THE MEDICAL IMAGING EXPERIENCE
INFORMATION FOR THE PATIENT
CAROTID DUPLEX DOPPLER FLOW EXAM (CDF)

WHAT IS IT?
A Carotid Duplex Doppler Flow exam is an ultrasound procedure to evaluate the flow of blood in the arteries in your neck (Carotid Arteries). This procedure helps determine the amount of blood flow to your brain by looking for artery disease (plaque) that inhibits the blood flow.

Ultrasound procedures involve the use of very high frequency sound waves that cannot be heard by the human ear. The sound waves are sent into the blood vessel using a hand held instrument called a transducer. The variations in blood flow in a blood vessel reflect sound waves differently. Some of the sound waves reflect back to the transducer much like your voice echoes back to you in an empty building. The reflected sound waves are received by the transducer and sent to a computer to be processed.

WHAT WILL HAPPEN TO ME?
The sonographer (the person who operates the ultrasound machine) will assist you as you lie on your back on a padded table. The sonographer will feel for pulses on your neck, face and arms and take blood pressure readings from both arms. Frequently, the sonographer uses a stethoscope to listen for blood flow in the artery. A gel will be spread on your neck. The gel improves the ability to send and receive the sound waves between the transducer and your body. The sonographer moves the transducer over your neck while frequently changing the position and angle of the transducer. This action guides the sound waves to specific parts of the blood vessels so that pictures can be taken. The sonographer may ask you to change positions periodically.

HOW LONG WILL THIS TEST TAKE?
This ultrasound procedure usually takes about 45 minutes to complete. The time can vary depending on the difficulty in locating the blood vessels and then recording the various blood flow patterns.

WHAT WILL I FEEL -- WILL IT HURT?
Usually the ultrasound room lights are turned down to darken the room. This helps the sonographer to see the video screen better. Ultrasound procedures are not painful. You will feel some pressure as the sonographer presses the transducer against your neck. During part of the exam, you will hear a loud "swishing" sound as the ultrasound machine tracks the direction and speed of blood flow within the blood vessels.

WHAT WILL THE TEST SHOW?
Ultrasound can see the blood flow in the arteries that supply blood to the brain. If plaque has collected on the internal wall of the artery and restricted the blood flow or other obstructions limit the blood flow in the artery this can be identified with this exam.

HOW DO I GET READY?
You should remove any necklaces from around your neck to prevent interference. Wear loose fitting clothing around your neck. You should go to the bathroom just before your exam so that you are as comfortable as possible during the exam.

Reviewed: October 2005