Doppler Ultrasound
Doppler ultrasound provides real-time images of blood flow through the use of sound waves. This non-invasive test is a useful tool for studying blood circulation in various organs of the body.
General Description
Doppler ultrasound is a non-invasive diagnostic technique that allows for the visualization of blood flow or circulation in real-time. It uses high-frequency sound waves that, when they bounce off red blood cells (also known as erythrocytes, hematids, or red blood cells) as they move, produce a frequency change known as the Doppler effect. Measurements are based on the fact that red blood cells moving away from the probe emit a different echo than those moving toward it.
Based on this frequency shift, certain calculations are made to determine the direction and speed of blood flow, the diameter of blood vessels, the presence of fatty or cholesterol plaques (atheroma), potential obstructions in veins and arteries, or the existence of inflammatory conditions in the vessels.
Different types of Doppler ultrasound can be used depending on the information needed:
- Color Doppler: The image is displayed in color to facilitate interpretation. By convention, red represents the flow moving toward the probe, while blue represents the flow moving away. The higher the speed, the brighter the colors.
- Power Doppler: A type of color Doppler commonly used to check blood flow in solid organs such as the kidney, liver, heart, lungs, or pancreas.
- Spectral Doppler: Uses pulsed wave (to show the direction of blood flow) or continuous wave (to measure blood flow speed) to capture the information and present it in a graph.
- Duplex Doppler: Uses conventional ultrasound to capture images of blood circulation, which are then represented graphically by a computer.
This procedure is used to check the state of blood circulation in any organ of the body, so it is also known as vascular Doppler ultrasound. It is commonly performed on:
- The legs or arms to check the blood flow in the large arteries and veins that supply them.
- The supra-aortic trunks (TSA Doppler ultrasound) to perform a hemodynamic and morphological study.
- The neck to evaluate the condition of the vessels running through it, specifically the carotid arteries and veins of the neck.
- The heart to examine both its structure and function (cardiac Doppler ultrasound).
- The kidney to assess its vascularization.
- The fetus during pregnancy to determine whether the blood flow it receives is sufficient for obtaining the oxygen and nutrients it needs.
When is it indicated?
Doppler ultrasound is performed to diagnose venous pathologies or to monitor the progression of certain vascular injuries. This procedure allows for the detection of clots, blockages, narrowing, aneurysms (bulging of arteries), decreased blood circulation in the arteries, or defects in heart or venous valves.
How is it performed?
Before the study begins, gel is applied to the skin to facilitate the transmission of sound waves. Then, the ultrasound transducer, which is a manual probe emitting sound waves, is placed on the area to be studied and moved over it. The images are seen on a computer in real time.
In some cases, a Doppler signal enhancer, which has no side effects and is not harmful to health, may be used. This is administered intravenously.
Risks
Doppler ultrasound does not pose any risk to health.
What to expect from a Doppler ultrasound
On the day of the test, it is recommended to wear comfortable clothing that can be easily removed, as the area to be studied must be exposed. A gown is usually provided at the medical center.
It is normal to feel cold when the gel is applied, but it is a sensation that passes quickly. The specialist may press on some points with the transducer to obtain clearer images, but this should not cause pain.
Doppler ultrasound is an outpatient procedure that lasts between 15 and 20 minutes and does not require hospitalization. Results are obtained immediately, but it is common for specialists to prepare a report that is explained to the patient in a follow-up consultation a few days later.
Specialties in which Doppler ultrasound is requested
Doppler ultrasound is a common test in the field of angiology and vascular surgery.
How to prepare
Preparation depends on the area of the body to be studied using Doppler ultrasound. Generally, it is important not to smoke or use nicotine products for at least two hours before the test, as this substance narrows blood vessels and can alter the results.
For abdominal exams, the specialist will inform you if fasting for six hours is required.
Diabetic patients or those on chronic medication should consult their specific case before attending the appointment.
