Doppler technology combined with ultrasound uses the high frequency sound waves directed at red blood cells and their movement, thus detecting the speed and direction of blood flow through the heart or through the vessels.

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Applications for the heart are discussed in the section of Cardiac Echos. In the rest of the body Doppler ultrasounds have two other applications:

 

Arterial Dopplers

Detect the speed and flow of blood in the arteries as well as narrowing of arteries or out right obstruction. Examples include:

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• Blood clots in arteries

• Arteries blocked for other reasons (such as external pressure)

• Decreased blood circulation in the legs (peripheral vascular disease)

• Bulging arteries (such as aortic aneurysms discussed in the Abdominal Ultrasound section)

• Narrowing of arteries, such as in the neck

 

The last example is one of the more important applications of arterial dopplers. The examination is called Carotid Dopplers. This looks at the major arteries of the neck, primarily to detect carotid artery stenosis, which is narrowing of the neck arteries caused by clots or plaque formation due to raised cholesterol. These conditions are major risk factors for transient ischaemic attacks or stroke.

 

Venous Dopplers

Detect the speed and flow of blood in the veins. Examples of possible diagnoses include:

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• Blood clots

• Deep Vein Thrombosis, most commonly in the calves

• Poorly functioning valves in the legs causing venous insufficiency and swollen legs

• Venous Mapping, studying the structure and haemodynamics of varicose veins

 

This last investigation is used to both monitor the progression of the condition of varicose veins, as well as to plan for surgery of the veins.