Published on 06/02/2015 by admin
Filed under Anesthesiology
Last modified 06/02/2015
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3 Attenuation
Attenuation is a decrease in wave amplitude as it travels through a medium. The attenuation of ultrasound in soft tissue is about 0.8 dB/(MHz-cm), indicating that the extent of attenuation depends on the distance traveled and the frequency of insonation. The units of the attenuation coefficient directly show the greater attenuation of high-frequency ultrasound beams. In soft tissue, 80% or more of the total attenuation is caused by absorption of the ultrasound wave, thereby generating heat.
Time gain compensation (TGC) adjusts for attenuation of an ultrasound beam as a function of depth. When TGC is properly adjusted, images of similar reflectors appear the same regardless of depth.
Atlas of Ultrasound-Guided Regional Anesthesia 2e
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