Color-coded Doppler sonography

In the color-coded Doppler sonography The doctor uses an ultrasound device to examine the vascular structures of the body, making use of the physical Doppler effect, which is based on different sound frequencies from objects moving faster and slower. During the examination, a transducer sends a sound into the body, which is reflected back by the blood at different frequencies, the respective sound frequency being determined by the distance and speed of movement of the blood.

The individual frequencies and speeds are displayed in different colors by a connected computer and thus help the doctor to localize vessels and to discover circulatory disorders as well as thromboses or functional disorders of the heart.

What is color-coded Doppler sonography?

Color-coded Doppler sonography is an examination of the vessels. Ultrasound technology forms the practical basis for this process. The physical principle of the Doppler effect is the theoretical basis of the investigation.

With the Doppler effect, physics describes a change in the frequency of sound waves as soon as they are reflected or distributed by a fast moving object. With a sirloin quickly approaching and retreating, the person standing by hears the tone, for example, at frequencies that change with distance. Color-coded Doppler sonography transfers this principle to human blood and sends sound waves into the vessels. Depending on the distance and direction of blood flow, the sound waves sent come back at different frequencies.

The data obtained in this way are recorded by a computer and coded with different colors. Both the direction of flow and the flow rate of the blood can be displayed using different color markings. In this way, the doctor can also assess the exact location of blood vessels, arteries and veins and assess thromboses or changed vessel walls. The examination of the carotid arteries, the assessment of the flow conditions from the heart and the assessment of the kidney blood flow are important areas of application for the color-coded vascular examination.

Function, effect & goals

Color-coded Doppler sonography is primarily used to diagnose circulatory disorders. The method is able to differentiate the arterial blood flow from the venous blood flow. The examination thus enables the doctor to make statements about the overall blood flow. The procedure can also reveal smaller vessels that cannot be visualized using other techniques.

In many cases, this form of Doppler sonography is also used to find and evaluate heart muscle defects and impaired functions of the heart valve. For the patient, the examination is a more or less normal ultrasound examination. In preparation, ultrasound gel is applied to the relevant areas. The transducer of an ultrasound device is then passed over the areas and sends a sound through the skin into the body during the examination.

This sound reaches the flowing blood inside and is thrown back in the form of a reflection. The frequency of the reflected sound depends on the spatial sensitivity and distance of the blood from the transducer. A measuring sensor on the ultrasound device records the different tones. A computer is connected to the device, which evaluates the transmitted data and codes the various frequencies with a different color tone. Blood shown in red corresponds, for example, to blood flowing towards the transducer.

On the other hand, when the blood flow moves away from the transducer, the frequency of the reflected sound changes and the computer encodes the new sound frequency with blue color. Color-coded Doppler sonography also shows the flow rate of the blood. In order to differentiate between fast and slow flowing blood, the connected PC codes faster blood movements to the transducer, for example with a lighter red. In the same scheme, blood flowing away from the transducer is shown in a lighter blue. A blood flow moving slowly away from the transducer is given a dark blue code. A blood flow slowly moving towards the head, in conclusion a dark red one.

Risks, side effects & dangers

As a non-invasive method of vascular examination, color-coded Doppler sonography is not associated with any risks, pain or side effects for the patient and neither does it require hospitalization.

The accuracy in the localization of circulatory disorders is the main specialty of the procedure. The principle of Doppler sonography differs from other potential methods of vascular examination in particular in the relatively precise representation of the smallest vascular structures. Color-coded Doppler sonography is therefore superior to conventional examination methods in this field in many respects and has meanwhile been developed into many additional methods. Tissue and power Doppler sonography, for example, are based on the same principle.

With the tissue variant, not only the blood flow but also movements of the tissue can be displayed. In addition to the values ​​of the color-coded Doppler, the Power Doppler also determines the specific energy of the flowing blood. The importance of the Doppler effect for medicine is therefore revolutionary, because the precise localization is particularly important in the case of a circulatory disorder of the myocardium. In the case of such incorrect blood flow to the muscle tissue layer between the outer and inner skin of the heart, color-coded Doppler sonography can, for example, provide a framework for potential therapeutic methods, while other methods are not able to do so due to their lack of accuracy.