Giant cell arteritis (GCA or temporal arteritis or cranial arteritis) or Horton disease is a vasculitis that occurs in older adults, affecting vessels of medium and large caliber. The diagnosis of GCA is a challenge for general practitioners and specialists. Since 1970, it is based on a combination of clinical, biological and histological signs. Temporal artery biopsy (TAB) was the reference method until recently. However, TAB has many drawbacks. Therefore, researches of the past 20 years have been intended to develop alternative diagnostic methods. This was notably the case of the color Doppler ultrasound (CDU) since the description by Wolfgang Schmidt of the halo sign. Although European and British recommendations put CDU as second line method, many authors suggest the possibility to do without TAB in many cases. In addition, many practitioners believe that it is not "ethical" to use an invasive unprofitable procedure like TAB, and have already been using CDU in their routine practice. However, no diagnostic algorithm validating this approach in a prospective series has been published to date. Therefore, the present study aim at validating a diagnostic algorithm of giant cell arteritis using color Doppler imaging of temporal arteries and cervicocephalic axes as first screening method.