Duplex Ultrasound LAB Investigations

Duplex Ultrasound

Vascular assessment requires images and flow, two forms of ultrasound. Because Colour imaging is now used routinely, in addition, the study is often defined as Triplex Ultrasound.

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What is Vascular Ultrasound?

Ultrasound imaging, also called ultrasound scanning or sonography, involves exposing part of the body to high-frequency sound waves to produce sound echo pictures of the inside of the body. Ultrasound examinations do not use ionizing radiation (as used in x-rays).

 

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.

Ultrasound is not a simple procedure

and despite the wide ranging services offering tests the results are subjective and depend enormously on the skills and understanding of the operator. In the vascular service the operator has to learn to fine tune the machine to get the best results, they must have an excellent working knowlege of the anatomy in the area of the body that is being examined as well as a thorough up to date understanding of the pathological processes likely to be found, the possible therapies that might be offered in addition to understanding the demands that their endovascular/vascular surgeon requires to plan treatment. I believe Vascular Ultrasound should be carried out by specialist Ultrasonographers under guidance of skilled Vascular Specialists to achieve the best outcomes and appropriate assessment of the test.

The tests should be clinically driven.

Venous studies should be comprehensive. We see massive waste when tests for DVT are requested, found negative, but no functional studies are carried out to exclude or prove other major venous problems that could be causing the symptoms and findings. Instead of guidelines being used for the minimal study required  they are generally used to limit the investigation. 

Basic ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions, contrast materials can be given intravenously to enhance images and increase the sensitivity of flow investigations. Microbubbles can be induced in Normal Saline by agitation and when injected this can very sensitvely define Right to Left Shunts in the heart. 

Vascular ultrasound provides pictures of the body's veins and arteries and Doppler ultrasound study is  part of a vascular ultrasound examination as it can allow precise flow measurements in individual sites of  the body's major arteries and veins in the abdomen, arms, legs and neck. Sonography is a useful way of evaluating the body's circulatory system.

Specialist Vascular Ultrasound is performed to:

  • Help monitor the blood flow to organs and tissues throughout the body.

  • Locate and identify blockages (stenosis) and abnormalities like plaque or emboli and help plan for their effective treatment.

  • Detect blood clots (deep venous thrombosis (DVT) in the major veins of the legs or arms.

  • Examine the structure of the thrombus and attempt ageing of the clot to assess likelihood that Lysis might be effective 

  • Determine whether a patient is a good candidate for a procedure such as angioplasty.

  • Evaluate the success of procedures that graft or bypass blood vessels.

  • Determine if there is an enlarged artery (aneurysm).

  • Determine the source and severity of varicose veins.

  • Determine the cause of DVT, Paget-Schroetter, Pop Vein Compression Syndrome and explore for some cancers.

  • Using Echo check for heart failure in the chronic swollen legs

  • Attempt to define the quality and instability of plaque in critical stenoses, e.g. the carotids

  • Doppler ultrasound images can help the physician to see and evaluate:

  • blockages to blood flow (such as clots).

  • narrowing of vessels (which may be caused by plaque).

  • tumors and congenital vascular malformation.


How should I prepare?

You should wear comfortable, loose-fitting clothing for your ultrasound exam. You may need to remove all clothing and jewelry in the area to be examined. You may be asked to wear a gown during the procedure.

If your abdominal vessels are being examined, unless the examination is performed on an urgent basis, it is often best to fast before the procedure.

What does the equipment look like?

Ultrasound scanners consist of a console containing a computer and electronics, a video display screen and a transducer that is used to do the scanning. The transducer is a small hand-held device that resembles a microphone, attached to the scanner by a cord. 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. 

Diagnostics and Ultrasound

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 (strength), frequency and time it takes for the sound signal to return from the area of the patient being examined to the transducer and the type of body structure the sound travels through.

How does the procedure work?

Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships, fishermen and the weather service. 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 and its size, shape and consistency (whether the object is solid, filled with fluid, or both).

In medicine, ultrasound is used to detect changes in appearance of organs, tissues, and vessels or detect abnormal masses, such as tumors.

In an ultrasound examination, a transducer both sends the sound waves and receives/records the echoing waves. When the transducer is pressed against the skin, it directs small pulses of inaudible, high-frequency sound waves into the body. As the sound waves bounce off of 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. One or more frames of the moving pictures are typically captured as still images. Small loops of the moving “real time” images may also be saved.

Doppler ultrasound, a special application of ultrasound, measures the direction and speed of blood cells as they move through vessels. The movement of blood cells causes a change in pitch of the reflected sound waves (called the Doppler effect). A computer collects and processes the sounds and creates graphs or color pictures that represent the flow of blood through the blood vessels.

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 presses the transducer firmly against the skin in various locations, sweeping over the area of interest or angling the sound beam from a farther location to better see an area of concern.

Doppler sonography is performed using the same transducer.

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

This ultrasound examination is usually completed within 30 to 45 minutes.

Occasionally, complex examinations may take longer.

What will I experience during and after the procedure?

Most ultrasound examinations are painless, fast and easy.

After you are positioned on the examination table, our specialist sonographer or consultant will apply some warm water-based gel on your skin and then place the transducer firmly against your body, moving it back and forth over the area of interest until the desired images are captured. 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.

If a Doppler ultrasound study is performed, you may actually hear pulse-like sounds that change in pitch as the blood flow is monitored and measured.

Once the imaging is complete, the gel will be wiped off your skin.

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

Who interprets the results and how do I get them?

Dr Grosser or his assistant, will analyze the images and discuss the results with you ,plan further management which will be discussed in detail and provide you with a signed report for your records and for your primary care physician or the practitioner who referred you for the exam.

Follow-up examinations are often necessary, and your doctor will explain the exact reason why another exam is requested. Sometimes a follow-up exam is done because a suspicious or questionable finding needs clarification with additional views or a special imaging technique. A follow-up examination maybe necessary so that any change in a known abnormality can be detected over time. Follow-up examinations are sometimes the best way to see if treatment is working or if an abnormality is stable over time.

 

Risks?

For standard diagnostic ultrasound there are no known harmful effects on humans.

What are the limitations of Vascular Ultrasound?

  • Vessels deep in the body are harder to see than superficial vessels. Specialized equipment or other tests such as CT or MRI may be necessary to properly visualize them.

  • Smaller vessels are more difficult to image and evaluate than larger vessels.

  • Calcifications that occur as a result of atherosclerosis may obstruct the ultrasound beam.

  • Sometimes ultrasound cannot differentiate between a blood vessel that is closed versus one that is nearly closed. Even if there is a very small remaining opening, the weak blood flow produces a sometimes undetectable signal.

Ultrasound is not a simple procedure and despite the wide ranging services offering tests the results are subjective and depend enormously on the skills and understanding of the operator. In the vascular service the operator has to learn to fine tune the machine to get the best results, they must have an excellent working knowlege of the anatomy in the area of the body that is being examined as well as a thorough up to date understanding of the pathological processes likely to be found, the possible therapies that might be offered in addition to understanding the demands that their endovascular/vascular surgeon requires to plan treatment. I believe Vascular Ultrasound should be carried out by specialist Ultrasonographers under guidance of skilled Vascular Specialists to achieve the best outcomes and appropriate assessment of the test.