Giant cell arteritis (GCA) is the most common vasculitis in adults. The diagnosis of GCA is evoked by the association of clinical signs and biological anomalies (inflammatory syndrome) in patients over 50 years of age. On the other hand, starting a treatment implies being certain of the diagnosis which requires performing a temporal artery biopsy under local anesthesia. This examination is therefore an invasive procedure for patients whose sensitivity is not optimal. This is why imaging techniques (echo-Doppler or MRI of the temporal arteries) have been developed to look for signs of vasculitis without the need to perform a biopsy. However, these examinations lack sensitivity (=falsely concluding the absence of GCA) and specificity (=falsely concluding the presence of GCA). Recently, advances in imaging, and in particular positron emission tomography (PET), have made it possible to visualize the cephalic arteries, including the temporal artery.

The aim of this study is therefore to evaluate the sensitivity and specificity of PET of the cephalic arteries for the diagnosis of GCA and to compare them with those of echo-Doppler and MRI of the temporal arteries.

Inclusion Criteria:

• Any patient for which the diagnosis of GCA is suspected and who underwent a cervical PET/CT

Exclusion Criteria:

• previously diagnosed GCA, glycemia > 7 mmol/L, PET CT performed more than 72 h after introduction of glucocorticoids, age < 50 years

outpatient