[18F] FDG-PET/CT as a new and sensitive imaging method for the diagnosis of large-vessel vasculitis

To determine the value of the new imaging modality positron-emission tomography/computed tomography (PET/CT) for the diagnosis and re-evaluation of large vessel vasculitis. Thirteen patients newly diagnosed or re-evaluated for suspected clinical disease activity of Takayasu arteritis (TA, 3 patients) or giant cell arteritis (GCA, 10 patients) underwent PET/CT. Clinical activity status, serological markers, and alternative imaging methods were evaluated. In patients with clinical activity despite nearly normal erythrocyte sedimentation rate (ESR) and C reactive protein (CRP), disease activity could be shown by PET-CT. A long segmental, increased fluoro-deoxyglucose (FDG) uptake in the vessel wall served as confirmation of the vascular inflammation. The aortic arch was involved in all patients with active disease (n=12). In the complementary CT scans, stenotic lesions were found in 8 out of 13 patients. Duplex ultrasonography was performed in 11/13 patients and was positive in nine of these patients at least at one site. Magnetic resonance imaging (MRI) was done for confirmation in 10 patients. Doppler ultrasonography is a very useful and widely available method to confirm a first suspicion of vasculitis, but it has limitations especially at the large thoracic vessels, which are affected in many cases. ESR and CRP alone are not sufficient to evaluate disease activity. The new imaging modality PET/CT provides the additional information. It allows the evaluation of disease activity and vessel morphology as well as the localization of the inflammatory process in the same session.