. The NaF average SUVmean was significantly higher in RA patients than healthy control subjects (2.4±0.8 versus 1.9±0.4, p=0.02). Similarly, the TMJ TBRmean was also higher in RA patients relative to healthy controls (4.2±2.1 versus 2.7±0.9, p=0.01) A significant positive correlation was found between TBRmean and DAS28-CRP (r=0.49, p=0.03), while there was positive trend in the correlation between TBRmean with DAS28-ESR that was not statistically significance (r=0.37, p=0.12). Conclusion: RA patients appear to have significantly higher metabolic activity in the TMJ than age-, sex- and race-matched healthy control subjects. Our results illustrate the potential value of using FDG and NaF-PET/CT for evaluation of TMJ disorders and suggest that this modality may useful for monitoring the effects of treatment regimens.