What is a Doppler examination?
A Doppler test or Doppler ultrasound is a non-invasive diagnostic procedure that uses high frequency sound waves to examine the rate of blood flow in your blood vessels. The sound waves that are directed on the blood vessels bounce off the circulating blood cells and are recorded as the speed and direction of blood flow. The movement of the blood inside the vessel creates changes in the pitch of the reflected sound waves. When there is no change in pitch, it shows that there is no flow of blood, which could in turn indicate a blockage or abnormality in the blood vessel. Through this method, the Doppler ultrasound can determine reduced or blocked blood flow in your arteries and veins.
There are 3 types of Doppler ultrasound:
- Duplex Doppler: The technique is a standard ultrasound that uses a computer to convert the sound waves into a graph. It produces a picture of the blood vessels and surrounding organs.
- Bedside or continuous wave Doppler: This is a portable machine, generally used at the bedside in the hospital.
- Color Doppler: It involves the use of a computer to convert Doppler sounds into colored images of the blood vessel.
What are the indications for a Doppler examination?
Doppler ultrasound is used as a diagnostic tool for the following:
- Presence of blood clots
- Narrowed or blocked blood vessels
- Atherosclerosis or plaque (deposits of cholesterol and calcium) formation in blood vessels
- Aneurysms (bulging arteries)
- Leg pain and intermittent claudication (muscle cramp and aching)
- Assess blood flow after a stroke
- Varicose veins
- Blood flow to a transplanted liver or kidney
- Map blood vessels that could be used as grafts
- Guide certain treatment procedures
- Monitor blood flow after blood vessel surgery
- Heart valve defects
- Congenital heart disease
How is a Doppler examination performed?
Before a Doppler examination, you may be advised to quit smoking since the nicotine found in cigarettes may cause constriction of arteries in the extremities. This can alter the results of the Doppler examination.
During a Doppler examination, you will be connected to a blood pressure machine and your blood pressure is continuously monitored. Your doctor will apply a water-soluble gel on a transducer (hand-held probe) and on your skin over the region to be tested. The transducer is then gently moved over the gel. The transducer transmits and receives the reflected sound waves, which are amplified and recorded. The reflected sound waves are then processed by a computer to create graphs or images that depict the movement of the blood. This test takes around 30-60 minutes. Once completed, the gel will be cleaned from your skin.
What are the advantages of a Doppler examination over other diagnostic procedures?
A Doppler examination is a safe and non-invasive procedure, which can be performed as an alternative to minimally invasive procedures such as arteriography and venography, which require small incisions to inject a contrast dye into the arteries and veins in order to detect abnormalities.
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