Ultrasonography.  2014 Jan;33(1):11-17.

General principles of carotid Doppler ultrasonography

• Lee W

Abstract

Carotid Doppler ultrasonography is a popular tool for evaluating atherosclerosis of the carotid artery. Its two-dimensional gray scale can be used for measuring the intima-media thickness, which is very good biomarker for atherosclerosis and can aid in plaque characterization. The plaque morphology is related to the risk of stroke. The ulceration of plaque is also known as one of the strong predictors of future embolic event risk. Color Doppler ultrasonography and pulse Doppler ultrasonography have been used for detecting carotid artery stenosis. Doppler ultrasonography has unique physical properties. The operator should be familiar with the physics and other parameters of Doppler ultrasonography to perform optimal Doppler ultrasonography studies.

Keyword

Carotid arteries; Atherosclerosis; Ultrasonography; Ultrasonography, Doppler; Plaque, atherosclerotic

MeSH Terms

Atherosclerosis
Carotid Arteries
Carotid Stenosis
Plaque, Atherosclerotic
Stroke
Ulcer
Ultrasonography
Ultrasonography, Doppler*
Ultrasonography, Doppler, Color

Figure

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  Fig. 1. Typical Doppler spectrum of the internal carotid artery and the external carotid artery. A. The Doppler spectrum of the internal carotid artery shows a low resistance pattern with sufficient diastolic antegrade flow. B. The external carotid artery shows a more resistive pattern than the internal carotid artery. Another differentiating sign is temporal artery tapping. The Doppler spectrum of the external carotid artery without temporal tapping (S) and with temporal tapping (W) shows a difference in the wave form. The pressure of the temporal tapping is shown on the diastolic pulse spectrum of the external carotid artery.

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  Fig. 2. Measuring of the intima-media thickness. A. The distal carotid artery is the proper site for measuring the intima-media thickness. The two clearly visible hyperintense lines (arrows) that represent the interface between the blood pool and intima layer and the interface between the media layer and adventitial layer should be noted on the image. B. An example of automatic intima-media thickness measurement is shown.

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  Fig. 3. The plaque morphology. A. A gray-scale image of a longitudinal scan of the distal common carotid artery shows plaque with mixed echogenicity (arrow). A calcification is visible (arrowhead). The plaque surface is smooth. B. A transverse scan of the plaque at the distal common carotid artery shows central low echogenicity (arrow). The more lucent plaque is known to be associated with a higher risk of the stroke.

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  Fig. 4. Three-dimensional ultrasonography to measure the volume of the plaque. The total plaque volume can be measured by threedimensional ultrasonography. The plaque contour is traced manually and then the volume of the plaque is calculated.

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  Fig. 5. Heel and toe technique. Tilting the probe from the head side to the toe side creates an angle between the probe surface and the vessel. A. For intima-media thickness measurement, the probe surface should be parallel to the vessel. B. For detecting a color signal and measuring flow velocity, an angle of at least 30° between the probe surface and the vessel is needed.

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  Fig. 6. 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.

Reference

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