Doppler Ultrasound Test: What It is, What It Diagnoses and Results

What is a Doppler ultrasound?

A Doppler ultrasound is a type of ultrasound test that uses sound waves to visualise and produce images of the blood flow through your veins and arteries. This specialised form of ultrasound allows healthcare professionals to assess the speed and direction of blood flow, helping to detect heart conditions and other issues affecting the heart's function.

How does a Doppler ultrasound work?

Doppler ultrasound works by bouncing high-frequency sound waves off moving red blood cells in your bloodstream. As these red blood cells move through your bloodstream, they cause a change in the frequency of the reflected sound waves. This change in pitch between the sound waves sent into your body, and the echo that bounces back is known as the Doppler effect. Afterwards, the data is then measured and used to create images or graphs that show blood flow through your blood vessels and how fast the blood is moving.

What are the different types of Doppler ultrasounds?

There are several types of Doppler ultrasound exams, each serving a specific purpose:

1) Continuous wave (CW) Doppler 

• Piezoelectric crystals generate an electric charge when subjected to mechanical stress.

• Two sets of piezoelectric crystals are used; one set of piezoelectric crystals continuously emits ultrasound, while the other constantly receives the reflected waves.

• The frequency shift of the reflected waves is used to determine the velocity of the flow of blood.

2) Pulsed wave (PW) Doppler 

• The ultrasound machine uses short pulses to analyse the reflected sound waves. The ultrasound machine ignores signals except those reflected from the sample volume, allowing for precise velocity measurements at a specific location.

3) Colour Doppler

• A computer will change the sound waves to different colours. The process creates a colourful overlay on blood vessel images, showing real-time information about blood flow speed and direction of blood flow.

4) Power Doppler 

• This test is used to show the presence of blood flow and can be used to show very slow blood flow or study blood flow inside organs. However, it does not show the direction of blood flow.

5) Duplex ultrasound 

• This combines standard ultrasound imaging with Doppler ultrasound. Thus, it can show the width of blood vessels and any blockages affecting arterial blood flow.

Why do I need a Doppler ultrasound?

Your healthcare provider may suggest a Doppler ultrasound if you have symptoms of abnormal blood flow, or if they suspect that you may suffer from certain vascular conditions. Common reasons include:

• Assessing the risk of or diagnosing a stroke.

• Evaluating and monitoring blood flow after an injury, surgery or other treatments.

• Checking for blocked arteries, blood vessel damage or deep vein thrombosis (the formation of a blood clot in a deep vein).

• General concerns over your heart function.

• Assessing foetal health during pregnancy.

If you have any concerns about blood flow, or if you feel that any of the reasons above apply to you, please request an appointment with Thomson Medical.

Why would I need a Doppler ultrasound when pregnant?

A Doppler ultrasound is performed during pregnancy for several important reasons:

Monitoring foetal health and development

Doppler ultrasounds help assess the baby's overall health by evaluating blood flow through various foetal vessels, including the umbilical cord and major arteries. This allows healthcare providers to:

1. Monitor foetal growth and development

2. Detect potential foetal distress

3. Identify signs of foetal anaemia

4. Assess placental function and blood flow

Detecting complications

Doppler ultrasounds are also useful in identifying and monitoring high-risk pregnancies. They can help detect:

1. Intrauterine growth restriction (IUGR)

2. Preeclampsia risks

3. Congenital heart defects

4. Placental abnormalities

Assessing foetal blood flow

The colour Doppler technique provides a clear visualisation of the blood flow patterns in the developing foetus. This helps doctors:

1. Identify any obstructions in blood circulation.

2. Evaluate the function of the foetal heart and other organs.

3. Assess risks of premature birth.

Timing of scans

Doppler ultrasounds are typically performed:

• During the third trimester (31-40 weeks) to check for growth restrictions and heart abnormalities.

• Earlier (10-12 weeks) in high-risk pregnancies to screen for developmental abnormalities.

Doppler ultrasounds play a crucial role in ensuring the health and well-being of both mother and baby throughout pregnancy by providing detailed information about foetal blood flow and development.

Are you curious about your baby's development and want to check on the foetus's overall health? Request an appointment with Thomson Medical’s fertility specialists.

What is the process of getting a Doppler ultrasound?

How do I prepare for a Doppler ultrasound?

Preparation for a Doppler ultrasound will vary depending on your situation and the area being examined. Your healthcare provider may give you specific instructions, and ask you to:

• Fast for several hours before the test.

• Avoid smoking or nicotine products for at least two hours prior, as nicotine will cause the narrowing of blood vessels, affecting the results of the test.

• Wear comfortable, loose-fitting clothing.

What happens during a Doppler ultrasound?

During the procedure:

1. You'll lie on an exam table and remove clothing from the area being examined.

2. A sonographer, a specialist in ultrasound imaging technology, will apply a small amount of a special ultrasound gel, serving as a lubricant to your skin to help the transducer (a wand-like device) glide over and help the sound waves travel.

3. The transducer will send painless sound waves through your skin into your body. The sound waves are of a high frequency, and you will not hear them.

4. The sound waves will reflect off the moving blood cells, causing the pitch of the sound waves to change. You may hear whooshing sounds from the ultrasound machine as the device detects the blood flow.

5. The transducer detects the pitch changes in the sound wave, and a machine records the sound wave changes and converts them into images or graphs for your doctor to review.

6. The test usually takes about 30 to 60 minutes and is painless.

Are there any risks to getting a Doppler ultrasound?

Doppler ultrasound tests are generally considered safe when performed by trained professionals, such as sonographers. Moreover, unlike X-rays, it doesn't use ionising radiation, making it safer for repeated use and safe for use during pregnancy. It is overall a risk-free and pain-free procedure. However, an ultrasound can potentially affect body fluids and tissues, so it's recommended only when medically necessary.

Normal Doppler ultrasound results

Normal Doppler ultrasound results are characterised by:

• Regular waveform patterns: The visual representation of your blood flow displays expected peaks and troughs

• Appropriate blood vessel size: The diameter of blood vessels falls within normal range

• Normal velocity measurements: The speed of blood flow is within expected parameters

This typically means that you have consistent blood flow where your blood is flowing at an expected rate and direction through the examined vessels. It also indicates no significant blockages or narrowing of the blood vessels.

Your doctor might describe normal results using terms such as "no evidence of stenosis" (narrowing), "patent vessels" (open vessels), or "normal flow characteristics."

Abnormal Doppler ultrasound results

Abnormal findings on a Doppler ultrasound may include and indicate:

• Reduced or absent blood flow: This could suggest a blockage, clot, or severe narrowing

• Reversed flow direction: Blood flowing in an unexpected direction can indicate valve problem

• Irregular waveform patterns: Abnormal peaks and troughs can suggest vascular disease

• Vessel narrowing (stenosis): Narrowed areas may show increased blood flow velocity

• Vessel dilation or aneurysm: Abnormally widened blood vessels

• Turbulent flow: Chaotic blood flow patterns often seen near blockages or abnormal connections

What causes abnormal results?

Abnormal results can be caused by various factors, including:

1. Atherosclerosis (narrowing of blood vessels)

2. Blood clots

3. Congenital heart defects

4. Peripheral artery disease

5. Varicose veins

What do I need to consider?

It's important to follow your healthcare provider's instructions for preparation and to discuss your results thoroughly. If you feel like you may have any worries concerning your health regarding your blood flow, such as blood clots, or experience any symptoms of heart disease, it is best to discuss with them the best course of action tailored for you. Moreover, while a Doppler ultrasound is generally safe, it should only be used when medically necessary.

FAQ

Can Doppler ultrasound detect blocked arteries?

Yes, Doppler ultrasound can detect narrowed or blocked arteries by detecting abnormal blood flow patterns, by checking on any irregularities in the speed and direction of blood flow.

How is a Doppler test done on legs?

A Doppler test on legs involves applying gel to the skin and moving a transducer along the leg to examine and detect irregularities in blood flow within your arteries and veins.

What are the side effects of a Doppler test for legs?

There are typically no side effects from a Doppler test for legs. It's a non-invasive procedure. It is also a risk-free and painless procedure.

What are the symptoms of bad circulation in the legs?

Symptoms may include numbness, tingling, pain, cramping, swelling, and discolouration in the legs.

What is the reason for leg Doppler?

Leg Doppler tests are often performed to check for conditions like deep vein thrombosis, peripheral artery disease, or varicose veins.

What is the best treatment for blocked arteries in the legs?

Treatment will depend on the severity of the blocked leg arteries, and may include lifestyle changes, medication, angioplasty, or surgery. Your doctor will determine the best approach based on your specific condition.

Why would a doctor order a leg ultrasound?

A doctor might order a leg ultrasound to investigate blockage of leg arteries, and check for symptoms of poor circulation, check for blood clots, or monitor pre-existing vascular conditions.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please book a consultation with a specialist at Thomson Medical. Request an appointment with Thomson Medical today.