Comparison of intravascular ultrasound, external ultrasound and digital angiography for evaluation of peripheral artery dimensions and morphology

Validation of catheter-based intravascular ultrasound imaging has been based on comparisons with histology and digital angiography, each of which may have limitations in the assessment of arterial size and morphology. External, high-frequency ultrasound can accurately determine vessel dimensions and morphology and because, like intravascular ultrasound, it also provides crosssectional arterial ultrasound images, it may be a more appropriate technique for the in vivo comparison of arterial dimensions and morphology determined by intravascular ultrasound. Thus, intravascular ultrasound, external 2dimensional ultrasound, Doppler color-flow imaging and digital angiography were compared for assessment of arterial dimensions and war morphology at 29 femeral artery sites in 15 patients. Intravascular ultrasound and the other 3 imaging modalities correlated well in determination of lumen diameter (2-Dimensional, r = 0.98, standard error of the estimate [SEE] = 0.14; Doppler color flow, r = 0.91, SEE = 1.11; angiography, r = 0.95, SEE = 0.91) and cross-sectional area (2-dimensional, r = 0.97, SEE = 0.04; Doppler color flow, r = 0.92, SEE = 0.14; angiography, r = 0.96, SEE = 0.08). However, lumen size measured by Doppler color flow was consistently smaller than that measured by the other 3 imaging modalities. Intravascular ultrasound detected arterial plaque at 15 sites, 5 of which were hypoechoic (soft) and 10 hyperechoic with distal shadowing (hard). Plaque was identified at 12 of 15 sites by 2-dimensional imaging (p = 0.30 vs intravascular ultrasound), but at only 6 of 15 sites by angiography (p = 0.003 vs intravascular ultrasound), only 1 of which was thought to be calcified plaque. These data indicate that arterial dimensions determined by intravascular ultrasound correlate well with both external ultrasound and angiography in normal and minimally diseased peripheral arteries. Doppler color flow underestimates true lumen size. Angiography is often discordant with both intravascular and external ultrasound in determining the presence and composition of arterial plaque. (Am J Cardiol 1991,-67:817-M)
Vascular imaging techniques are important for examining blood vessels for decreased size, vessel wall damage, accumulation of fatty plaque (hardened material stuck to wall of blood vessel) and other signs of disease. Currently used imaging techniques include external ultrasound, which uses high-frequency sound waves to image vessel dimensions and flow of blood vessels from outside the body, and digital angiography, which uses X-rays of vessels after a contrast material has been injected into them. A newly developed technique for these purposes is intravascular ultrasound. It also uses high-frequency sound waves for imaging purposes, but does so within the vessels by means of a catheter inserted into the vessels. This accuracy of this technique has not been completely validated and its results have conflicted with results from angiography regarding changes inside the vessel. Either intravascular ultrasound is more sensitive than older methods, or else it cannot accurately determine vessel morphology. All four imaging techniques were evaluated for measuring vessel dimensions and morphology to examine the accuracy of this intravascular ultrasound. Fifteen patients with no prior history of peripheral artery disease were examined using two-dimensional and Doppler external ultrasound, intravascular ultrasound, and digital subtraction angiography. Results from all four methods were approximately equivalent in measurements of vessel diameters and cross-sectional areas. Intravascular ultrasound detected 15 plaque sites, with external ultrasound finding 12 of these 15, and angiography imaging only 6 of them. On the other hand, neither angiography nor external ultrasound found plaque sites not found by intravascular ultrasound. Interpretations of angiography and intravascular ultrasound disagreed in 9 out of 10 cases of hard plaques as to whether the lesions were calcified. These results demonstrate intravascular ultrasound can determine vessel dimensions as well as other techniques. It also seems better able to find plaque sites. Further research needs to be done to see if is more accurate than angiography in characterizing these plaque sites. (Consumer Summary produced by Reliance Medical Information, Inc.)