Performing a temporal artery biopsy is still the easiest way to diagnose giant cell arteritis. However, this biopsy is not always positive, even not in patients with prominent cranial symptoms. In these cases, positron emission tomography with 18-fluorodeoxyglucose as a tracer is a valid alternative. This nuclear technique has demonstrated that involvement of large arteries such as the aorta or the subclavian arteries occurs in 50 to 80% of patients. Ultrasonographic examination of an inflamed temporal artery can demonstrate a "halo", corresponding to edema of the intimal layer of the artery. Only in very experienced hands, this non-invasive technique can replace a surgical biopsy. Magnetic resonance imaging and computerized tomographic scanning are not used in the diagnosis of giant cell arteritis, but these techniques can visualize the extent of the disease, e.g. to the aorta with possible aortitis or to a partical artery.