Figure 1.

PET scan showing ¹⁸F-FDG-uptake in large- and medium- sized vessels. Maximum intensity projection (MIP) image of a whole-body PET-image of a 67-year-old male with high fever, mild headache, and a CRP value of 300 mg/l. After an extensive clinical workup, suspicion of vasculitis occurred, when there was no response to antibiotics. Whole-body CT showed no infection or malignant focus. Temporal arterial biopsy was equivocal. A PET/CT scan confirmed the vasculitis diagnosis by showing a tree-root-like ¹⁸F-FDG uptake pattern in large- and medium-sized arteries in the lower limbs. Physiological tracer uptake is noted in the brain, the neck muscles, the myocardium, the kidneys, and the bladder.