Feasibility of Diffusion-weighted MRI for Detecting Abdominal Aortic Endoleaks after Endovascular Aneurysm Repair

Background Unlike gadolinium-enhanced MR angiography, which relies on contrast enhancement, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping can be used to detect endoleaks based on differences in water molecule diffusion. Purpose To evaluate the diagnostic accuracy of DWI and ADC mapping combined with other noncontrast MR angiographic (NC-MRA) sequences for detecting endoleaks in participants after endovascular aneurysm repair. Materials and Methods In this single-center prospective study conducted between May 2022 and February 2024, 34 participants underwent CT angiography (CTA) and NC-MRA (including DWI, ADC mapping, fast imaging employing steady-state acquisition [FIESTA], inflow inversion recovery, and two-dimensional phase-contrast imaging) within 3 months. Two blinded reviewers assessed endoleaks independently in two sessions; the second session included ADC-FIESTA fusion images. Diagnostic accuracy of DWI with ADC mapping plus other NC-MRA sequences versus CTA was calculated, and interobserver agreement was assessed using Cohen κ. The ratios of the ADC value of the endoleak and of the adjacent thrombus to the ADC value within the aortic stent were calculated. Results DWI with ADC mapping plus other NC-MRA sequences achieved a sensitivity of 95% (19 of 20; 95% CI: 75, 100), a specificity of 93% (13 of 14; 95% CI: 66, 100), and an overall accuracy of 94% (32 of 34; 95% CI: 80, 99), compared with CTA (P = .48). The mean ADC ratio of endoleak to aortic stent flow was 0.97 ± 0.12 (SD), significantly higher than the mean ADC ratio of thrombus to aortic stent flow (0.52 ± 0.12; P < .001). With inflow inversion recovery, two type Ia endoleaks were detected, but type Ib and type II endoleaks were not detected. Interobserver agreement improved from κ = 0.60 to κ = 0.82 with the inclusion of ADC-FIESTA fusion images (P = .09). Conclusion DWI and ADC mapping combined with other NC-MRA sequences and ADC-FIESTA fusion images offers an accurate and noninvasive method for detecting abdominal aortic endoleaks. © RSNA, 2025 Supplemental material is available for this article.