d) Doppler scan

• doppler scan

• the transducer is placed over the blood vessel at an angle

• the transducer sends ultrasound pulses through the body

  • reflected off tissues → received with the same frequency

  • reflected off blood moving away from the transducer → received with decreased frequency

  • reflected off blood moving towards the transducer → received with increased frequency

• computer displays a colour-coded image depending on the direction of blood

• the doppler scan equation

• Δf = (2fvcosθ)/c

  • change in ultrasound frequency (Hz) = (2 × initial ultrasound frequency (Hz) x speed of blood (ms-1) × cosine(angle between the pulse and the skin)) / speed of ultrasound in blood (ms^-1)

  
  

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