Diagnostic ultrasound ( PDFDrive )

932 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
C
D
E
FIG. 26.23 Near Occlusion (95%-99% Stenosis) With
Homogeneous Plaque. (A) Transverse and (B) sagittal gray-scale
images of the left ICA demonstrate homogeneous (type 3) plaque.
(C) Transverse and (D) sagittal power Doppler images demonstrate
extremely narrowed residual lumen. (E) Velocity measurements
for the ICA were peak systolic velocity, 51 cm/sec; acoustic Doppler
velocity, 19 cm/sec; systolic velocity ratio, 51/64 = 0.8; diastolic
velocity ratio, 19/12 = 1.5. The combination of visual images and
Doppler spectral analysis indings indicates a 95% to 99%
stenosis.
institution uses Table 26.2, which has a category for 80% to 95%
stenoses; our surgeons are more inclined to consider surgery for
patients with asymptomatic stenoses greater than 80% than for
those with less severe stenoses. 45,123
he ICA values should be obtained at or just distal to the
point of maximum visible stenosis and at the point of greatest
color Doppler spectral abnormality. Values from the CCA should
be obtained 2 cm proximal to the widening in the region of the
carotid bulb. Because velocities normally decrease from proximal
to distal in the CCA and increase from proximal to distal in the
ICA, it is important that standardized levels be used routinely
for obtaining the ICA/CCA velocity ratio.
Color Doppler Ultrasound
Color Doppler ultrasound displays blood low information in
real time over the entire image or a selected area. Stationary sot