An echocardiogram uses 4.4 MHz ultrasound to measure blood flow in the aorta. Th

Question

An echocardiogram uses 4.4 MHz ultrasound to measure blood flow in the aorta. The blood is moving away from the probe at 1.3m/s .

Part A

What is the frequency shift of the reflected ultrasound? Use values given in (Figure 1) if necessary. Enter a positive value if the received frequency is higher than the emitted frequency, and a negative value if the received frequency is lower than the emitted frequency.

The speed of sound Medium Air (0C) Air (20°C) Helium (0°C) Ethyl alcohol Water Human tissue (ultrasound Lead Aluminum Granite Diamond Speed (m/s) 331 343 970 1170 1480 1540 1200 5100 6000 12.000

Explanation / Answer

When blood is moving away from probe then,

      fultrasound=fapllied to aorta [(v-v0)/(v+vs)]

                   = 4.4Mz * (1540 - 1.6) / (1540 + 1.6)

                  = 4.391 MHz

?f = f' - f = (4.391 - 4.4)MHz = -9133 Hz

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