Doppler Ultrasound

What is Doppler Ultrasound Imaging?

Ultrasound is safe and painless, and produces pictures of the inside of the body using sound waves. Ultrasound imaging, also called ultrasound scanning or sonography.

Ultrasound is a noninvasive medical test that helps physicians diagnose and treat medical conditions. It uses sound waves to produce pictures of the body's veins.

Because ultrasound images are captured in real-time, they can show the structure and movement of the body's internal organs, as well as blood flowing through blood vessels.

Doppler Ultrasound is a special type of ultrasound that can sense movement of tissues in the body, particularly blood, using the principle of the Doppler effect. Blood moving away from the ultrasound sensor lengthens the returning ultrasound wave and blood moving towards the sensor shortens the ultrasound wave. A computer collects and processes the sounds and creates graphs or colour pictures that represent the flow of blood through the blood vessels.

Why is Doppler Ultrasound Required?

Doppler ultrasound is a special ultrasound technique that allows the physician to see and evaluate blood flow through arteries and veins.

Venous ultrasound provides pictures of the veins throughout the body. Doppler Vascular Ultrasound is commonly used to search for blood clots, especially in the veins of the leg – a condition often referred to as deep vein thrombosis.

These clots may break off and pass into the lungs, where they can cause a dangerous condition called pulmonary embolism. If the blood clot in the leg is found early enough, treatment can be started to prevent it from passing to the lung.

Where is Ultrasound Used?

The areas of the body that can be examined using doppler ultrasound include:

Abdomen, looking at the vessels to the organs
Arms,
Legs,
Neck and/or
Brain (in infants and children)
Within various body organs such as the liver or kidneys.

What Can Ultrasound Diagnose?

Doppler ultrasound images can help the doctor to see and evaluate:

mass lesions
sites of inflammation and swelling to assess for infection
look for foreign bodies such as pieces of metal or wood under the skin
blockages to blood flow (such as clots)
narrowing of vessels
tumors and congenital vascular malformations
less than normal or absent blood flow to various organs
greater than normal blood flow to different areas which is sometimes seen in infections

Further Vascular Ultrasound can help:

Understand the cause of long-standing leg swelling
Damage to the valves that keep blood flowing back to the heart in the right direction may be damaged
in the placement of a needle or catheter into a vein. Sonography can help locate the exact site of the vein and avoid complications, such as bleeding or damage to a nearby nerve or artery.
map out the veins in the leg or arm so that pieces of vein may be removed and used to bypass a narrowed or blocked blood vessel. An example is using pieces of vein from the leg to surgically bypass narrowed heart (coronary) arteries.
examine a blood vessel graft used for dialysis if it is not working as expected; for example, the graft may be narrowed or blocked.

Ultrasound Diagnosis & Children

In children, ultrasound is used to:

evaluate a connection between an artery and a vein which can be seen in congenital vascular
malformations (arteriovenous malformations or fistula) and in dialysis fistula.

What are the benefits of Ultrasound?

The Benefits of Ultrasound scanning (noninvasive, no needles or injections), include

easy-to-use and less expensive than other imaging methods.
extremely safe and does not use any ionizing radiation.
gives a clear picture of soft tissues that do not show up well on x-ray images.
helps to detect blood clots in the veins of the legs before they become dislodged and pass to the lungs. It can also show the movement of blood within blood vessels.
In many cases it does not require injecting contrast material into a vein, venous ultrasound is accurate for detecting blood clots in the veins of the thigh down to the knee.

How does Ultrasound Work?

Doppler Vascular Ultrasound involves the use of

a small transducer (probe)
A console containing a computer and electronics,
a video display screen
ultrasound gel placed directly on the skin to allow the sound waves to best travel from the transducer to the examined area within the body and then back again

High-frequency sound waves are transmitted from the probe through the gel into the body.

The transducer is a small hand-held device that resembles a microphone, attached to the scanner by a cord. It collects the sounds that bounce back and a computer then uses those sound waves to create an image.

Some exams may use different transducers (with different capabilities) during a single exam. The transducer sends out inaudible, high—frequency sound waves into the body and then listens for the returning echoes from the tissues in the body. The principles are similar to sonar used by boats and submarines.

The ultrasound image is immediately visible on a video display screen that looks like a computer or television monitor. The image is created based on the

amplitude (loudness),
frequency (pitch) and
time it takes for the ultrasound signal to return from the area within the patient that is being examined to the transducer (the device used to examine the patient),

as well as the type of body structure and composition of body tissue through which the sound travels.

How Does The Procedure Work?

Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships and fishermen. When a sound wave strikes an object, it bounces back, or echoes. By measuring these echo waves, it is possible to determine how far away the object is as well as the object's size, shape and consistency (whether the object is solid or filled with fluid).

As the sound waves bounce off internal organs, fluids and tissues, the sensitive microphone in the transducer records tiny changes in the sound's pitch and direction. These signature waves are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor.

The Ultrasound Imaging Results

A radiologist will analyze the images and send a signed report to your primary care physician, or to the physician or other healthcare provider who requested the exam.

Usually, the referring physician or health care provider will share the results with you. In some cases, the radiologist may discuss results with you at the conclusion of your examination.

What if Follow Up is Required

Follow-up examinations may be necessary, and your doctor will explain the exact reason why another exam is requested. Sometimes a follow-up exam is done because a potential abnormality needs further evaluation with additional views or a special imaging technique.

A follow-up examination may also be necessary so that any change in a known abnormality can be monitored over time. Follow-up examinations are sometimes the best way to see if treatment is working or if a finding is stable or changed over time.

Preparation for Ultrasound Imaging

If the veins in your abdomen are to be examined, you may be asked not to eat or drink anything but water for six to eight hours beforehand.

Otherwise, little or no special preparation is required for this procedure

On The Day of the Ultrasound Imaging

Leave jewelry at home and wear loose, comfortable clothing.

During Ultrasound Imaging

This ultrasound examination is usually completed within 30 to 45 minutes. More complex exams may take a longer period of time.

You may be asked to wear a gown.

Most often you will be positioned lying face-up on an examination table that can be tilted or moved. Patients may be turned to either side to improve the quality of the images.
A clear water-based gel is applied to the area of the body being studied to help the transducer make secure contact with the body and eliminate air pockets between the transducer and the skin that can block the sound waves from passing into your body.
The sonographer (ultrasound technologist) or radiologist then places the transducer on the skin in various locations, sweeping over the area of interest or angling the sound beam from a different location to better see an area of concern.
Doppler sonography is performed using the same transducer.
You may actually hear pulse-like sounds that change in pitch as the blood flow is monitored and measured.

There is usually no discomfort from pressure as the transducer is pressed against the area being examined.
If scanning is performed over an area of tenderness, you may feel pressure or minor pain from the transducer.

After the Ultrasound Imaging

Once the imaging is complete, the clear ultrasound gel will be wiped off your skin. Any portions that are not wiped off will dry to a powder. The ultrasound gel does not stain or discolor clothing.

When the examination is complete, you may be asked to dress and wait while the ultrasound images are reviewed.

After an ultrasound examination, you should be able to resume your normal activities immediately.

Risks with Doppler Vascular Ultrasound

Ultrasound examinations do not use ionizing radiation (as used in x-rays), thus there is no radiation exposure to the patient. Ultrasound examinations has no known harmful effects.

Occasionally, an ultrasound exam may be temporarily uncomfortable, but it should not be painful.