ultrasonography

(ŭl'trə-sə-nŏg'rə-fē)
n.

1. Diagnostic imaging in which ultrasound is used to image an internal body structure or a developing fetus.
2. An imaging technique that uses high frequency sound waves to visualize underwater surfaces, boundaries, objects, and currents. In both senses also called echography.

ultrasonographer ul'tra·so·nog'ra·pher n.
ultrasonographic ul'tra·son'o·graph'ic (-sŏn'ə-grăf'ĭk, -sō'nə-) adj.

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Key Terms: Biopsy, Endoscopy.

Definition

Ultrasonography is the study of internal organs or blood vessels using high-frequency sound waves. The actual test is called an ultrasound scan or sonogram. Duplex ultrasonography uses Doppler technology to study blood cells moving through major veins and arteries. There are several types of ultrasound. Each is used in diagnosing specific parts of the body.

Purpose

An ultrasound is a noninvasive, safe method of examining a patient's eyes, pelvic or abdominal organs, breast, heart, or arteries and veins. It is often used to diagnosis disease, locate the source of pain, or look for stones in the kidney or gallbladder. Ultrasound produces images in real time. Images appear on the screen instantly. It may also be used to guide doctors who are performing a needle biopsy to locate a mass. (Needle biopsies are often used to obtain a sample of breast tissue to test for cancer cells.) Duplex/Doppler ultrasound aids in diagnosing a blockage in or a malformation of the vessel. Different color flows aid in identifying problem areas in smaller vessels. Endoscopic ultrasound combines a visual endoscopic exam, during which a flexible tube called an endoscope is threaded down the throat, with an ultrasound test. The ultrasound probe is attached to the end of the endoscope. An endoscopic ultrasound is helpful in determining how deeply a tumor has grown into normal tissues or the gastrointestinal tract. During a transvaginal ultrasound, the ultrasound probe is inserted into the vagina to obtain better images of the ovaries and uterus. Color flow Doppler imaging, using a transvaginal probe, is being performed to detect abnormal blood flow patterns associated with ovarian cancer.

Precautions

Ultrasound is considered safe with no known risks or precautions. The exam uses no radiation. Under normal circumstances the exam is normally painless. However, if the patient has a full bladder, pressure exerted during the exam may feel uncomfortable. An ultrasound conducted in conjunction with an invasive exam carries the same risks as the invasive exam.

Description

The patient will be asked to lie still on an exam table in a darkened room. The darkness helps the technician see images on a screen, which is similar to a computer monitor. Sometimes the patients are positioned so they can watch the screen. The technician will apply a lubricating gel to the skin over the area to be studied. Ultrasound uses high-frequency sound waves to produce an image. A small wand-like device called a transducer produces sound waves that are sent into the body when the device is pressed against the skin. The gel helps transmit the sound waves, which do not travel through the air. Neither the patient nor the technician can hear the sound waves. The technician moves the device across the skin in the area to be studied. The sound waves bounce off the fluids and tissues inside the body. The transducer picks up the return echo and records any changes in the pitch or direction of the sound. The image is immediately visible on the screen. The technician may print a still picture of any significant images for later review by the radiologist.

Preparation

Depending on the type of ultrasound ordered, patients may not need to do anything prior to the test. Other ultrasound studies may require that the patient not eat or drink anything for up to 12 hours prior to the exam, in order to decrease the amount of gas in the bowel. Intestinal gas may interfere in obtaining accurate results. The patient must have a full bladder for some exams and an empty bladder for others.

Aftercare

Remove any gel still left on the skin. No other aftercare is required following an ultrasound.

Risks

Standard, diagnostic ultrasound is considered risk-free. Risks may be associated with invasive tests conducted at the same time, such as an endoscopic ultrasound or an ultrasound-guided needle biopsy.

Normal Results

An ultrasound scan is considered normal when the image depicts normally shaped organs or normal blood flow.

Questions to Ask the Doctor

• Did you see any abnormalities?
• What future care will I need?

Abnormal Results

Abnormal echo patterns may represent a condition requiring treatment. Any masses, tumors, enlarged organs or blockages in the blood vessel are considered abnormal. Additional testing may be ordered.

Resources

Books

Pfenninger, John L. Procedures for Primary Care Physicians. 2nd ed. St. Louis: Mosby-Year Book, Inc. 2000.

Rosen, Peter. Emergency Medicine: Concepts and Clinical Practice. St. Louis: Mosby-Year Book, Inc. 1999.

—Debra Wood, R.N.

The use of sound frequencies above 30 kHz to produce images of structures within the human body. A beam of ultrasound is directed into the body and its echoes are electrically analysed to produce the image.

An imaging technique in which deep structures of the body are visualized by recording the reflections (echoes) of ultrasonic waves directed into the tissues.
Frequencies in the range of 1 million to 10 million hertz are used in diagnostic ultrasonography. The lower frequencies provide a greater depth of penetration and are used to examine abdominal organs; those in the upper range provide less penetration and are used predominantly to examine more superficial structures such as the eye.
The basic principle of ultrasonography is the same as that of depth-sounding in oceanographic studies of the ocean floor. The ultrasonic waves are confined to a narrow beam that may be transmitted through, refracted, absorbed, or reflected by the medium toward which they are directed, depending on the nature of the surface they strike.
In diagnostic ultrasonography the ultrasonic waves are produced by electrically stimulating a piezoelectric crystal called a transducer. As the beam strikes an interface or boundary between tissues of varying acoustic impedance (e.g. muscle and blood) some of the sound waves are reflected back to the transducer as echoes. The echoes are then converted into electrical impulses that are displayed on an oscilloscope, presenting a ‘picture’ of the tissues under examination.
Ultrasonography can be utilized in examination of the heart (echocardiography) and in identifying size and structural changes in organs in the abdominopelvic cavity. It is, therefore, of value in identifying and distinguishing cancers and benign cysts. The technique also may be used to evaluate tumors and foreign bodies of the eye, and to demonstrate retinal detachment. Ultrasonography is not, however, of much value in examination of the lungs because ultrasound waves do not pass through structures that contain air.
A particularly important use of ultrasonography is in the field of obstetrics and gynecology. It is a fast, relatively safe, and reliable technique for diagnosing pregnancy, and for detecting some typical fetal anomalies.

• A-mode u. — (amplitude modulation) that in which on the cathode-ray tube (CRT) display one axis represents the time required for the return of the echo and the other corresponds to the strength of the echo, as in echoencephalography.
• B-mode u. — (brightness modulation) that in which the position of a spot on the CRT display corresponds to the time elapsed (and thus to the position of the echogenic surface) and the brightness of the spot to the strength of the echo; movement of the transducer produces a sweep of the ultrasound beam and a tomographic scan of a cross-section of the body.
• Doppler u. — see doppler ultrasound.
• endoscopic u. — a high resolution ultrasound transducer, mounted on a flexible endoscope, can be used to gain images from within a hollow organ, such as the gastrointestinal tract. This overcomes some of the problems ingesta and fecal material cause in other methods of ultrasound examination.
• gray-scale u. — B-mode ultrasonography in which the strength of echoes is indicated by a proportional brightness of the displayed dots.
• M-mode u. — (motion mode) a type of B-mode ultrasonography in which spots on the CRT display produce a tracing of the motion of echogenic objects. Used in echocardiography.
• real-time u. — B-mode ultrasonography using an array of detectors so that scans can be made electronically at a rate of 30 frames a second, thus giving a true display of motion, such as that of the heart.

n

The process of imaging deep structures of the body by measuring and recording the reflection of pulsed or continuous high-frequency sound waves. It is valuable in many medical situations, including the diagnosis of fetal abnormalities, gallstones, heart defects, and tumors. Also called sonography.

For a list of words related to echography, see:

• Procedures - echography: use of ultrasound waves to display and analyze body’s internal structure

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