Ultrasonography

Ultrasound

What is an ultrasound?

An ultrasound procedure is a noninvasive (the skin is not pierced) diagnostic procedure used to assess soft tissue structures such as muscles, blood vessels, and organs.

Ultrasound uses a transducer that sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer is placed at certain locations and angles, the ultrasonic sound waves move through the skin and other body tissues to the organs and structures within. The sound waves bounce off the organs like an echo and return to the transducer. The transducer picks up the reflected waves, which are then converted by a computer into an electronic picture of the organs or tissues under study.

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Different types of body tissues affect the speed at which sound waves travel. Sound travels the fastest through bone tissue, and moves most slowly through air. The speed at which the sound waves are returned to the transducer, as well as how much of the sound wave returns, is translated by the transducer as different types of tissue.

A clear conducting gel is placed between the transducer and the skin to allow for smooth movement of the transducer over the skin and to eliminate air between the skin and the transducer for the best sound conduction.

By using an additional mode of ultrasound technology during an ultrasound procedure, blood flow can be assessed. An ultrasound transducer capable of assessing blood flow contains a Doppler probe. The Doppler probe within the transducer evaluates the velocity and direction of blood flow in the vessel by making the sound waves audible. The degree of loudness of the audible sound waves indicates the rate of blood flow within a blood vessel. Absence or faintness of these sounds may indicate an obstruction (blockage) of blood flow.

Ultrasounds are used to view internal organs as they function (in "real time," like a live TV broadcast), and to assess blood flow through various vessels. Ultrasound procedures are often used to examine many parts of the body such as the abdomen, breasts, female pelvis, prostate, scrotum, thyroid and parathyroid glands, and the vascular system. During pregnancy, ultrasounds are performed to evaluate the development of the fetus.

Technological advancements in the field of ultrasound now include images that can be made in a three-dimensional view (3-D) and/or four dimensional (4-D) view. The added dimension of the 4-D is motion, so that it is a 3-D view with movement.

What are the different types of ultrasound procedures?

Different ultrasound techniques exist for different conditions. Examples of some of the more common types of ultrasound examinations include the following:

• Doppler ultrasound. Used to see structures inside the body, while evaluating blood flow at the same time. Doppler ultrasound can determine if there are any problems within the veins and arteries.

• Vascular ultrasound. Used to see the vascular system and its function, including detection of blood clots.

• Echocardiogram. Used to see the heart and its valves, and to evaluate the effectiveness of the heart's pumping ability.

• Abdominal ultrasound. Used to detect any abnormalities of the abdominal organs (i.e., kidneys, liver, pancreas, gallbladder), such as gallstones or tumors.

• Renal ultrasound. Used to examine the kidneys and urinary tract.

• Obstetrical ultrasound. Used to monitor the development of the fetus.

• Pelvic ultrasound. Used to find the cause of pelvic pain, such as an ectopic pregnancy in women, or to detect tumors or masses.

• Breast ultrasound. Used to examine a mass in the breast tissue.

• Thyroid ultrasound. Used to see the thyroid and to detect any abnormalities.

• Scrotal ultrasound. Used to further investigate pain in the testicles.

• Prostate ultrasound. Used to examine any nodules felt during a physical examination.

• Musculoskeletal ultrasound. Used to examine any joint or muscle pain for conditions, such as a tear.

• Interventional ultrasound. Used to help the surgeon during a minimally invasive operation or biopsy.

• Intravascular ultrasound (IVUS). Used to provide direct visualization and measurement of the inside of blood vessels.

• Endoscopic ultrasound. Used to obtain direct ultrasound examination of the inside of a body cavity or organ, using an ultrasound transducer inside an endoscope (a small, flexible tube with a light and a lens on the end).

How are ultrasounds performed?

An ultrasound procedure may be done on an outpatient basis, or as part of inpatient care. Although each facility may have specific protocols in place, generally, an ultrasound procedure follows this process:

1. A gel-like substance will be smeared on the area of the body to undergo the ultrasound (the gel acts as a conductor).

2. Using a transducer, a tool that sends ultrasound waves, the ultrasound will be sent through the patient's body.

3. The sound from the transducer will be reflected off structures inside the body, and the information from the sounds will be analyzed by a computer.

4. The computer will create an image of these structures on a television screen. The moving pictures can be recorded on film videotape.

5. There are no confirmed adverse biological effects on patients or instrument operators caused by exposures to ultrasound.