Comparison of apparent diffusion coefficient in spondylarthritis axial active inflammatory lesions and type 1 modic changes

Objective The goal of this study was to evaluate whether the values of ADC in spondylarthritis axial active inflammatory lesions are different from ADC values in type 1 Modic changes. Subjects and methods 95 patients with recent lumbar pain, including 46 patients with diagnosed or suspected spondylarthritis and 49 patients with purely degenerative history, underwent spine MRI. T1w, STIR, and diffusion-weighted images (DWI) were obtained. Two musculoskeletal radiologists interpreted the images. Axial active inflammatory lesions from the SpA group and type 1 Modic changes from the degenerative group were identified on T1w and STIR sequences. ADC values from these lesions and from healthy subchondral bone were compared. Results All axial active inflammatory lesions (n = 27) and type 1 Modic changes (n = 22) identified in T1w and STIR images were visible on DWI. ADC values were significantly higher (p <0.05) for axial active inflammatory lesions (median = 0.788 × 10^-3 mm ²/s, IQR 25-75 [0.7 × 10^-3 mm²/s; 0.9 × 10^-3 mm²/s]) than for type 1 Modic changes (median = 0.585 × 10^-3 mm²/s, IQR 25-75 [0.55 × 10^-3 mm²/s; 0.60 × 10^-3 mm ²/s]) and normal subchondral bone (median = 0.443 × 10 ^-3 mm²/s, IQR 25-75 [0.40 × 10^-3 mm ²/s; 0.50 × 10^-3 mm²/s]). Intra-class correlation coefficients for intra- and inter-reader ADC values comparison were excellent (0.89 and 0.98 respectively). Conclusion DWI is a sensitive and fast sequence that offer the possibility of quantifying diffusion coefficients of the lesions, which could help to discriminate between spondylarthritis axial active inflammatory and type 1 Modic changes.