Fully integrated [18F]FDG PET/MR in large vessel vasculitis.

Abstract

The aim of this study is to evaluate the usefulness of [18F] fluorodeoxyglucose (FDG) positron emission tomography (PET)/magnetic resonance (MR) in large vessels vasculitis (LVV) patients. We performed an observational retrospective study based on our records. Images were acquired on a PET/MR scanner using [18F]FDG-PET whole body imaging. For each PET scan, a qualitative analysis and a semi-quantitative measure using the maximum of the standardized uptake value (SUV<inf>max</inf>) were performed. SUV<inf>max</inf> measurements normalized to the liver uptake were categorized using a grading scale. Vessel's wall thickness (WT) was measured at five fixed points (inferior margin of T5, T9, T12, L3, thickest area [max WT]). Twenty-three LVV patients were included, 56.5% giant cells arteritis, 34.8% Takayasu's arteritis and 8.7% isolated aortitis, all Caucasian, mostly females (82%). We considered 32 PET scans for the LVV group (from a minimum of one to a maximum of three scans per patient) mainly during follow-up (29/32 scans), and 23 PET scans from a control group of non-metastatic malignancies patients. We found higher SUV<inf>max</inf> compared to controls, in all sites, irrespective of clinical disease activity. Mean WT resulted higher in patients than in controls but was not correlated to SUV<inf>max</inf>. Mean WT positively correlated with age in both cohorts, inversely correlated to disease duration, while no correlation with SUV<inf>max</inf> was observed. The concordance between clinically active disease and PET hypermetabolism was poor (Cohen' κ=0.33). PET/MR is a safe imaging technique capable of detecting inflammation in aortic wall. Low radiological exposure of PET/MR should be considered especially in young women receiving follow-up studies.