This document provides guidelines for performing sonographic assessment of the carotid arteries. It outlines the anatomy of the carotid arteries and optimal scanning techniques. The examination involves 8 steps: 1) inspecting carotid bifurcations with color Doppler; 2) identifying the external and internal carotid arteries; 3) checking blood flow directions; 4) measuring intima-media thickness; 5) evaluating plaques; 6) assessing vertebral and subclavian arteries; 7) documenting findings; and 8) interpreting scans. Optimal techniques include using high frequency linear transducers, adjusting the color scale and gain, and maintaining a 45 degree angle between the probe and artery.
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carotid doppler.pptx
1. SONOGRAPHIC ASSESSMENT OF
CAROTID ARTERIES
DR. JK PATIL
Prof. Department of Radio-diagnosis,
DY Patil medical college, hospital & research institute
Kolhapur
6. PROTOCOL
• PATIENT POSITION
•
Transducer
Higher-frequency linear transducers (7 MHz) are ideal for assessment of the
intima-media thickness and plaque morphology, while lowerfrequency linear
transducers (7 MHz) are preferred for Doppler examination. In a short muscular
neck, if imaging with a linear transducer is impossible, a curved-array transducer
(7 MHz) may be helpful to document the anatomy of the carotid bifurcation with
color Doppler US
20. OPTIMAL SCANNING TECHNIQUES AND DOPPLER SETTINGS
•
where f is the Doppler shift frequency,
f0 is the transmitted ultrasound frequency,
V is the velocity of reflectors (red blood cells),
(theta, also referred to as the Doppler angle) is the angle between the transmitted beam and the direction of
blood flow within the blood vessel (the reflector path), and
C is the speed of sound in the tissue (1540 m/sec)
31. IMAGING PROTOCOL :IMT & PLAQUE
• B-mode image is taken at the distal common carotid artery. The head of the patient is
rotated 45 degrees away from the side being imaged and the probe is held parallel to the
artery
• The probe is kept parallel to the artery so that he double lines of the lumen-intima and
media adventitia interfaces are clearly visible on both near and far walls.
• The location of the common carotid IMT measurement is always below the bulb
extending to the right over a distance of approximately 1 cm
Amaurosis fugax is a temporary loss of vision in one or both eyes due to a lack of blood flow to the retina.
A carotid bruit is a vascular sound usually heard with a stethoscope over the carotid artery because of turbulent, non-laminar blood flow
(A) Transverse image of the left internal carotid artery (I) and external carotid artery (E). The internal carotid artery is lateral and larger in relation to the external carotid artery. (B) Color Doppler image of the left internal carotid artery (I) and the external carotid artery (E). Note normal color-low separation in the internal carotid artery
Image of the carotid artery bifurcation. The bulb (above the red line) is defined as being the zone of dilatation of the distal (CCA) to the level of the flow divider (arrow; the junction of the [ICA]) and (ECA).
This diagram shows the key landmarks of the carotid artery bifurcation. The flow divider is also the location of the carotid body nerve complex.
Transducer positions carotid usg examination. (A) This position is
used to perform a transverse sweep from the clavicle to the angle of the jaw. (B) The lateral projection is approximately 45 degrees from the horizontal and is a default position of the transducer for the longitudinal view. (C) The far posterolateral position is an additional projection that is occasionally used to visualize the distal internal carotid artery. (D) The anterolateral projection can sometimes help visualization in patients with very thick necks
(A) (CCA) is clearly visualized; the Doppler sample volume is as low in the neck as possible. (B) The Doppler velocity values tend to decrease with distance
from the aorta. The CCA is clearly visualized and the Doppler sample volume is central in the artery and below the carotid bulb. The CCA Doppler sample volume needs to be 2 cm or more below the bulb if internal carotid artery peak systolic to CCA peak systolic velocity ratios are used to assess the severity of any carotid stenosis. ED, End-diastolic; PS, peak systolic.
This color Doppler image shows a simple way of distinguishing ICA & ECA
. ECA branches are clearly visualized allowing immediate identification of the vessel.
rapidly pressed and released Pressure on the preauricular portion of the
superficial temporal artery. This temporal tap maneuver generates sharp deflections (arrows) on the external carotid artery waveform.
(A) The proximal internal carotid artery (ICA)(Prox ICA) waveform may have some distortion caused by the proximity to the bifurcation and the carotid sinus.
(B) The more distal ICA (Mid ICA) has the more typical Doppler waveform appearance and the end-diastolic velocity tends to increase (compare 36 cm/s at this location
to the sample in A near the bulb where it is 23 cm/s). ED,
the arrows indicate the location of the dicrotic notch, the transition from systole
to diastole. Low CCA: Waveforms in the very low common (CCA) show mild pulsatility because of the closeness of their origin from the aorta. There is a moderate amount of blood flow throughout diastole. High CCA:Waveforms in the CCA close to the bifurcation show moderately broad systolic peaks and a moderate amount of blood flow throughout diastole. ECA:) waveforms have sharp systolic peaks, pulsatility because of reflected waves from its branches, and relatively little flow in diastole as compared to the ICA.
ICA waveforms have broad systolic peaks and a large amount of flow throughout diastole.
(A) Left ECA shows a sharp systolic upstroke with relative low velocity and diastolic low (arrow), indicating a high resistive vessel. Note temporal tap conirming ECA. (B) Normal spectral pattern for ICA showing large amount of end diastolic low consistent with low resistive low. Angle theta is 52 degrees. Peak systolic velocity (PSV) is 63.3 cm/sec and end diastolic velocity (EDV) is 30.8 cm/sec. (C) Normal distal CCA waveform is a composite of low resistive ICA and higher resistive CCA waveform. PSV is 67.9 cm/sec and EDV is 25.4 cm/sec. PSV ratio of the ICA/CCA (63.3/67.9) is normal, measuring 0.9. Normal EDV ratio (30.8/25.4) is 1.2.
At a Doppler angle of 0°, the maximum Doppler shift will be achieved since the cosine of 0° is 1. Conversely, no Doppler shift (no flow)will be recorded if the Doppler angle is 90° since the cosine of 90° is 0
Location and angle of the sample volume in a diseased ICA with soft plaque. LT left, SV
sample volume. (a) Color Doppler image shows the sample volume angle incorrectly aligned with the wall contour of the ICA. The PSV reading in the ICA is 229 cm/sec, resulting in overestimation of the degree of stenosis as more than 70%. (b) Color Doppler image shows the sample volume angle correctly aligned with the flow vector
(the contour of the soft plaque). The resultant PSV reading in the ICA is 161 cm/sec; thus, the degree of stenosis
was reclassified as 50%– 69%.
Location of the sample volume box in a tortuous artery. Color Doppler image shows a tortuous left (LT) ICA. The change in the color depiction of the ICA is not due to a change in blood flow velocity but instead reflects changing direction of the blood flow relative to the Doppler angle of incidence. To sample the velocities at points B and C, the color box and angle of incidence require operator correction of the Doppler angle of incidence by steering the color box or angling the transducer. In this case, the correct position of the sample volume box is at point A
High-Grade (ECA) Stenosis. Elevated velocities and visible narrowing. Spectral broadening is present. Color Doppler spectral broadening is also seen.
Adjustment of the color Doppler sampling window. (a) Color Doppler image shows that the leftward position of the color Doppler sampling window results in a poor Doppler angle of incidence to the direction of blood flow in the proximal ECA. The result of an angle of incidence of almost 90° is ambiguous color display in this segment of the ECA. (b) Color Doppler image shows that correcting the angle of incidence by changing the position of the color Doppler sampling window or angling the transducer improves depiction of this area and is crucial for accurate velocity measurements
Adjustment of the color scale in a carotid artery stenosis. (a) Color Doppler image obtained with the color scale set too low (4 cm/sec) shows aliasing in the entire segment of the ICA.
(b) Color Doppler image obtained with the color scale set too high (115 cm/sec) shows no aliasing
Color Doppler image obtained with the optimal color scale setting shows the region of highest velocity, which corresponds to the narrowest segment of the ICA. Velocity sampling should be performed at this site.
Adjustment of the color scale in a near occlusion. (a) Color Doppler image obtained with the color scale set at 46 cm/sec shows a false-positive appearance of absent flow in the left ICA. (b) On a color Doppler image obtained with the color scale setting lowered to 4 cm/sec, trickle flow is evident, thus indicating the correct diagnosis of a near occlusion in the left ICA. Note the color noise in the background (arrowheads), which is a reassuring indicator of the optimal color gain setting for low-velocity flow.
Adjustment of the color gain. (a) Color Doppler image obtained with the color gain set at 80% shows marked turbulence in both the ICA and ECA, but no luminal narrowing is evident. (b) On a color Doppler image obtained with the color gain lowered to 66%, the anatomy of the bifurcation is demonstrated more accurately. The improved demonstration of the anatomy aids accurate placement of the sample volume box on the narrowest segment, with subsequent alignment of the Doppler angle parallel to the flow vect
Longitudinal image of the distal common carotid artery during end-diastole). The white arrows indicate the location of the lumen-intima interface of the far wall. The black arrows indicate the media-adventitia interface of the far wall. The vertical white line indicates the beginning of the common carotid artery far wall divergence. The distance between both interfaces (arrows) is the IMT
(A) The following diagram shows the sampling directions used to image the carotid
bulb/proximal internal carotid artery on the following images. (B) On the anterior projection,
the flow divider (short fat arrow) is identified between the (ICA) and the
(ECA). In addition, a plaque is well visualized (long arrow). (C) On the
lateral or standard projection, most of the image includes the proximal ICA. The flow divider and the plaque are barely visible. (D) On the posterior projection, the flow divider and the plaque are no longer visible. (E) These paired diagrams summarize, the effect of projection for images B, C, and D.
Different types of plaque seen on ultrasound. (A) Type 1, dominantly echolucent with a thin echogenic cap. (B) Type 2,
substantially echolucent lesions with small areas of echogenicity. (C) Type 3, dominantly echogenic lesions with small areas of echolucency
of <25%. (D) Type 4, uniformly echogenic lesions.
Homogeneous plaque. shows an echogenic soft homogeneous plaque in
the proximal right ICA. smooth the surfaceof the plaque is (arrowheads). This smoothness may indicate that the plaque is stabl grade 1 (B) shows a heterogeneous plaque in theproximal right ICA. irregular surface of the plaque, which contains echogenic and echopoor areas. This type of plaque is considered unstable. Grade 2
An ulcerated plaque. A thin rim is seen on the B-scan image (A) but colour Doppler (B) shows flow within the plaque.
Intraplaque hemorrhage. Grayscale US image shows a plaque containing an echo-poor area (arrow), which may be due to hemorrhage or lipids. In contrast to fat deposits, intraplaque hemorrhage is associated with a rapid increase in the size of the plaque, which is more likely to become symptomatic.
Moderate (50% to 69%) internal carotid artery
(ICA) (A) Gray-scale image shows a moderate amount of soft and calcific plaque
in the right carotid bulb, extending into the proximal
ICA. (B) Color Doppler image suggests a greater degree of stenosis than was apparent on the gray-scale images. (C) Spectral Doppler suggests a 50% to 69% stenosis
based on mildly (PSV =139 cm/s) (EVD = 60 cm/s). PSV ratio was also elevated to 2.4.
Severe (≥70%) internal carotid artery (ICA) stenosis in a with history of multiple transient ischemic attacks (TIAs) referable to the right
hemisphere. (A) Spectral Doppler image of the distal right common carotid artery (CCA) demonstrates a peak systolic velocity (PSV) of 70.5 cm/s. (B) Color Doppler image from
the ipsilateral ICA shows a dense calcific plaque with posterior acoustic shadowing beyond which is an area of intense color aliasing suggesting elevated velocities.
Spectral Doppler image confirms marked velocity elevation All three parameters are consistent with a 70% or greater stenosis
PW Doppler image of the proximal right ICA shows a tardus-parvus waveform. A severe proximal stenosis behind the shadowing plaque is suspected;
Color Doppler image of the right ICA and carotid bulb shows no flow in the ICA lumen and reversed flow in the bulb at the point of occlusion. The red and blue arrows indicate the direction of the reversed flow at the point of obstruction (thud flow). The PW Doppler spectrum also demonstrates thud flow, which manifests as damped systolic flow and reversed flow in early diastole
Internalization of the ECA. Color Doppler image of the left carotid bifurcation shows no flow in the distal CCA. The ICA and ECA are both patent, but flow in the ECA is reversed to supply antegrade flow in the ICA above the level of the occluded CCA. The curved arrows indicate the direction of blood flow from the ECA to the ICA
PW Doppler spectrum in internalization of the ECA. PW Doppler spectral image shows a reversed low resistive flow pattern with delayed systolic acceleration (tardus wave) in the ECA. The patient had an occluded CCA. In addition, reflections from the temporal tap maneuver are demonstrated as ripples in the Doppler spectrum
Vertebral artery Doppler spectrum. The vertebral artery Doppler spectrum is similar to that of the internal carotid artery. It should be noted that the flow directions of the vertebral artery and vertebral vein are opposite each other.
TAPV timed avg peak velocity Pgmean peak instantaneous systolic pressure gradient
Occult and partial subclavian steal. (a) PW Doppler spectral image of the right vertebral artery shows midsystolic deceleration with antegrade late-systolic velocities (occult steal)
PW Doppler spectral image obtained after the patient exercised the right arm (by opening and closing the hand for 2 minutes). The Doppler spectrum shows midsystolic deceleration with retrograde late-systolic velocities. The subclavian artery “steals” blood from the vertebral artery to supply the ischemic arm
Complete subclavian steal. PW Doppler spectral image of the left vertebral artery shows completely reversed flow.
