What is ultrasound?
Ultrasound, also called sonography, is a method of “seeing” inside the human body through the use of high-frequency sound waves. The sound waves are recorded and displayed as a real-time visual image. No radiation is involved in ultrasound imaging. Ultrasound is a useful way of examining many of the body’s internal organs, including the heart, liver, gallbladder, spleen, pancreas, kidneys, and bladder. Because ultrasound images are captured in real-time, they can show movement of internal tissues and organs, and enable physicians to see blood flow and heart valve functions. This can help to diagnose a variety of heart conditions and to assess damage after a heart attack or other illness.
What are some common uses of ultrasound?
Millions of expectant parents have seen the first “picture” of their unborn child with pelvic ultrasound examinations of the uterus and fetus. Ultrasound imaging is used extensively for evaluating pelvic and abdominal organs, and blood vessels, and can help a clinician determine the source of pain, swelling, or infection in many parts of the body. Because ultrasound provides real time images, it can also be used to guide procedures such as needle biopsies, in which a needle is used to sample cells from an organ for laboratory testing. Ultrasound can also be used to image the breasts and to guide biopsy of breast cancer.
Doppler ultrasound is a special technique used to examine blood flow. Doppler images can help the physician to see and evaluate blockages to blood flow, such as clots; build-up of plaque inside blood vessels and congenital vascular malformations.
How does ultrasound work?
As the sound passes through the body, echoes are produced that can be used to identify how far away an object is, how large it is, and how uniform it is. The ultrasound transducer functions as both a generator of sound (like a speaker) and a detector of sound (like a microphone). When the transducer is pressed against the skin, it directs inaudible, high-frequency sound waves into the body. As the sound echoes from the body’s fluids and tissues, the transducer records tiny changes in the pitch and direction of the sound. These echoes are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor.
What to Expect
Typically, you are positioned on your back on the examination table. A clear gel is applied to your body in the area to be examined, to help the transducer make secure contact with the skin. The sound waves produced by the transducer cannot penetrate air, so the gel helps eliminate air pockets between the transducer and the skin.
The technologist or physician will press the transducer firmly against your skin and sweep it back and forth to image the area of interest. You may experience some discomfort from pressure as the technologist guides the transducer over your abdomen, especially if you are required to have a full bladder. The examination usually takes less than 30 minutes.
You should wear comfortable, loose-fitting clothing for your ultrasound exam. You may need to remove all clothing and jewelry in the area to be examined. You may be asked to wear a gown during the procedure.
Other preparation depends on the type of examination you will have. For some scans your doctor may instruct you not to eat or drink for as many as 12 hours before your appointment. For others you may be asked to drink up to six glasses of water two hours prior to your exam and avoid urinating so that your bladder is full when the scan begins.