MRI and Ultrasound in giant cell arteritis: complementary strengths and combined diagnostic value.

Imaging is central to the diagnosis of giant cell arteritis (GCA). However, direct comparisons between magnetic resonance imaging (MRI) and ultrasound remain limited, particularly regarding vascular involvement patterns and their combined diagnostic value. This study compared MRI and ultrasound in suspected GCA and evaluated whether their combination improves diagnostic accuracy. We retrospectively analyzed 183 patients with suspected GCA evaluated at a tertiary care center between July 2017 and October 2022. MRI was performed in all patients using a graded sum score across multiple cranial and extracranial vessel territories. Ultrasound was performed in 159 patients (87 %) using a binary sum score assessing temporal, common carotid, and subclavian/axillary arteries. Vessel inflammation patterns were characterized across both modalities, and diagnostic performance was assessed using receiver operating characteristic curve analysis. GCA was diagnosed in 101 patients (55 %). Bilateral vessel involvement distinguished GCA from non-GCA and extended beyond subclavian/axillary arteries to include temporal, occipital, and vertebral territories. MRI achieved strong diagnostic accuracy (AUC 0.90; sensitivity 0.88; specificity 0.85), as did ultrasound (AUC 0.89; sensitivity 0.84; specificity 0.92). Cross-modality correlations were strongest for temporal arteries (r = 0.52). When MRI and ultrasound findings were concordant (82 % of cases), diagnostic performance improved further (AUC 0.94; sensitivity 0.96; specificity 0.92). MRI and ultrasound each provide high diagnostic accuracy for GCA while capturing complementary patterns of vascular inflammation. Bilateral involvement across multiple vascular territories is a defining disease feature. Concordant multimodal imaging substantially enhances diagnostic confidence and supports a combined imaging approach in patients with suspected GCA.