Diagnostic ultrasound ( PDFDrive )

934 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
FIG. 26.24 Color Doppler Bruit. (A) Extensive soft tissue color Doppler bruit (arrows) surrounds the carotid bifurcation with a 90% internal
carotid artery (ICA) stenosis. (B) ICA demonstrates a small bruit, not as signiicant as in view A, but nevertheless a bruit showing the appropriate
area to place the cursor for Doppler low evaluation of the signiicant stenosis.
represent one of the earliest changes of atherosclerotic disease. 127
he low reversal seen in the region of the carotid bifurcation
is clearly diferent than that seen with color Doppler aliasing.
Contiguous saturated areas of red and blue are seen in this
low-velocity low separation versus the very diferent contiguous
color hues representing the highest color assignments for forward
and reversed low.
Helical low in the CCA may be an indirect indication of
proximal arterial stenosis but can occur as a normal variant.
Color Doppler sonography graphically displays the eccentric
spiraling of low up the CCA.
Advantages and Pitfalls
Color Doppler ultrasound may help avoid potential diagnostic
pitfalls. Alterations in cardiovascular physiology, tandem
lesions, contralateral carotid disease, arrhythmias, postoperative
changes, and tortuous vessels can lead to underestimation or
overestimation of the degree of stenosis. In such cases, color
Doppler ultrasound can provide direct visualization of the patent
lumen in a fashion analogous to angiography. 129 In fact, because
angiography images only the vessel lumen and not the vessel
wall, color Doppler and power Doppler ultrasound imaging
have the potential to evaluate stenoses even more completely
than angiography. Because low patterns are displayed with color
Doppler imaging, the local hemodynamic consequences of the
lesion are readily discerned. Color and power Doppler ultrasound
have particular value in detecting small residual channels of low
in areas of high-grade carotid stenoses 124,125,129-134 (Fig. 26.25).
Power Doppler ultrasound ofers a comparable advantage and
has the theoretical potential to be more sensitive for detecting
extremely low-amplitude, low-velocity low. Finally, color Doppler
and power Doppler ultrasound have the potential to clarify image
Doppler mismatches, further improving diagnostic accuracy and
conidence.
FIG. 26.25 High-Grade “String Sign” Stenosis of Internal Carotid
Artery. Tardus-parvus waveform with low velocity in a long segment.
Color Doppler Evolution of Carotid Stenosis
ADVANTAGES
Reduction in examination time
Quick identiication of areas of stenosis/high velocity,
which facilitates spectral analysis to artifacts
Improved diagnostic reproducibility and conidence
Distinguishes occlusion from “string sign”
Simultaneous hemodynamic and anatomic information,
velocity, and directional blood low information
Improved accuracy in quantitating stenoses
Clariies pulsed Doppler/image mismatch
DISADVANTAGES
Prone to angle dependence
Resolution less than with gray-scale
Slower frame rates information
Cannot characterize plaque