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Medical imaging

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Question 22

An ultrasound scan is a non-invasive medical imaging technique widely used in both human and veterinary medicine to visualize internal structures and measure dynamic physiological processes.

a.

Explain what is meant by ultrasound waves.

[2]
b.

Explain how a single piezoelectric transducer is used to both generate and detect ultrasound pulses during a medical scan, and explain why an acoustic coupling gel must be applied to the patient's skin.

[4]
c.

During a fetal ultrasound scan:

Explain why virtually no ultrasound signal is reflected back from within a large volume of uniform amniotic fluid.

[1]
d.

During a fetal ultrasound scan:

Explain why the boundary between fetal skull bone and brain tissue produces a much stronger reflection signal than the boundary between two different types of soft tissues within the brain.

[2]
e.

A veterinary Doppler ultrasound system is used to assess the speed of blood flow in a horse's carotid artery.

  • The speed of ultrasound in horse blood is 1540 m s−11540 \text{ m s}^{-1}1540 m s−1.
  • A transducer emitting ultrasound at a frequency of 9.0000 MHz9.0000 \text{ MHz}9.0000 MHz is directed at an angle of 38∘38^\circ38∘ to the direction of the blood flow.
  • The frequency of the reflected ultrasound received back by the transducer is 8.9974 MHz8.9974 \text{ MHz}8.9974 MHz.

Calculate the speed vvv of the blood flow. Give your answer to 2 significant figures.

[3]

Medical imaging Questions

  1. A Level
  2. /Physics
  3. /Medical imaging