Quantitative Assessment of the Apparent Diffusion Coefficient Values of the Inflammatory Connective Tissue Around the Mandibular Condyle in Rheumatoid Arthritis

Purpose: Magnetic resonance imaging can detect soft- and hard-tissue abnormalities and has become the primary imaging modality for temporomandibular joints. However, few studies have quantitatively evaluated rheumatoid arthritis (RA) in temporomandibular joints using diffusion-weighted imaging. The purpose of this study was to assess the apparent diffusion coefficient (ADC) values of the inflammatory connective tissue around the mandibular condyle in RA. Methods: This was a retrospective cohort study. We analyzed the magnetic resonance imaging studies of patients with suspected temporomandibular joint disorders performed between April 2008 and August 2020. The predictor variable was disease status (RA-y/n). The primary outcome variable was the mean of ADC values of the connective tissue around the mandibular condyle. The other variables were age and sex. Furthermore, the ADC values were compared between the 2 groups. Data were analyzed using a Mann-Whitney U test, Spearman's correlation coefficient, and a receiver operating characteristic curve. P <.05 was considered to indicate statistical significance. Results: In total, 35 patients (18 normal patients and 17 patients with RA) were included. The mean ADC values were 1.26 ± 0.11 × 10⁻³ mm²/s and 1.60 ± 0.19 × 10⁻³ mm²/s in the control and RA groups, respectively (P <.001). Receiver operating characteristic analysis revealed that a cutoff of 1.37 for ADC values for RA provided an accuracy of 0.86. The sensitivity and specificity of ADC values were 0.94 and 0.83, respectively. Conclusions: ADC values of the inflammatory connective tissue around the mandibular condyle in RA were significantly higher in the RA group than those in the control group. This parameter might be useful for the quantitative evaluation of RA.