MR Protocol After Endovascular Repair of Abdominal Aortic Aneurysms

--> MR Protocol and Technique


The routine protocol used at our institution for postoperative endovascular aneurysm repair surveillance includes unenhanced and contrast-enhanced T1-weighted images and axial T2-weighted and steady-state free procession (SSFP) images. The contrast material is administered dynamically and divided into two injections. The first injection is used for time-resolved MR angiography to aid in endoleak detection, and the second injection is used with higher-spatial-resolution MR angiography for better depiction of anatomy.

SSFP imaging produces high signal-to-noise ratio images with T2 and T1 weighting . Chronic thrombus shows low signal intensity, and noncoagulated blood exhibits high signal intensity on this sequence, making it an ideal tool for characterizing aneurysm sac contents and determining whether there is an endoleak or endotension

Imaging Characteristics in the Postoperative Patient



If there is no endoleak or endotension post-operatively, the aneurysm sac contents will show hypointensity on both T1-weighted and T2-weighted images, no areas of enhancement after dynamic contrast administration, and diffuse low signal on SSFP imaging. Typical MRI findings associated with endoleaks include aneurysm sac contents with intermixed areas of variably increased or decreased intensity on T1-weighted and T2-weighted images and areas of enhancement after dynamic contrast administration. These heterogeneous areas appear as increased signal on SSFP imaging, and correlation with site and direction of flow enables characterization of the endoleak type. MRI characteristics of endotension include aneurysm sac contents that show low T1 signal and high T2 signal, no areas of enhancement after dynamic contrast administration, and uniform high signal on SSFP imaging  In the setting of limb occlusion, there is no flow identified in the stent-graft