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In The Name Of God

In The Name Of God. CHAPTER 2. Attenuation in tissues. Absorption coefficient Attenuation coefficient Neper Scattering coefficient. Key terms. ATTENUATION.

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In The Name Of God

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  1. In The Name Of God CHAPTER 2 Attenuation in tissues

  2. Absorption coefficient Attenuation coefficient Neper Scattering coefficient Key terms

  3. ATTENUATION Attenuation includes the effects of both scattering and absorption in the loss of pressure amplitude as the ultrasound wave propagates through a medium.

  4. Amplitude attenuation coefficient (α) The amplitude attenuation coefficient (α) is given by sum of the scattering coefficient (αs ) and absorption coefficient (αa) α= αa +αs and we have: Maximum particle velocity (u0) and maximum displacement (s0) are related according to: u0=p0/ρc and s0=p0/(2пfcρ)

  5. ABSORPTION Amplitude Absorption coefficient of the ultrasonic beam follows an exponential function. P0 and Pm are pressure and peak pressure at a point

  6. Intensity Intensity describes the amount of energy flowing through a unit cross sectional area per unit of time. The intensity of the beam also decreases exponentially with distance from the sound source:

  7. Neper The special unit for these coefficient is the Neper (NP) per centimeter. The attenuation coefficient at 1 MHZ for various tissue types are different.

  8. Amplitude equation for decibels Level (db)= 10 log Level (db)= 20 log dB=8.868np

  9. decibeles and HVL

  10. Calculation of attenuation loss The intensity loss in decibles caused by attenuation as the ultrasound beam passes through a medium is: Intensity loss (dB) = μfz

  11. Attenuation and reflection losses Attenuation refers to all processes (except reflection) that act to reduce ultrasound intensity.

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