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Ultrasound energy, simply known as ultrasound, is a type of mechanical energy called sound characterized by vibrating or moving particles within a medium. Ultrasound is distinguished by vibrations with a frequency greater than 20,000 Hz, compared to audible sounds that humans typically hear with frequencies between 20 and 20,000 Hz.
Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz". In air at atmospheric pressure, ultrasonic waves have wavelengths of 1.9 cm or less. Ultrasound can be generated at very high frequencies; ultrasound is used for sonochemistry at frequencies up to multiple hundreds of kilohertz.
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 ...
Sound from ultrasound is the name given here to the generation of audible sound from modulated ultrasound without using an active receiver. This happens when the modulated ultrasound passes through a nonlinear medium which acts, intentionally or unintentionally, as a demodulator .
A JVP waveform. The jugular venous pulsation has a biphasic waveform. The a wave corresponds to right atrial contraction and ends synchronously with the carotid artery pulse. The peak of the 'a' wave demarcates the end of atrial systole. The x descent follows the 'a' wave and corresponds to atrial relaxation and rapid atrial filling due to low ...
However, in non-contact ultrasound, ambient air is the only acoustic coupling medium. An electromagnetic acoustic transducer (EMAT), is a type of non-contact ultrasound that generates an ultrasonic pulse which reflects off the sample and induces an electric current in the receiver. This is interpreted by software and provides clues about the ...
Medical ultrasound includes diagnostic techniques (mainly imaging techniques) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, muscles, joints, blood vessels, and internal organs, to measure some characteristics (e.g., distances and velocities) or to generate an informative audible sound.
The ultrasound probe emits a high-frequency sound wave (usually a multiple of 2 MHz) that bounces off various substances in the body. These echoes are detected by a sensor in the probe. In the case of blood in an artery , the echoes have different frequencies depending on the direction and speed of the blood because of the Doppler effect . [ 2 ]