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Non-ionising imaging (A-level only)

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Question 5

An ultrasound scan of frequency 2.5 MHz2.5\text{ MHz}2.5 MHz is used to image a boundary between muscle and bone.

1.

Estimate the resolution of the scan in muscle, assuming the resolution is approximately equal to the wavelength of the ultrasound in the tissue.

[2]
2.

Calculate the acoustic impedances of muscle and bone using the data below.

[3]
3.

Calculate the percentage of the incident ultrasound intensity that is transmitted across the muscle-bone boundary.

Data:

  • Speed of sound in muscle = 1590 m s−11590\text{ m s}^{-1}1590 m s−1
  • Density of muscle = 1040 kg m−31040\text{ kg m}^{-3}1040 kg m−3
  • Speed of sound in bone = 4080 m s−14080\text{ m s}^{-1}4080 m s−1
  • Density of bone = 1900 kg m−31900\text{ kg m}^{-3}1900 kg m−3
[3]

Non-ionising imaging (A-level only) Questions

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  3. /Non-ionising imaging (A-level only)