Ultrasound (or sonogram) technology allows doctors to "see" inside a patientwithout resorting to surgery. A transmitter sends high-frequency sound wavesinto the body, where they bounce off the different tissues and organs to produce a distinctive pattern of echoes. A receiver "hears" the returning echo pattern and forwards it to a special computer, which translates the data into an image on a television screen. Ultrasound is better than x rays at distinguishing subtle variations between soft, fluid-filled tissues, so it is particularly useful in providing diagnostic images of the abdomen, breast, eye, pelvis, scrotum, and thyroid. Unlike x rays, it does not damage tissues with ionizing radiation. Improvements in the technology, application, and interpretation of ultrasound continue. Its low cost, portability, versatility, safety, andspeed have made it a popular medical imaging technique. Ultrasound remains faster and less expensive than computed tomography scans (CT), its primary rival.
Ultrasound technology can also be used for treatment purposes. The direct therapeutic value of ultrasonic waves lies in their mechanical nature. They areshock waves, just like audible sound, and vibrate the materials through whichthey pass. These vibrations are mild and virtually unnoticeable at the frequencies and intensities used for imaging. However, strongly focused, high-intensity, high-frequency ultrasound can also be used to destroy certain types oftumors, as well as gallstones. High-intensity ultrasound is useful for treating soft tissue injuries, such as strains, tears and associated scarring; theheating and agitation they cause are believed to promote rapid healing through increased circulation. Ultrasound is most frequently used therapeuticallyas a visual aid during surgical procedures--such as guiding needle placementto drain fluid from a cyst, or to extract tumor cells for analysis.
Ultrasound is valuable for finding the reason for abdominal pain, which can signal anything from organ malfunction or injury to malignant growths. In thecase of abdominal trauma, such as after a car crash or a fall, ultrasound canpinpoint the location, cause, and severity of hemorrhaging or locate a foreign object, such as a bullet.
In breast ultrasound, the sound waves pass through the breast and bounce backor echo from various tissues to form a picture of the internal structures. Its most common application is to investigate a specific area of the breast where a problem is suspected. A palpable lump and/or an abnormality discoveredon an x ray (mammogram) can be further evaluated by ultrasound. It is especially helpful in distinguishing between a fluid-filled cyst and a solid mass such as a tumor.
Breast ultrasound is often the first step taken to evaluate masses in women under 35 whose mammograms can be difficult to interpret because of their denser breast tissue. The lack of radiation used with ultrasound also makes it ideal for studying breast abnormalities in women who are pregnant, and it is effective in assessing breast implants for leakage or rupture. Breast inflammation, where pockets of infection or abscesses may form, can be diagnosed and monitored by ultrasound.
Ultrasound imaging equipment also allows eye specialists (ophthalmologists) to "see" the eye in great detail without the pain and risk of exploratory surgery or the limitations and uncertainty inherent in traditional visual examination. Ultrasound is used to detect and diagnose many eye diseases and injuries, to measure the eye prior to corrective surgery, and to treat problems. When presented with general symptoms, ultrasound can speed diagnosis if a serious condition is suspected. A special type of ultrasound, known as Doppler, caneven perceive and measure circulation in the tiny blood vessels of the eye.
Ultrasound can reveal the exact type, extent, and location of damage in the eye, from deformations and ruptures to internal bleeding, and so can assist emergency care efforts. Ophthalmic ultrasound imaging is also used routinely toguide the precise placement of instruments during surgery, and can be used directly for the treatment of glaucoma and tumors of the eye.
Pelvic ultrasound is most commonly performed during pregnancy. Early in the pregnancy, it might be used to determine the size of the uterus or the fetus,to detect multiple or ectopic pregnancy, to confirm that the fetus is alive,or to confirm the due date. Toward the middle of the pregnancy, ultrasound can confirm fetal growth, reveal anatomical defects, and check the placenta. Toward the end of pregnancy, it can evaluate fetal size, position, and growth.Doctors may also use ultrasound to guide them during diagnostic procedures like amniocentesis and chorionic villus sampling. Both of these tests use longneedles inserted through the mother's abdomen into the uterus or placenta togather cells.
Scrotal ultrasound is an imaging technique used to diagnose suspected abnormalities of the scrotum. It is the primary imaging method used to evaluate disorders of the testicles and surrounding tissues, such as an absent or undescended testicle, an inflammation problem, a fluid collection, abnormal blood vessels, or a mass.
Thyroid ultrasound is an imaging technique used for diagnosing suspected thyroid disease, such as a goiter. The thyroid gland is an organ located in frontof the neck that plays an important role in controlling the body's metabolism. Specialized thyroid ultrasounds, such as color Doppler flow studies, can add valuable information. By showing an image of the blood circulation in thegland, this study can assess some ambiguous masses in greater detail to further refine diagnosis.
Ultrasound studies may also be done periodically to assess the response of the thyroid gland to medical therapy. Patients who have received therapeutic radiation to the head or neck are also monitored at regular intervals using thyroid ultrasound, since they have a higher risk of thyroid cancer and other abnormalities.