PET imaging in vasculitis

Positron emission tomography combined with computed tomography using 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG-PET/CT) is an established tool in oncology. During the past decade, this functional imaging modality that is based on increased glucose metabolism in inflammatory target cells, has become the reference standard for non-invasive visualization and monitoring of a variety of inflammatory disorders including large vessel vasculitis. Imaging plays an increasing role to confirm a suspected diagnosis of large vessel vasculitis and given the widespread implementation in daily clinical practice, standardization is of utmost importance to ensure consistency in image quality and interpretation. This article provides first, a general introduction on the clinical presentation and challenges in the diagnostic work-up of large vessel vasculitis with a focus on the two major subtypes, giant cell arteritis and Takayasu's arteritis. Secondly, practice points to perform and interpret the results of [18F]FDG-PET/CT are described in line with the recently published procedural recommendations. Furthermore, the diagnostic performance and prognostic value as well as its role for treatment monitoring are discussed taking into account the recent international recommendations for the use of imaging in large vessel vasculitis in clinical practice. Lastly, several unresolved issues and topics for future research are highlighted before concluding this article with key messages providing an up to date guidance for the role of [18F]FDG-PET/CT in patients with suspected large vessel vasculitis.