Inter-Center Radiation Variability in CO 2 -Guided EVAR: Lessons From the Zero Iodine Contrast Multicenter Prospective Study

Introduction: Current diagnostic reference levels (DRLs) for endovascular aortic repair (EVAR), based on iodinated contrast media (ICM) protocols, range from 100 to 200 Gy·cm2. As CO2 is a negative contrast agent requiring digital subtraction angiography (DSA) for visualization, it may be associated with increased radiation exposure. This multicenter study presents the largest prospective data set to date evaluating radiation dose during EVAR using CO2 angiography alone with an automated injector. Methods: A prospective, multicenter, nationwide, nonrandomized, investigator-initiated observational study of dosimetry recorded during EVAR procedures with CO2 as exclusive contrast medium was conducted. Primary endpoints included dose-area product (DAP) and reference air kerma (Kar) measurements across all participating centers. Secondary objectives focused on evaluating optimization strategies to reduce radiation exposure for both patients and operators at a single investigational site. Results: A total of 293 patients were enrolled across 10 centers, between January 2023 and January 2024, median DAP and Kar were 189 Gy·cm2 (interquartile range [IQR] 107-285) and 626.5 mGy (IQR 145.5-1373.5), respectively, with significant inter-center variability (all p<0.001). Newer angiographic systems demonstrated markedly lower DAP (median: 90 Gy·cm2, IQR 71-153) vs older systems (191 Gy·cm2, IQR 111-409; p<0.001). Through sequential optimization, we achieved progressive dose reductions: 38.5% via low-dose protocols, 52.3% with modern equipment, culminating in a 56% overall reduction (p<0.001) with synchronized CO2-DSA—yielding a final median DAP of 28.5 Gy·cm2. Conclusions: CO2-guided EVAR exhibits substantial radiation dose variability, driven by angiographic system generation, software, and synchronization protocols. Modern systems with optimized low-dose protocols and CO2-DSA synchronization reduce radiation exposure to levels comparable to ICM-based EVAR. Clinical Impact: This large multicenter prospective study establishes a reliable radiation dose benchmarks for CO2-guided endovascular aortic repair (EVAR), showing that modern angiographic systems with optimized low-dose protocols and synchronized CO2-digital subtraction angiography achieve median dose-area product values comparable with conventional iodinated contrast media EVAR, thereby dispelling concerns about excessive radiation exposure with CO2-guided EVAR.