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(sonography) n. the use of ultrasound to produce images of structures in the human body. The ultrasound probe sends out a short pulse of high-frequency sound and detects the reflected waves (echoes) occurring at interfaces within the organs. The direction of the pulse can then be moved across the area of interest with each pulse to build up a complete image. Scans may produce a single stationary image similar to a photograph (static) or multiple sequential images similar to a video (real-time imaging). The ultrasound waves are transmitted from – and echoes detected by – piezoelectric crystals contained within the scanning probe (see transducer). As far as is known, there are no adverse effects from the use of ultrasound at diagnostic energies. Ultrasound waves are blocked by gas, as in the lungs and bowel, which can obscure underlying structures. The detail seen increases with the frequency of the ultrasound but the depth of penetration decreases. Ultrasonography is extensively used in obstetrics, including the diagnosis of pregnancy, assessment of gestational age, diagnosis of malpresentations, ectopic pregnancies, and hydatidiform moles, and detection of structural fetal abnormalities (See also transvaginal ultrasonography). It is also used to examine the abdominal organs, urinary tract, blood vessels, muscles, and tendons. More specialized techniques include echocardiography, transrectal ultrasonography (TRUS), intraoperative ultrasound (IOUS), and endoscopic ultrasound examinations. see also Doppler ultrasound.

Subjects: Physics — Medicine and Health.

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