Doppler ultrasound is based upon the Doppler Effect. When the object reflecting the sound waves is moving, it changes the frequency of the echoes. It creates higher frequency when it moves towards the probe and lower frequency when moving away from the probe. The change in the frequency depends on how fast the object is moving. This is a special technique mainly used to examine blood flow. Problems in the veins and arteries are detected by Doppler ultrasound. Doppler ultrasound is also used to measure the blood flow through the heart. The direction of the blood flow is shown in different colors on the ultrasound machine screen. The Doppler images help the physician to see and evaluate blockages to blood flow, such as clots, narrowing of vessels, which may be caused by plaque and such diseases. Tumors and congenital malformation are also detected by Doppler ultrasound.
An echocardiogram is a diagnostic test that gives the doctor an idea of how the heart appears in motion. An echo uses ultrasound waves to pick up echoes from different parts of your heart. An echocardiogram throws light on the size of the heart and the condition of the heart valves. The pumping capacity of the heart is determined with an echocardiogram. Any damage to heart muscles or valves can be diagnosed with an echocardiogram. An echocardiogram is helpful in detecting any structural problems of the heart, its chambers or blood vessels surrounding it. An echocardiogram is used to detect any blood clots within the heart. This diagnostic test is used to check for causes of irregular heartbeats, enlarged heart or heart murmurs. The functioning of the heart after an attack can be checked with an echocardiogram.
Trans thoracic echocardiogram is the standard cardiogram where the doctor monitors sound wave echoes that bounce off the heart and other internal structures.
Doppler echocardiogram is based on Doppler signals that change pitch when they bounce off the heart and blood vessels. This feature is often part of other cardiogram procedures.
Stress echocardiogram is taken when a patient is undergoing a treadmill stress test.
Trans esophageal echocardiogram involves passing a probe through the throat into the chest wall. The transducer then shows clear images of the heart. This type of echocardiogram can be uncomfortable and is often performed under sedative. Trans esophageal echocardiogram is also used during surgery to monitor the heart function. Abnormal blood flow between the heart's chambers can be detected.
During the early days of pregnancy, amniocentesis is carried out on pregnant woman to find out if the developing fetus is free from certain abnormalities. This procedure involves certain invasive methods like inserting a hollow needle into the uterus of the woman through her abdominal wall to withdraw a sample of amniotic fluid that surrounds the fetus. Using ultrasound, the location of the fetus floating in the amniotic fluid is determined. The abdominal skin surrounding the area is cleaned. The procedure may be conducted either by injecting a local anesthetic in that area, or by just applying a tropical anesthetic around the area through which the needle is to be inserted. About 1 cc per week of gestation of the fetus is taken out from the amniotic fluid.
This procedure is used as a tool which can detect chromosomal disorders like Downs Syndrome and many rare metabolic disorders which are normally inherited. Some structural defects like spina bifida and anencephaly can be detected using this test. This procedure is normally carried out for women over the age of thirty five. It is recommended for women who had undergone a triple screen blood test during pregnancy and for those who have a family history of birth defects or some inherited metabolic disorders. This procedure may be conducted even in later stages of pregnancy to detect suspected problems like Rh incompatibility or infection. This test is also used to determine lung maturity of the infant in the last trimester.
A cell culture is done with the fetal cells taken out during the procedure and the analysis of the DNA is conducted to detect chromosomal abnormalities. It may take up to a month for the results to arrive. This is rated as a highly accurate procedure.
After the withdrawal of the amniotic fluid which takes only a few minutes, the pregnant woman is advised to be in bed for several hours, though the entire procedure will last for about 45 minutes. Doctors check the heart beat of fetus to ensure that it is normal. It is wise to call the health care provider, if the woman experiences fever, bleeding or leakage of amniotic fluid for a long time. Though the chances of infection or injury to the fetus are not ruled out, they are quite rare. There is also a slight chance of miscarriage, but the percentage is negligible. During later stages of pregnancy, a Doppler ultrasound is safer than amniocentesis because it is non-invasive. Anemia in the fetus can easily be detected using ultrasound by measuring the velocity of the blood flow in the middle cerebral artery.
Bibliography / Reference
Collection of Pages - Last revised Date: August 23, 2017