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Ultrasound is sound with frequencies greater than 20 kilohertz. [1] This frequency is the approximate upper audible limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, including ultrasound. Ultrasonic devices operate with frequencies from 20 kHz up to several gigahertz.
Ultrasound probe (curvilinear type) is used for examination of superficial structures. Abdominal ultrasonography (also called abdominal ultrasound imaging or abdominal sonography ) is a form of medical ultrasonography ( medical application of ultrasound technology) to visualise abdominal anatomical structures.
Strong, short electrical pulses from the ultrasound machine drive the transducer at the desired frequency. The frequencies can vary between 1 and 18 MHz, though frequencies up to 50–100 megahertz have been used experimentally in a technique known as biomicroscopy in special regions, such as the anterior chamber of the eye.
All modern ultrasound scanners use pulsed Doppler to measure velocity. Pulsed wave instruments transmit and receive series of pulses. The frequency shift of each pulse is ignored, however the relative phase changes of the pulses are used to obtain the frequency shift (since frequency is the rate of change of phase).
The PA probe consists of many small ultrasonic transducers, each of which can be pulsed independently.By varying the timing, for instance by making the pulse from each transducer progressively delayed going up the line, a pattern of constructive interference is set up that results in radiating a quasi-plane ultrasonic beam at a set angle depending on the progressive time delay.
The transducer may be used in contact with the skin, as in fetal ultrasound imaging, or inserted into a body opening such as the rectum or vagina. Clinicians who perform ultrasound-guided procedures often use a probe positioning system to hold the ultrasonic transducer. [9] Compared to other medical imaging modalities, ultrasound has several ...
Ultrasound involves a probe that is placed near a structure and uses the transmission of ultrasound waves through a structure to produce images, after computer processing. [1] Ultrasound of the urinary tract is performed by a probe placed on the abdominal wall, called a transducer. [1] This occurs while a person is lying down. [1]
Transvaginal ultrasonography – Ultrasound is performed through the vagina; Transabdominal ultrasonography – Ultrasound is performed across the abdominal wall or through the abdominal cavity; In normal state, each body tissue type, such as liver, spleen or kidney, has a unique echogenicity. Fortunately, gestational sac, yolk sac and embryo ...