Imaging in large-vessel vasculitis.

Imaging has recently been acknowledged as at least equivalent to histology for confirming large-vessel vasculitis in the recommendations of scientific societies. Many studies have been recently published on the use of ultrasound, magnetic resonance imaging (MRI), computed tomography (CT) and fluorodeoxyglucose (FDG) positron emission tomography (PET) in giant cell arteritis and Takayasu arteritis. Ultrasound, MRI and CT show concentric, arterial wall thickening in vasculitis. PET demonstrates enhanced FDG uptake of inflamed artery walls due to increased glucose metabolism. Ultrasound is particularly useful for smaller arteries like the temporal arteries due to its high resolution. MRI and PET/CT provide an excellent overview particularly on extracranial arteries. However, ultrasound can also detect extracranial vasculitis while PET/CT may delineate vasculitis in temporal arteries. The diagnosis needs to be confirmed without delay as the sensitivity of imaging decreases with treatment. Ongoing studies are evaluating the role of imaging for follow-up.