It has recently been reported that color Doppler ultrasonography can be used to diagnose TA. Arterial inflammation causing peri-vascular edema appearing as a "dark halo" and segmental stenosis of the temporal artery are characteristic ultrasound findings suggestive of TA. If there is no dark halo sign, a diagnosis of TA cannot be supported and temporal artery biopsy can be avoided in most of these patients. The presence of the dark halo sign has a positive predictive value of only 50%.