Doppler sonography, or Doppler ultrasound, is a medical imaging technique that uses ultrasound enhanced by the Doppler effect. The Doppler effect generally uses a change in the pitch of sound waves that are measured by an ultrasound-receiving device such as a transducer. Colored Doppler images often provide helpful information about the flow and movement of blood and inner areas of the body. This technique is commonly used during pregnancy to provide detailed images of a developing unborn baby. Other uses for Doppler sonography may include visual examinations of tendons, joints and muscles as well as internal organs.
Pregnant women may undergo an ultrasound for several reasons such as measurement of blood flow through the umbilical cord as well as evaluation of the heart or brain of the unborn baby. This test usually shows the size of a developing fetus and may provide information about the health of the fetus, such as the amount of oxygen received. Physicians may identify health conditions in some pregnant mothers, such as sickle cell anemia or preeclampsia, with the aid of this test.
Some doctors have patients undergo Doppler sonography to investigate a number of medical conditions. Patients with leg pain may have intermittent claudication and atherosclerosis that can appear on a Doppler sonography image in some instances. Varicose veins and other abnormalities of blood vessels can be investigated with this form of ultrasound. Blood clots and blood flow blockages may be identified with Doppler sonography in some cases. Some physicians use this form of ultrasound to provide images that guide their work during surgical procedures such as a blood vessel ablation.
A patient usually lies on his back or side during an ultrasound. Medical professionals normally apply a special Doppler gel to the skin near an area where images are desired. A transducer is typically placed against the gel-covered skin and moved around to get Doppler sonography images from several desired angles. Most Doppler ultrasound tests are completed in 30 to 60 minutes. Doctors may recommend that patients not wear jewelry during a test to reduce the chance of image distortion.
In some instances, patients have unreliable results from a Doppler sonography due to several factors. Patients who do not remain still during the procedure while images are being recorded may cause images to become distorted. In some cases, bones in the body can block the ultrasound signals used during the test. Reliable ultrasound images may be more difficult to obtain in obese individuals, and irregular heart rhythms may cause abnormal images of blood vessels.
What is Doppler sonography?
This technique uses reflected sound waves to measure blood flow in different parts of your baby's body. (The machine used to listen to your baby's heartbeat throughout pregnancy – known as a handheld Doppler – also uses these sound waves.) Doppler sonography helps your caregiver assess your baby's health and can be done at the same time as an ultrasound.
Most modern ultrasound machines have a Doppler function. Once your sonographer locates a specific blood vessel that she wants to evaluate (one of the arteries in the umbilical cord, for instance), she presses a button to turn on the Doppler function. Blue or red highlights on the screen signal the characteristics of the blood flow, which the machine then analyzes. All of this takes just a few minutes during your ultrasound. In what situations is Doppler sonography used?
Doppler sonography is most often used during the third trimester in women with high-risk pregnancies, including those who have low amniotic fluid levels, Rh-incompatibility, or twins sharing the same placenta, or whose babies aren't growing as they should.
Your practitioner can use Doppler sonography to literally see the flow of blood from the placenta to your baby, or in your baby's body itself. (This can be helpful if, for example, your placenta isn't delivering enough blood to your baby or if your baby has developed anemia, which thins the blood.) This information will help your practitioner decide whether your baby should be delivered early or if other medical measures are needed to protect his health.
Doppler sonography can also be used during a transvaginal ultrasound for gynecological reasons. It may be used to check on an ovarian cyst, for example, or to help diagnose an ectopic pregnancy.