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PET-CT Vascular Grading — SCE Rheumatology MCQ

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HardMusculoskeletal ImagingPET-CT Vascular GradingSCE Rheumatology

A 55-year-old man is investigated for suspected large-vessel vasculitis before glucocorticoid treatment. FDG-PET/CT shows smooth circumferential uptake in the thoracic aorta and both subclavian arteries that is visually greater than hepatic uptake, without corresponding focal calcified atheroma. Using the recommended qualitative vascular-to-liver FDG uptake scale, which classification and interpretation are most accurate?

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Correct answer: A — Grade 3 — compatible with active large-vessel vasculitis when the distribution and clinical context are concordant

The vascular-to-liver visual scale grades FDG uptake as 0 (no or background-level uptake), 1 (below liver), 2 (equal to liver) and 3 (greater than liver). Uptake exceeding liver is therefore grade 3, not grade 2. A smooth circumferential pattern affecting the aorta and major branches, particularly before glucocorticoid exposure, is compatible with active large-vessel inflammation when the clinical context supports vasculitis. It is not independently diagnostic: focal or patchy uptake, especially with calcified plaque, may reflect atherosclerosis. Grade 2 is equal to liver and is less specific, so it requires cautious contextual interpretation. PETVAS is a separate composite research/activity score rather than the name of an individual vessel grade, and FDG-PET depicts metabolic inflammatory activity rather than structural damage alone.

Reference: Yin P et al. Variants of physiological FDG vascular activity on digital PET. 2024. https://pubmed.ncbi.nlm.nih.gov/39604276/