Is positron emission tomography/magnetic resonance imaging a reliable tool for detecting vascular activity in treated childhood-onset Takayasu's arteritis? A multicentre study

Objectives: Toassess whether 18F-fluordeoxiglucose (18F-FDG) PET/MRI) with angiographic sequences can contribute to detecting vessel wall inflammation in patients with childhood-onset Takayasu's arteritis (c-TA) under immunosuppressive therapy.

Methods: A three-centre cross-sectional study was conducted. 18F-FDG PET/MRI scans were performed in c-TA patients and in oncologic patients, who served as the control group. Clinical and laboratory characteristics were also analysed.

Results: Seventeen c-TA patients (65% females) between the ages of 6 and 21 years with a mean disease duration of 9.4 years were recruited. Only one patient presented clinical disease activity and six (35.6%) had increased ESR and/or CRP levels. The most frequent magnetic resonance angiography (MRA) findings were stenosis and thickening, observed in 82.4 and 70.6% of c-TA patients, respectively. 18F-FDG PET revealed 18F-FDG uptake greater than the liver in at least one arterial segment in 15 (88.2%) patients in a qualitative analysis and a median maximum standardized uptake value (SUVmax) of 3.22 (interquartile range 2.76-3.69) in a semi-quantitative analysis. c-TA patients presented significantly higher SUVmax values than oncologic patients (P < 0.001). A positive correlation between SUVmax and CRP levels (ρ = 0.528, P = 0.029) was seen.

Conclusion: A state-of-the-art imaging modality was used in c-TA patients and revealed a strong arterial FDG uptake even in patients in apparent remission. We suppose that this finding may represent silent activity in the vessel wall; however, we cannot exclude the possibility of arterial remodelling. Importantly, a negative imaging scan may help in immunosuppression withdrawal in daily clinical practice.