Diagnostic ultrasound ( PDFDrive )

CHAPTER 26 The Extracranial Cerebral Vessels 921
E
F
G
H
FIG. 26.7, cont’d (E) Sagittal and (F) transverse images demonstrate homogeneous plaque (type 3). Associated calciications best seen on
image E obscure uniformity of plaque. (G) Sagittal and (H) transverse images demonstrate homogeneous plaque (type 3) in the carotid bifurcation.
The sonolucent areas are less than 50% of the volume of the plaque.
color or power Doppler. he plaque must be evaluated in both
sagittal and transverse planes. 46 Homogeneous plaque has a
generally uniform echo pattern and a smooth surface (Fig. 26.7).
Sonolucent areas may be seen, but the amount of sonolucency
is less than 50% of the plaque volume. he uniform acoustic
texture corresponds pathologically to dense ibrous connective
tissue (Videos 26.2 through 26.4). Calciied plaque produces
posterior acoustic shadowing and is common in asymptomatic
individuals (Fig. 26.8, Video 26.5). Heterogeneous plaque has
a more complex echo pattern and contains one or more focal
sonolucent areas corresponding to more than 50% of the plaque
volume (Fig. 26.9, Videos 26.6 through 26.11). Heterogeneous
plaque is characterized pathologically by containing intraplaque
hemorrhage and deposits of lipid, cholesterol, and proteinaceous
material. 15,73 Homogeneous plaque is identiied much more oten
than heterogeneous plaque, occurring in 80% to 85% of patients
examined. 47 Sonography accurately determines the presence or
absence of intraplaque hemorrhage (sensitivity, 90%-94%; speciicity,
75%-88%). 48,54,73,76-80
Some sources suggest classifying plaque according to four
types. Plaque types 1 and 2, similar to heterogeneous plaque
and much more likely to be associated with intraplaque hemorrhage
and ulceration, are considered unstable and subject to
abrupt increases in plaque size ater hemorrhage or embolization.
14,46,74,81-84 Types 1 and 2 plaque are typically found in
FIG. 26.8 Calciied Plaque. The calciied plaque creates a shadow
that obscures characterization of plaque in the left internal carotid artery.
symptomatic patients with stenoses greater than 70% of diameter.
Plaque types 3 and 4 are generally composed of ibrous tissue
and calciication. hese plaque types are similar to homogeneous
plaque. hese are generally more benign, stable plaques typically
seen in asymptomatic individuals (see Fig. 26.8).