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PERIPHERAL VASCULAR ULTRASOUND
ICA CCA
Figure 8.14 An image of a heterogeneous plaque with a crater (arrow) suggesting an ulcer.
Atheroma removed from the carotid bifurcation during carotid endarterectomy.
wall at its base, with flow vortices seen on color imaging). Figure 8.14 shows a heterogeneous plaque with a crater, filled with blood flow, sug- gesting an ulcer.
A slightly different method of categorizing the plaque, imaged in longitudinal views, was reported by Bock & Lusby (1992) whereby the plaque was graded from 1 to 4, as shown in Figure 8.15. Type 1 appears as an anechoic area seen to have a thin cap (Fig. 8.16A). Anechoic areas were shown to relate to either lipid or intraplaque hemorrhage. Echogenic plaques were categorized as type 4 and were considered to be more benign. Figure 8.16D demonstrates a more echogenic plaque. Types 2 and 3 were heterogeneous plaques (Fig. 8.16B and C), with type 3 appearing more echogenic than type 2. Plaque types 1 and 2 were seen significantly more frequently in symptomatic patients, whereas types 3 and 4 were more commonly found in asymptomatic patients.
These and many other studies over recent years suggest that the most useful quality of the B-mode appearance of a plaque is the proportion of
Anechoic
Type 1 AC
Type 2 BD
Echogenic
Type 3
Type 4
Figure 8.13
Figure 8.15 Plaque categorization based on ultrasound imaging described by Bock & Lusby. (From Bock & Lusby 1992, with permission.)
anechoic areas or areas of low echogenicity within the plaque. Clearly the appearance of a plaque is dependent on the scanner controls being set to give an optimal image. Studies have shown a correlation of histological appearance with an increased risk of ischemic cerebrovascular events (Mathiesen et al 2001); however, the benefits of surgery over medical treatment in the management of asymptomatic patients based on plaque appear- ance have not been proven. Several research centers