Background In the diagnosis of giant cell arteritis (GCA) with aortic involvement, fluorine-18-fluorodeoxyglucose positron emission tomography / computed tomography hybrid imaging ([18F]-FDG-PET/CT) has been demonstrated to be a powerful tool. Its predominant application comprises extracranial involvement, and temporal arteries are typically below detectable levels of PET scanners, which repeatedly showed to be limiting in finding increased [18F]-FDG accumulation even in histologically proven cases. Study was performed to verify if high FDG uptake in the walls of large vessels is corresponding with giant cell arteritis.
Methods 39 patients with suspicion of large-vessel vasculitis formed a cohort (30 males and 9 females). Levels of ESR and CRP were evaluated and correlated to FDG uptake - based on PET (25 pts) and PET/CT (14 pts) imagines. FDG uptake was measured in 7 vessel areas with an area evaluated as positive when it surpassed an uptake of the liver parenchyma. In all patients were performed standard scanning of the body at the extent from the proximal thirds of femurs to the cranial base. For verification of vasculitis, a direct proof using histologic examination of a temporal arteria was performed (4 pts), or an indirect one – a therapeutic test for ESR and CRP decreases during corticosteroids therapy (39 pts) were used.
Results The mean age and median of patients with suspition of vasculitis was 64.9, respectively 65 years. In all patients standard scanning of the body showed high [18F]-FDG uptake in the great arteries and their branches. This finding was compatible with active giant cell arteritis (maximum intensity projections, whole body protocol, Grey scale).
Giant cell arteritis was proved in 3 from 4 histological examinations. By indirect testing, vasculitis in all 39 patients was confirmed by using decreased inflammatory parameters. Mean ESR before starting corticosteroid were 110 mm/hr (72-150 mm/hr), respective 100,5 mg/l (41-232 mg/l) for CRP. Control laboratory results after starting corticosteroids (mean 139 days) were decreased to mean 30 mm/hr (9-40) (p<0.0001), respective 5,8 mg/l (0,6-35,8 mg/l) (p<0.0001). In one patients with definitive diagnosis of giant cell arteritis based on histopathological examination of an excised parietal branch of the left temporal artery scanning the brain (PET/CT brain protocol, axial slices, low dose CT, PET Spectrum scale) was performed. [18F]-FDG hypermetabolism was also detected in both temporal arteries, in their frontal and parietal branches as well as in both occipital arteries.
Conclusions The finding of generalized high FDG uptake in large vessels in patients with symptoms of active inflammatory disease gave evidence for large vessel vasculitis. The PET (PET/CT) examinations detected the disease in its early phase and also can determined the extent. Direct imaging of afflicted temporal vessels was successful only by using a hybrid PET/CT scanner. To the best of our knowledge this is the first demonstration of increased [18F]-FDG uptake direct in temporal and occipital arteries and even in smaller branches.
Disclosure of Interest None Declared