Medical Imaging Systems · Ultrasound Imaging · 1 mark · Numerical answer
A 5 MHz ultrasound transducer measures blood velocity using an echo frequency shift of 200 Hz. The beam makes 45° with blood flow, and sound speed is 1500 m/s. Find blood velocity in cm/s to one decimal place.
The round-trip Doppler relation is Δf=2f₀v cosθ/c. Hence v=200×1500/[2×5×10⁶×cos45°]=0.042426 m/s. Converting metres to centimetres gives 4.2426 cm/s, which rounds to 4.2. The factor two comes from transmission toward and reflection from the moving scatterer.
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