Imaging modalities for aortic endografting.

Abstract

One of the most fundamental and influential differences between conventional surgery and endovascular grafting for aortic aneurysm is the central role of imaging in every aspect of management. This review summarizes five imaging techniques for aortic endografting: intravascular ultrasound, contrast angiography, conventional computed tomography (CT), spiral CT with image processing, and magnetic resonance angiography (MRA). External ultrasound and intravascular ultrasound have important relevance to endovascular aortic surgery. Artifacts of arteriography include magnification, thrombus effect, fore-shortening of tortuosity, loss of luminal detail, parallax error, and projection errors. Conventional CT scans have artifacts and difficulties also. Diameter measurement by CT suffers from methodology errors and observer variability. If conventional CT and angiography are used for endovascular aortic graft planning, both should be obtained since neither alone provides sufficient data. The use of spiral CT scanning and computerized image processing has clearly aided the preoperative definition of aneurysm morphology both in terms of dimensional accuracy and by adding diagnostic information. MRA is capable of producing three-dimensional images, axial sections, and longitudinal projections in any plane. It can detect blood flow without contrast medium, but gadolinium enhances MRA by avoiding the "signal dropout" artifact. Technology exists to provide new forms of imaging for endovascular surgery that combines three-dimensional models with on-line image data in a process called "data fusion." This may offer improved ease and accuracy for conducting endovascular procedures in the future.