4/25/2023 0 Comments Bowel gas artifact meaning![]() If the two mediums have different “stiffness” the resulting change in propagation speeds will cause the wave to be “bent” from its original path ( refraction).The remaining sound wave travels through the second medium (or tissue).The angle of approach (incidence) is identical to the angle of the reflection. ![]() Some of the waves bounce back towards the source as an echo ( reflection).These occur as sound waves encounter a boundary between two different media.Hearing range in various animals and humans. Other causes of attenuation are reflection, refraction and scatter.The major source of attenuation in soft tissue is absorption, the conversion of acoustic energy into heat.Attenuation is the loss of intensity and amplitude as sound waves travel through a medium.Sound waves travel through human soft tissue at approximately 1540 m/s (about one mile per second).This means that sound waves travel faster in solids than liquids or gases The greater the stiffness, the faster the wave will travel.The propagation speed of an acoustic wave traveling through a specific medium is determined by the stiffness of that medium.Diagnostic ultrasound typically uses frequencies between 2 and 20 million Hertz (Megahertz - MHz).Ultrasound refers to any sound waves with frequencies greater than 20kHz.For most humans audible sound ranges between 20 Hz and 20,000 Hz (20 kHz).The illustration shows a schematic drawing of wave length, pressure and amplitude. The frequency of the wave is measured in cycles per second or Hertz (cycles/s, Hz) (Illustration 1).The wavelength is the distance traveled during one cycle.One cycle of the acoustic wave is composed of a complete positive and negative pressure change.Sound is a series of pressure waves propagating through a medium.This includes standard machine functionality and transducer manipulation. This chapter serves as a basic overview of ultrasound physics and image acquisition.
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