Semiquantitative Interpretation Criteria for Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography in Large-Vessel Vasculitis: Pattern Recognition and Correlation with Polymyalgia Rheumatica

BACKGROUND: Fluorine-18-fluorodeoxyglucose ((18)F-FDG)-positron emission tomography/computed tomography (PET/CT) is emerging as a useful imaging modality in suspected large-vessel vasculitis (LVV), owing to its ability to accumulate at the sites of inflammation within the arterial walls. However, there remains scope for standardization of reporting criteria to ensure reproducibility. Recently, a semiquantitative scoring system called “total vascular score” (TVS) has been suggested as a method to standardize and harmonize FDG PET/CT evaluation in LVV patients. The purpose of this study was to assess the clinical utility of the proposed semiquantitative grading scale in LVV patients. MATERIALS AND METHODS: Patients presenting with clinical symptoms of vasculitis, who had undergone a baseline FDG-PET/CT were evaluated. (18)F-FDG uptake in the major vessels was quantified with standardized uptake values (SUVs(max)) using four-point scale by three independent nuclear physicians. TVS was calculated based on the calculation of the vascular uptake values with respect to mediastinal blood pool and liver uptake and the number of vessels involved. RESULTS: A total of 106 PET-positive patients (74 males and 32 females) were evaluated. The most frequently involved vessels were thoracic aorta >abdominal aorta >subclavian arteries with mean SUV(max) values of 4.05, 3.12, and 2.70, respectively. Mean TVS was 13.18 ± 3.4 (range 03–19) among 276 involved vessels. TVS showed significant positive correlation with erythrocyte sedimentation rate (r = 0.82; P < 0.005). 18 patients showed periarticular FDG uptake, with shoulder joint being the most commonly involved joint. CONCLUSION: The simplified visual and semiquantitative grading scale for interpretation and reporting classification provides better objectivity in diagnosis, communication with referring clinicians, and planning in patients of LVV.