What is vascular sonography?
Doppler/duplex sonography is a type of ultrasound examination that measures the speed of blood flow in the vessels (arteries and veins). This makes it possible to reveal vasoconstriction and changes in blood circulation.
What is the examination procedure?
Doppler/duplex sonography on the vessels supplying blood to the brain is carried out like any other ultrasound examination. A gel is first applied to the corresponding area of skin so that the air between the transducer and skin does not reflect the ultrasonic waves. The ultrasonic transducer is guided over the affected region of the body. If, for example, there is a suspected narrowing of a cerebral artery, the lateral cervical or temporal region would be examined. The test is harmless, painless and there is no risk of bodily harm.
The ultrasound head emits ultrasonic waves at a specific frequency. When this bundle of sound waves collides with blood cells in the vessels, part of the wave is reflected, causing a change in its frequency. The change in frequency is a function of the speed and movement of the blood cells. This can be represented acoustically, for example. The velocity and direction of the blood cells change at vessel constrictions, resulting in a signal that differs from that of a normal vessel. Depending on the type of signal change, it is therefore possible to determine the extent of the vasoconstriction. In addition, the path of the blood vessels, the vascular caliber and the condition of the inner vascular layer can be evaluated, making it possible to precisely measure the wall thickness and arteriosclerotic deposits, such as calcified plaques.
When is a Doppler/duplex sonography performed?
Doppler/duplex sonography is a very routine method used to diagnose vascular diseases.
The method can be used to test the following:
- Direction of blood flow
- Vascular constrictions – this is important, for example, to detect or rule out a narrowing (stenosis) of the cerebral artery
- Changes in the vessel walls, e.g. calcifications
Success and progress following vascular surgery for cases of carotid stenoses can be monitored, for example.