Ultrasonography

ultrasonography /ul·tra·so·nog·ra·phy/ (-so-nog´rah-fe) the imaging of deep structures of the body by recording the echoes of pulses of ultrasonic waves directed into the tissues and reflected by tissue planes where there is a change in density. Diagnostic ultrasonography uses 1–10 megahertz waves.ultrasonograph´ic

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Doppler ultrasonography  that in which the shifts in frequency between emitted ultrasonic waves and their echoes are used to measure the velocities of moving objects, based on the principle of the Doppler effect. The waves may be continuous or pulsed; the technique is frequently used to examine cardiovascular blood flow (Doppler echocardiography).

gray-scale ultrasonography  a B-scan technique in which the strength of echoes is indicated by a proportional brightness of the displayed dots.

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ul·tra·so·nog·ra·phy (ltr-s-ngr-f)

n.

Diagnostic imaging in which ultrasound is used to visualize an internal body structure or a developing fetus. Also called echography, sonography.

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ultra·so·nogra·pher n.

ultra·sono·graphic (-sn-grfk, -sn-) adj.

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Ultrasonography

A process that uses the reflection of high-frequency sound waves to make an image of structures deep within the body. Ultrasonography is routinely used to detect fetal abnormalities.

Mentioned in: Ascites, Cholestasis, Eye Examination, Mental Retardation, Pelvic Ultrasound, Pyloric Stenosis, Splenic Trauma, Transient Ischemic Attack

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ultrasonography,

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.

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ultrasonography

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.

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A-mode ultrasonography

(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 ultrasonography

(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 ultrasonography

see doppler ultrasound.

endoscopic ultrasonography

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 ultrasonography

B-mode ultrasonography in which the strength of echoes is indicated by a proportional brightness of the displayed dots.

M-mode ultrasonography

(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 ultrasonography

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.