The Role of 18F-FDG PET in the Diagnosis of Aortitis and Large Vessel Vasculitis

Background: 18F-FDG PET metabolic imaging provides significant help in the early diagnosis of inflammation of large and medium arteries, even before the appearance of structural vascular alterations. This retrospective study aims to evaluate the role of 18F-FDG PET in the diagnosis and management of large vessel vasculitis (LVV), including aortitis. Methodology: Fifty patients with clinical and/or biological suspicion of large vessel vasculitis but without a definitive diagnosis underwent 18F-FDG PET scanning. A qualitative visual scoring system and an average total vascular score (TVS) were used to compare 18F-FDG uptake in the vascular walls with that in the liver. Patients who had been on corticosteroids for more than 8 days were excluded from the study. Results: The study included 50 patients, 27 women and 23 men, with an average age of 65.8 ± 14.5 years. The analysis of 18F-FDG PET images allowed for the classification of subjects into two distinct groups. Among the 50 subjects, 16 (32%) showed higher 18F-FDG uptake in the vascular walls compared to hepatic uptake (PET-positive group), while 34 (68%) showed lower uptake (PET-negative group). In the positive group, 75% were diagnosed with Horton’s disease, and the remaining 25% with other inflammatory diseases such as Takayasu arteritis or polyarteritis nodosa. None of the subjects in the positive group had an aortic aneurysm. All patients with a positive 18F-FDG PET had elevated levels of C-reactive protein. The TVS obtained for aortitis alone was 5.9 ± 4.7, while the score for more global vasculitis was obviously higher, at 10.4 ± 6.3. Conclusion: 18F-FDG PET has become a valuable tool in the diagnosis of large vessel vasculitis, particularly in the early stages of the disease. It also allows for mapping of arterial involvement and estimation of disease severity using the TVS.