AbstractIntroduction/AimsThe performance of magnetic resonance imaging (MRI) for diagnosing suspected idiopathic inflammatory myopathy (IIM) remains controversial. Furthermore, the role of contrast‐enhanced magnetic resonance imaging (CE‐MRI) sequences is unclear. The aim of this study was to evaluate the sensitivity and specificity of a non‐enhanced magnetic resonance imaging (NE‐MRI) protocol compared to a CE‐MRI protocol in adult patients with confirmed IIM.MethodsThis study retrospectively enrolled patients with suspected IIM who underwent MRI of the upper thigh between 2008 and 2020. The protocol consisted of a T1‐weighted (T1w) sequence, a turbo inversion recovery magnitude (TIRM) sequence and a contrast‐enhanced T1‐weighted sequence (CE‐T1w). After randomly stratifying patients into a group with only the T1w and TIRM sequences available and another group with additional availability of CE‐T1w, three blinded readers assessed the presence of IIM based on characteristic imaging features. Confirmation of the diagnosis was determined based on the 2017 ACR/EULAR criteria.ResultsOf the 80 patients (mean age 49.0 ± 21.1 years; 42 female, 38 male) included, 54 (67.5%) had a positive diagnosis of IIM. Cumulated sensitivity and specificity for MRI to detect IIM was 87.1% and 83.3% in the NE‐MRI group versus 87.0% and 63.0% in the CE‐MRI group. The group differences for sensitivity and specificity were non‐significant for each of the three readers, respectively (p ≥ .081).DiscussionNE‐MRI detects suspected IIM with high diagnostic accuracy and performs equivalently to CE‐MRI. Therefore, it may be appropriate to omit the use of contrast agents in MRI scans performed for suspected IIM.