Background The observation that 2-deoxy-2[18F]fluoro-D-glucose-positron emission tomography/magnetic resonance imaging ([18F]F-FDG-PET/MRI) revealed high-grade arterial wall FDG uptake, without arterial wall thickening with contrast-enhancement, in a considerable number of c-TA patients in our previous study, encouraged us to compare patients with both PET and MR angiography (MRA) positives, with those with PET positive but MRA negative. Our aim was to evaluate the relevance of these two imaging modalities together. Methods A three-center cross-sectional study with 17 patients who fulfilled the EULAR/PRINTO/PReS criteria for c-TA and who underwent [18F]F-FDG-PET/MRI was previously performed. Herein we compared patients/vessels with positive PET (arterial wall 18F-FDG uptake higher than liver) and positive MRA (arterial wall thickening with contrast-enhancement)—group 1, with those with positive PET but negative MRA—group 2. Results Median disease duration of 17 c-TA patients was 10.4 years. Nine patients were classified as group 1 and six as group 2. Median of metabolic inflammatory volume (MIV) of all arterial segments was significantly higher in group 1 (2346 vs. 1177 cm3; p = 0.036). Fifty-four (19%) from 284 available arterial segments presented positive findings in vessel wall in one or both images. Positive findings were concordant between PET and MRA in only 13% arterial segments (group 1); most changes (28–59.6%) that were discordant between both images, were positive in PET and negative in MRA (group 2). Conclusion Our study demonstrated that [18F]F-FDG-PET/MRI added information about inflammation in vessel wall of c-TA patients. Prospective multicenter studies are needed in order to get solid data to guide immunosuppressive tapering and withdrawal.

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Objectives To assess whether 18F-fluordeoxiglucose-positron emission tomography/magnetic resonance imaging (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 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 laboratorial characteristics were also analysed. Results Seventeen c-TA patients (65% females) between the ages of 6 and 21 years, mean disease duration of 9.4 years were recruited. Only one patient presented clinical disease activity, and six (35.6%) had increased erythrocyte sedimentation rate (ESR) and/or C-reactive protein (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 higher than the liver in at least one arterial segment in 15 (88.2%) patients in a qualitative analysis and median standardized uptake value (SUVmax) of 3.22 (2.76-3.69) in a semi-quantitative analysis. c-TA patients presented significantly higher SUVmax than oncologic patients (p < 0.001). A positive correlation between SUVmax and CRP levels (Rho=0.528; p=0.029) was evidenced. 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 a 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.

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BACKGROUNDChildhood-onset Takayasu's arteritis (c-TA) is a rare, chronic and relapsing large-vessel vasculitis. There are few validated tools to access c-TA, so, an accurate assessment of arterial wall is mandatory to detect active inflammation and help to guide the immunosuppressive therapy. Hybrid imaging that provides anatomic and metabolic images simultaneously may add data about vascular inflammation. Our aim was to compare patients with both positive PET and MRA versus patients with positive PET and negative MRA, likewise, to compare each arterial segment with both positive PET and MRA versus positive PET and negative MRA.