This test uses high-frequency ultrasound to visualize the anatomy and blood flow in legs. This is the same type of instrument used to examine unborn babies, the size or structure of abdominal organs, such as the gall bladder, or to evaluate the blood flow in the neck and the carotid arteries. The name "duplex" comes from combining the two meanings:
- the conversion of ultrasound signals into sounds that you can hear and
- pictures that you can see.
The Doppler part of the test works by sending a high-frequency sound (ultrasound) wave through a transmitting gel into the body. This sound wave bounces off the layers of the body, such as muscle, bone, blood vessels, and various organs. Each type of body tissue absorbs ultrasound signals differently. For example, if you took a tennis ball and bounced it on different surfaces, it would bounce differently. It bounces high on a hard surface like cement, yet barely at all on a soft surface such as grass. In a similar manner that bats and submarines use sound to see were they are going, your vascular specialist uses ultrasound to see images of your body.
How is the exam given?You will be asked to lie on your back. Water-based gel will be placed along segments on your legs. The pencil shaped ultrasound probe will be placed in the gel to display a segment of your artery. The doctor or technologist will move the probe slowly up and down the arteries to see and hear the blood flow. Your legs may be repositioned to allow a better view of the artery.
What will the results mean?These images help to determine if you have cholesterol plaque, narrowed arteries or blockages in the blood vessels of your legs. In addition, most duplex imaging systems also show the direction of your blood flow in color. This information allows the vascular specialist to determine if the blood is flowing away (arterial) or toward (venous) your heart.