Is there a role for DWI in the diagnosis of sacroiliitis based on ASAS criteria

Purpose: Sacroiliitis based on MRI is one of the main diagnostic criteria of axial spondyloarthritis (SpA). Our purpose was to assess (a) whether apparent diffusion coefficient (ADC) values on diffusion-weighted imaging (DWI) differ between regions of bone marrow edema (BME) and subchondral normal-appearing bone marrow (NABM) in active sacroiliitis, (b) whether ADC values can differentiate early SpA and chronic SpA, both in the active and inactive phase, and (c) whether ADC values are related to laboratory findings. Materials and methods: 47 patients (24 female, 23 male, mean age: 38.53 years) with the diagnosis of SpA were included in this retrospective study. 20 age- and sex-matched subjects without SpA constituted the control group. ADC measurements were taken from all lesions and NABM of each sacroiliac joint. Results: A total number of 120 subchondral BME lesions (acute: 17, chronic active: 103) were noted. The mean ADC values of the BME lesions (1.30 ± 0.18 × 10-3 mm2/s) were significantly higher than the ADC values in the NABM regions (0.55 ± 0.08 × 10-3 mm2/s) as well as in both the control group (0.56 ± 0.05 × 10-3 mm2/s) and the chronic inactive group (0.54 ± 0.03 × 10-3 mm2/s). There were more BME regions in patients with chronic active sacroiliitis than early SpA patients. Correlation was found between the CRP values and ADC values. Conclusion: DWI with ADC values may be complementary to FS T2-weighted or STIR MR images for accurately diagnosing inflammatory sacroiliitis. The value of DWI versus dynamic contrast-enhanced imaging in the follow-up needs to be clarified.