Large Vessel Vasculitis: Multimodality Imaging Findings and Technical Principles.

Vasculitides are disorders characterized by inflammation of blood vessels and are typically classified by their size. Large vessel vasculitis (LVV) is divided into two main categories of giant cell arteritis (GCA) and Takayasu arteritis (TA). Although there are key distinguishing factors in their presentation, in reality, both conditions can behave nonspecifically with generalized symptoms making diagnosis challenging. Noninvasive imaging has a role in identifying, classifying, and staging LVV; often with a multimodality approach including US, CT and MRI with angiography, and fluorine 18 (18F)-fluorodeoxyglucose (FDG) PET/CT. The choice of imaging examination may vary according to patient presentation and local protocols, but international guidance recommends US as a first-line alternative to temporal artery biopsy in diagnosing GCA and mandates extracranial imaging when initial images are negative. In TA, cross-sectional body imaging is advised, ideally with MRI with angiography, owing to the lower radiation doses and effectiveness of structural assessment. Functional imaging with 18F-FDG PET/CT and advancements in vessel wall and diffusion-weighted MRI show promise in monitoring activity and assessing treatment response but require validation. The authors describe the epidemiology, presentation, pathogenesis, and management of the primary large vessel vasculitides; outline generic and specific multimodality imaging findings alongside technical aspects; and consider the role of imaging in monitoring disease activity and treatment response. Variable vessel and secondary vasculitides, which can involve large vessels, are briefly reviewed. ©RSNA, 2025.