[Usefulness of imaging in large vessel vasculitis].

The imaging is essential for the diagnosis of large vessels arteritis, in order to assess the persistent inflammation of arterial lesions, to evaluate the treatment response and search the vascular complications. In patients with giant cell arteritis (GCA), the aortitis could be suspected in 2 situations: in the presence of general constitutional symptoms or systematic screening of aortitis in patient with confirmed GCA. The frequency of aortitis varies according to the imaging method and could be detected in 40 % of patients with computed tomography and MRI, and approximately in 60 % with FDG-PET/CT. The clinical and prognostic value of systematic detection of aortitis during the GCA remains to be determined. In Takayasu arteritis, imaging is performed to diagnose the large vessels vasculitis, to determine the arterial lesions extension to assess the persistent inflammation of arterial lesions. The persistent vascular inflammation should be suspected in the presence of arterial thickness, of arterial enhancement, a parietal edema and increased arterial FDG uptake (>liver). However, the value of these parameters and the threshold remain to be determined. Thus, the value of FDG-PET/CT and MRI and of parameters used to characterize the persistent arterial inflammation should be further studied.