Ultrasound makes waves - includes related articles

FDA Consumer, Dec, 1991 by Margie Patlak

Ultrasound became a household word in the 1970s, when it was readily embraced by obstetricians, who used the high-frequency sound to peer into the womb. Many mothers "saw" their children before they were even born, thanks to ultrasound, which often suggested whether to buy pink or blue baby outfits, among other things.

With recent improvements in ultrasound's image quality and ease of use, this technology has found its way into almost every branch of medicine. Physicians now use ultrasound to detect tumors, aneurysms, blood clots, detached retinas, heart abnormalities, and kidney stones. Ultrasound can also map plaque buildup on arteries, and assess if a transplanted organ is being rejected.

On the treatment front, ultrasound is being used to treat glaucoma, speed the healing of bone fractures, and relieve the pain and stiffness of arthritis and other inflammatory disorders. Ultrasound also can aid surgery, cancer therapy, in vitro fertilization, and several dental procedures.

Seeing with Sound

Ultrasound's widespread popularity in the diagnostic arena stems from its relatively low cost, ease of use, and record of safety compared with other tools for diagnosing various disorders. Ultrasound also fares better than many imaging devices when it comes to picturing soft tissues in the body. It can also provide instant displays of moving structures and can offer other information on the functioning of an organ.

One way doctors use ultrasound to get the inside scoop on their patients' bodies is with a procedure known as pulse-echo imaging. During this procedure, a microphone-like device, known as a transducer, is moved across the skin over the part of the body the doctor wishes to view. The transducer emits sound waves (ultrasound) at a frequency too high to be heard by people.

When these waves bounce off various tissues and organs on their journey through the body, they generate distinctive echoes that are conveyed to a computer. The computer translates the timing and strength of these echoes into an image of the internal organs or tissues targeted by the ultrasound beam.

The ultrasound image (sonogram) is usually viewed on a television screen. When rapid pulses of ultrasound are used, a "movie" of a moving structure, such as a fetus or beating heart, can be seen.

There is no pain involved in pulse-echo imaging, although there may be some discomfort in procedures such as a pelvic sonogram, which requires the patient to maintain a full bladder while the womb (uterus) is imaged. The patient lies on an examination table for the procedure, which takes anywhere from five minutes for a pelvic sonogram to an hour for an ultrasonic exam of the heart. A gel is put on the patient's skin where the transducer makes contact. This gel improves the penetration of ultrasound waves.

A Womb with a View

Obstetricians frequently use pulse-echo ultrasound imaging to "see" what's happening inside the uterus. It can give valuable information, including:

* the size, number or age of fetuses in the womb. (Age is accurately assessed by measuring the length of the fetus or by measuring its thigh bone length and head circumference.)

* the presence of some types of birth defects

* location of the fetus or placenta (useful in the delivery of breech babies or during amniocentesis)

* fetal movement, breathing and heartbeat

* amount of amniotic fluid in the uterus (which helps in the assessment of fetal health).

Although most current studies do not indicate health risks to the unborn child from ultrasound imaging, more research needs to be done to determine this with certainty. Ultrasound imaging employs a different kind of radiation than x-rays, which clearly can harm the fetus. However, ultrasound can generate heat, microscopic bubbles, or vibrations, which could possibly affect fetal development.

An FDA panel, consequently, has recommended that ultrasound imaging not be done on pregnant women unless there is a specific medical reason such as vaginal bleeding, signs that the fetus is not growing properly, or a family history of congenital abnormalities. Ultrasound imaging should not be used, for example, just to get a glimpse of a fetus or to determine its sex.

Probing Lumps and Bumps

Pulse-echo ultrasound imaging has many other uses as well. Because it's an excellent tool for sizing up organs and spying any internal lumps or bumps, doctors often use ultrasound imaging to probe tissues for tumors, cysts or abscesses. Ultrasound is one of the safest tools doctors have for this purpose.

Unlike x-rays, sonograms can reveal not only whether there is a lump within a part of the body, such as the ovaries, but if that lump is likely to be a benign cyst or a solid tumor. Ultrasound is able to make this distinction, because a fluid-filled cyst has a different "sound signature" than a solid mass.

If a needle biopsy is warranted, ultrasound imaging can show doctors where to insert the needle to extract cells from abnormal tissue. Such needle biopsies can eliminate the need for surgery.