Comparison of the utility of CT scans and intravascular ultrasound in endovascular aortic grafting.

Using CT scans and intravascular ultrasound (IVUS), aortic, aneurysm neck, and endoluminal graft cross-sectional dimensions were compared in a canine model before and after placement of endoluminal grafts in normal aortas (n = 10) and in artificially constructed abdominal aortic aneurysms (n = 15). Measurement of diameters (n = 83) revealed an average difference or bias between imaging modalities of 0.17 +/- 0.92 mm. Measurements obtained using IVUS were slightly larger than CT values (8.84 +/- 1.0 vs. 8.65 +/- 1.1, p < 0.03) but correlated very well by linear regression analysis (r = 0.948, p < 0.02). Analysis of cross-sectional area (n = 44) revealed an average difference or bias of 7.21 +/- 7.76 mm2 between the two modalities. Again IVUS measurements were larger than CT measurements (65.0 +/- 16.5 vs. 57.9 +/- 11.9, p < 0.001) and linear regression analysis showed less correlation (r = 0.897, p < 0.001). Qualitative assessment of the graft and stent characteristics was more precise using IVUS. Graft folding, stent-aorta interfaces, and thrombus formation were easily identified by IVUS, whereas these more subtle characteristics were missed by CT scanning and arteriography. These studies demonstrate that IVUS measurements were slightly larger than CT values; however, both modalities demonstrate small bias and good correlation. Qualitative analysis of the aneurysmal aorta and endoluminal graft using IVUS is comparable to and in some respects more detailed than measurements from CT scanning and arteriography.