Time-Enhancement Curve of Four-Dimensional Computed Tomography Predicts Aneurysm Enlargement with Type-II Endoleak after Endovascular Aneurysm Repair

Objective We investigated the hemodynamic features of Type-II endoleaks after endovascular aneurysm repair (EVAR) using four-dimensional (4D) computed tomography (CT) to identify patients with aneurysm enlargement. Methods During a 13-month period (January 2017-January 2018) at our institution, we performed 4D-CT examinations in 13 patients after EVAR because of suspected Type-II endoleaks. Three patients were excluded from the study because of other endoleaks or absence of detectable endoleaks. The ramaining 10 patients were divided into two groups: enlargement group (n = 4), in which the aneurysm volume increased, and stable group (n = 6), in which the aneurysm remained stable or shrank. A CT scanner and three-dimensional workstation were used. All images were obtained using a consistent protocol (22 phase scans using the test bolus tracking method). We analyzed the hemodynamics of the endoleak cavity (EC) relative to those of the aorta and evaluated the time-enhancement curves (TECs) using measurement protocols. The strengths of correlations between these factors in the two groups were analyzed statistically. Results TECs in the enlargement group showed a more gradual curve, and the upslope, the gradient of TEC in the ascending phase and the upslope index were significantly more gradual than those in the stable group (p = 0.0247, 0.0243). The EC washout and the EC washout index were also more gradual than in the stable group's (p = 0.019, 0.019). The enhancement duration was longer in the former than in the latter (80%, p = 0.0195; 70%, p = 0.0159; 60%, p = 0.0159). The CT number in the equilibrium phase was larger in the enlargement group than in the stable group (p = 0.019). Conclusion The 4D-CT is useful for predicting aneurysm enlargement with Type-II endoleaks after EVAR.