Objective <p>Arterial wall Fluorodeoxyglucose (FDG) uptake can reflect vascular inflammation in Takayasu’s arteritis (TAK); however, its association with vascular prognosis remains unclear. This study assessed the predictive efficacy of the PET vascular activity score (PETVAS) for vascular prognosis and whether FDG uptake in specific arterial territories was associated with angiographic progression in TAK.</p> Methods <p>Patients with TAK from a prospective observational cohort who underwent ¹⁸F-FDG PET/CT and serological tests at baseline were included. Magnetic Resonance Angiography and/or Contrast-Enhanced Ultrasound were conducted at baseline and every six months during follow-up. The PETVAS was calculated. New/aggravated lesions were considered as angiographic progression.</p> Results <p>The imaging evaluation included 1,353 arterial territories from 123 patients. The baseline PETVAS was positively correlated with Erythrocyte Sedimentation Rate (ESR), serum IL-6, and Platelet. Angiographic progression was noted in 45 patients (36.6%) with 72 territories (5.3%) during 30 (18–72) months of follow-up. Of these, 19 (42.2%) had baseline PETVAS &gt; 15, including 84.2% (16/19) naïve cases and 78.9% (15/19) with ESR ≥ 30&#xa0;mm/h. Multivariate Cox proportional hazards regression analysis adjusted for age and sex showed baseline PETVAS &gt; 15 (HR 1.93; 95% CI, 1.01–3.68; <i>p</i> = 0.04) an independent predictor of angiographic progression.</p> Conclusion <p>Baseline PETVAS &gt; 15 was an independent predictor of angiographic progression in TAK. Baseline FDG uptake in specific arterial territories did not correlate with vascular progression. Our study provides a feasible PET/CT-based predictive marker for vascular progression in TAK and underscores the importance of regular imaging follow-up to monitor disease outcomes.</p> Clinical trial number <p>Not applicable.</p>