Vascular Ultrasound in Ajax: How Blood Flow Imaging Works

Your circulatory system is a network of arteries and veins that stretches through every part of your body. Arteries carry oxygen-rich blood away from the heart; veins carry blood back to it. Most of the time it works silently, and you never think about it. But when a doctor needs to know how well blood is moving through a particular vessel, whether a vein might contain a clot or whether an artery has become narrowed, one of the most useful tools available is vascular ultrasound.

This article explains how vascular ultrasound works, from the basic physics of sound waves to the colour and audio signals your technologist uses during the exam. It also covers the reasons doctors commonly order the test and what the appointment is like for patients in Ajax and nearby communities. The aim is to take some of the mystery out of a test that many people find themselves booked for with little explanation.

Sound waves, not radiation

Ultrasound imaging is based on a simple principle. A handheld device called a transducer sends high-frequency sound waves into the body. These waves are far above the range of human hearing. As they travel through tissue, they bounce off structures such as muscle, vessel walls and moving blood cells. The transducer picks up the returning echoes, and a computer turns them into a live image on screen.

Because ultrasound uses sound rather than X-rays, there is no ionizing radiation involved. That is one reason it is widely used for repeated monitoring and why it is a common first choice for looking at blood vessels. It is also non-invasive: nothing is injected, and nothing enters the body.

A clear gel is placed on the skin before the transducer touches it. The gel removes tiny pockets of air between the transducer and the skin, since air blocks sound waves and would make the image unclear. It may feel cool at first and wipes off easily afterwards.

The Doppler effect: how ultrasound “sees” movement

A standard ultrasound image shows structures in shades of grey. That is useful for seeing the walls of a blood vessel or a buildup within it, but it does not on its own show how blood is flowing. For that, vascular ultrasound relies on something called the Doppler effect.

You have experienced the Doppler effect any time a siren passed you on the street. As the vehicle approaches, the pitch sounds higher; as it moves away, the pitch drops. The sound itself has not changed. What changed is how the waves reach you because the source is moving.

Moving blood cells do the same thing to ultrasound waves. When sound bounces off blood flowing toward the transducer, the returning echo shifts slightly in frequency one way. When blood flows away, it shifts the other way. The faster the flow, the bigger the shift. The ultrasound machine measures these tiny shifts and translates them into information about the direction and speed of blood flow.

Three ways the information is displayed

During a vascular exam, your technologist typically switches between several display modes:

1. Greyscale imaging. The familiar black-and-white picture shows the vessel’s shape, walls and any material within it.
2. Colour Doppler. Colour is layered over the greyscale image to show blood moving within the vessel. One colour generally represents flow toward the transducer and another represents flow away. Areas of unusual colour patterns can suggest turbulence.
3. Spectral Doppler. This produces a waveform graph showing the speed of blood over time, beat by beat. The shape of the waveform gives useful information about how the vessel is functioning.

You may also hear a whooshing, rhythmic sound during the exam. That is the Doppler signal converted into audio. It is perfectly normal and is one more way the technologist assesses flow.

What vascular ultrasound can help show

Vascular ultrasound is used to answer specific questions your doctor has about circulation. Depending on what has been requested, the exam can help identify:

• Blood clots in veins. A common reason for a venous ultrasound is to check for deep vein thrombosis, a clot in one of the deeper veins, often in the leg.
• Narrowing of arteries. Plaque buildup can narrow arteries and reduce blood flow. The carotid arteries in the neck and the arteries of the legs are frequently examined.
• Information related to stroke risk. Imaging of the carotid arteries gives your physician valuable information when assessing stroke risk.
• Vein valve function. In some exams, the technologist assesses whether blood in the leg veins flows in the right direction, which can be relevant to varicose veins and leg swelling.
• Changes over time. For people already being monitored for vascular disease, repeat scans can help their doctor track whether anything has changed.

An ultrasound provides information, not a diagnosis on its own. The images and measurements are interpreted and reported, and your referring doctor puts the findings together with your symptoms, history and other test results.

What ultrasound cannot do as easily

Like every imaging method, ultrasound has strengths and limits, and knowing them can help explain why your doctor might order more than one type of test.

• Depth and body shape. Sound waves weaken as they travel deeper. Vessels close to the skin, such as those in the neck and legs, are usually well suited to ultrasound. Vessels deep in the abdomen can be harder to see clearly in some people.
• Bone and air. Sound does not pass well through bone or gas. Areas hidden behind bone or bowel gas may be difficult to image.
• Operator skill. Ultrasound is a hands-on exam. The quality of the result depends partly on the skill of the technologist, which is why vascular studies are performed by trained, certified staff.
• A snapshot in time. An ultrasound shows what is happening on the day of the exam. If symptoms change afterwards, your doctor may decide to repeat it or order something different.

None of these limits make vascular ultrasound less valuable. They simply explain why it is often one step in an assessment rather than the only one.

Why a doctor might order one

There are many reasons your health-care provider might request a vascular ultrasound. Some of the more common include:

• swelling, pain, warmth or redness in one leg or arm
• leg pain or cramping that comes on with walking and eases with rest
• a sound heard through a stethoscope over an artery in the neck, sometimes called a bruit
• a history of brief stroke-like symptoms
• risk factors for vascular disease such as high blood pressure, diabetes, high cholesterol or a history of smoking
• monitoring after a previous finding or procedure
• visible varicose veins or skin changes on the lower legs

If you are not sure why your doctor ordered the test, it is completely reasonable to ask them before your appointment. Knowing the reason often makes the experience feel less uncertain.

Different vascular exams, different areas

“Vascular ultrasound” is an umbrella term. The exam you have depends on the question being asked.

Carotid ultrasound

The carotid arteries run up each side of the neck and supply blood to the brain. You lie on your back with your head turned slightly, and the transducer is moved along the side of your neck.

Venous ultrasound of the legs or arms

This exam looks at veins, often to check for a clot. The technologist moves the transducer along the length of the limb and may gently press on the vein at intervals. A healthy vein usually compresses under light pressure, while a vein containing a clot may not. You may be asked to change position or to briefly hold your breath at times.

Arterial ultrasound of the legs

When circulation in the legs is a concern, the arteries are examined along their length to look for narrowing.

What the appointment is like

At Rossland Diagnostic Clinic, vascular ultrasound is performed by certified technologists using high-precision equipment. While each exam is different, most follow a similar pattern:

• You will be asked to remove clothing or jewellery from the area being examined and may be given a gown.
• You lie on a padded exam bed, usually on your back, though position can change during the exam.
• Gel is applied, and the technologist moves the transducer over the skin, pausing to capture images and measurements.
• The room may be dimmed so the screen is easier to read.
• Some pressure may be applied, particularly during venous exams. Tell your technologist if anything is uncomfortable.

The length of the exam varies with the area being studied and whether one or both sides are examined.

Preparing for your exam

Preparation differs from one vascular study to another. Our team will give you any specific instructions when your appointment is confirmed. In general, it helps to wear comfortable, loose clothing, bring your health card and requisition, and arrive a little early so you are not rushed.

Results

Your technologist’s role is to capture clear, complete images and measurements. The findings are sent to your referring doctor, who is the right person to go over them with you, explain what they mean for you and discuss any next steps.

How it fits with other heart and circulation testing

Vascular ultrasound is one part of a broader picture. Your doctor may also order tests that look directly at the heart, such as an echocardiogram, which uses ultrasound to evaluate the heart’s structure, valves and blood flow. At our clinic, cardiac testing is offered through our cardiology team, Durham Cardiology. General abdominal, pelvic and musculoskeletal imaging is available through our ultrasound services.

Booking a vascular ultrasound in Ajax

If your doctor has given you a requisition for a vascular ultrasound, our clinic at 300 Rossland Road East in Ajax offers free parking and ground-floor access, which makes the visit easier for anyone with leg discomfort or limited mobility. Patients come to us from across Ajax, Pickering, Whitby and the wider Durham Region.

To arrange your exam, call 905-426-3111 or request an appointment online. Our team will confirm your appointment and let you know how to prepare.