In vitro image characteristics of an abdominal aortic stent graft: CTA versus 3D MRA

Percutaneous stent-grafting is increasingly employed as a less invasive alternative to surgery for the treatment of infrarenal abdominal aortic aneurysms. It requires long-term imaging follow-up, to document the structural integrity of the device, to exclude perigraft channels and endograft leakages, as well as the shrinkage of the aneurysmal sac. The expectation of severe stent induced artifacts and safety concerns have prevented 3D MRA from being used. The purpose of this in vitro study was to investigate the imaging characteristics of a bifurcated stent graft with 3D MRA (3D Fourier transform fast spoiled GRE) at 1.5 T in comparison to those of CTA. Measurement of the stent wall thickness and luminal diameter were made on a agar gel embedded stent graft at five locations on both CTA and MRA images. The stent graft was depicted as a dark ring on MR images. Wall thickness measurements at the five locations of the stent graft overestimated the true stent thickness, while luminal diameters were slightly underestimated. Measurement differences between MR and CT were not statistically significant (P = 0.67; P = 0.85). Artifacts emanating from the platinum markers were considerably less severe on the MR-images. A wider area of signal loss was seen only at the insertion of the iliac stent leg into the aortic stent portion due to the overlap of two radio-opaque platinum markers. 3D MRA images should permit a comprehensive assessment of the arterial lumen, and of perivascular tissues.