Halo Sign Vanishing Time After Steroids Outbreak in GCA Patients

Inclusion Criteria: * Patients aged 50 and over * Without legal protection. * Meeting GCA classification criteria as defined by ACR 2022 with the presence of a halo sign-unilateral or bilateral-on Doppler ultrasound of the temporal artery. * Newly diagnosed with an indication for corticosteroid treatment. * Have not yet received corticosteroid treatment for GCA. * No contraindication to corticosteroid treatment. * Person affiliated with or benefiting from a social security scheme. * Free, informed and written consent signed by the participant and the investigator (at the latest on the day of inclusion and before any examination necessary for the research). Exclusion Criteria: * Patients with a relapse of Giant Cell Arteritis (GCA). * Patients who have previously undergone a temporal artery biopsy (TAB), including for other reasons. * Patients who have received oral corticosteroid treatment in the past month or are currently on corticosteroid therapy (excluding hydrocortisone or local corticosteroids). * Patients with other types of vasculitis that may constitute a differential diagnosis: presence of antibodies against the cytoplasm of neutrophils (ANCA), positive syphilis serology, positivity of an IGRA test (Interferon Gamma Release Assay). * Patients having received immunosuppressive treatment or biotherapy in the month prior to inclusion. If the patient's condition warrants the use of biotherapy or immunosuppressive treatment, its initiation will be delayed until after Day 7 to avoid interfering with the Doppler procedure.