Alternative names: Ultrasonography, Sonography, Echocardiography, Doppler Echocardiography,
Ultrasound is a safe and painless diagnostic medical procedure used to produce images of structures within the human body, using high-frequency (ultrasonic) sound waves. Ultrasound can display the movement and actual function of the body's organs and blood vessels.
The images produced by ultrasound are not as precise as those obtained through a CAT scan or MRI, but it is quick, relatively inexpensive and safe. The main limitation of ultrasound is that it does not reflect clearly from bone or air. Other imaging techniques are used for areas such as the lungs and bones.
Ultrasound technology was originally developed as sonar to track submarines during World War I. It was first used medically in the 1950s.
During the ultrasound examination, a machine called a transducer aims ultrasonic waves at a specific area of the body (generally the abdomen), detects the returning echoes, and feeds this data to the scanner. As the waves travel through body tissue, their echoes indicate variations in tissue density, such as the border between two different organs. From the position and intensity of the echoes, the ultrasound device creates images of the inside of the body in real time.
Ultrasound waves pass easily through fluids and soft tissues, making it especially useful for examining fluid-filled organs and soft organs. Ultrasound waves can not penetrate bone or gas, so it is not very useful for examining regions surrounded by bone, or areas that contain gas or air. Ultrasound has, however, been used to examine most parts of the body.
From these images, the ultrasound technician can take accurate measurements, produce static snapshots and annotate them for review by a doctor. A summary of findings is generally included with the annotated still images.
Obstetric ultrasound is most commonly used between the 16th and 18th weeks of pregnancy to examine the fetus in order to ascertain size, position, or abnormalities. If the date of conception is known, the scan can demonstrate whether or not the fetus is of expected size. If the date of conception is unknown, or the mother is uncertain, ultrasound of fetal size can help establish the accurate date of conception. It can also reveal multiple pregnancy (twins or triplets for example), congenital heart disease, the position of the placenta, general health of the fetus, ectopic pregnancy, risk of miscarriage, or fetal death.
Ultrasound is used to provide images of the following:
Ultrasound is also used to guide certain procedures, such as needle biopsies, the introduction of tubes for drainage, and intrauterine corrective surgery. Ultrasound provides a real time, moving image which is valuable in helping to guide the needle accurately to a specific spot.
Echocardiography is a specialized type of ultrasound that is used to look at the action and function of the heart, and detect congenital heart disease, enlargement of or damage to the heart muscle, aneurysms, blood clots, swelling or inflammation.
Doppler Echocardiography is a more recent ultrasound technique that measures the flow velocity of blood as it passes through the heart. It is used to locate malfunctioning valves (aortic stenosis – narrowing of the aortic valve opening) or mitral insufficiency (failure of the mitral valve to close properly) and in assessing patients with congenital heart disease.
Depending on the type of ultrasound exam, you may be asked not to eat or drink for up to 6 hours prior, or drink up to six glasses of water two hours prior and avoid urinating. This will ensure a full bladder when the exam begins. Detailed instructions will be given by your physician.
Ultrasound is universally accepted as being safer than other imaging methods such as CAT scans or X-rays which use ionizing radiation. There are no known harmful effects on humans associated with ultrasound imaging.
Ultrasound, the diagnostic method most frequently used to detect gallstones, is a simple, rapid, and noninvasive imaging technique. Ultrasound detects gallstones as small as two millimeters in diameter with an accuracy of 90% to 95%. The patient must not eat for six or more hours before the test, which takes only about 15 minutes. During the same procedure, the physician can check the liver, bile ducts, and pancreas and quickly scan the gallbladder wall for thickening (characteristic of cholecystitis). There are many other, more sophisticated tests, that may be suggested for further evaluation of the problem.
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