Abstract
1206
Objectives: The temporomandibular joint (TMJ) is a complex body joint that plays an important part in daily activity: chewing, speaking, swallowing. When the TMJ is involved in rheumatoid arthritis (RA) it can result in patient discomfort, crepitation, stiffness and limitation in mouth opening.According to clinical evaluation and standard imaging, the prevalence of TMJ affection in RA patients ranges from 10% to 58%. Imaging modalities used to evaluate TMJ involvement include panoramic X-ray, cone beam computed topography (CBCT)and MRI, but functional imaging using PET/CT scans of TMJ in RA patients has rarely been reported. The aim of this study was to evaluate the role of FDG-PET in evaluating the TMJ of RA patients compared with healthy, non-RA individuals.
Methods: Eighteen patients diagnosed with RA (mean age 57±12.1 , range 25-69, 4 female and 14 male) were included in this study as the test group and 18 healthy control subjects (mean age 54 ±13.1 , range 24-75) were selected from the CAMONA clinical trial with matching age and gender. PET/CT images were acquired 180-minute post intravenous administration of FDG. OsirX® MD v.9.0 software (Pixmeo SARL, Bernex, Switzerland) was used for image 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 transaxial CT slice with the first evidence of the glenoid fossa up to 2-3 slices inferiorly. The ROI followed the anatomy of TMJ where it bounded anteriorly by the articular eminence of the temporal bone, posteriorly by the tympanic portion of the temporal bone, medially by the sphenoid bone and laterally by the root of zygomatic process of the temporal bone (Figure 1 a & b). FDG uptake was then measured in the joint as Average SUVmean. The SUVmean was calculated based on the following equations: TMJ metabolism= ∑ (Silce SUVmean [asterisk] slice ROI volume). Average SUVmean= (TMJ metabolism/ ROI total-volume).For normalization, the Target to Background Ratio (TBR) was calculated for each subject by dividing average TMJ SUVmean by SUVmean uptake in the superior vena cava. For statistical analysis student’s t-test was used to compare TBRmean in RA and control subjects.
Results: The average SUVmean of RA patients was 1.18± 0.47 compared to 1.09± 0.27 in healthy controls, p=0.48. TBRmean for test group was 1.21±0.33 compared to 0.91±0.2 in controls, with statistically significant difference, p=0.003.
Conclusions: RA patients appear to have significantly higher metabolic activity in the TMJ than age/ gender matched healthy control subjects. Our results illustrate the potential value of using FDG-PET/CT for evaluation of TMJ disorders and suggest that this modality may be applied for monitoring effects of treatment regimens.
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