transducer (frequency r) Doppler frequency (fd-2. ft. V. cost beam fd- doppler s

Question

transducer (frequency r) Doppler frequency (fd-2. ft. V. cost beam fd- doppler shift c is speed of sound in tissue ft - transmited beam V - velocity of the blood 0- angle of incidence between the ultrasound beam and the direction of the flow Higher Doppler frequency obtained if: velocity is increased - beam is more aligned to flow direction - higher frequency is used flow velocity = V 6. Using the Doppler frequency equation, shown in the figure above: 1) 45°, find the If a 10 MHz ultrasound is used, for blood flow of 15cm/second and Doppler frequency. 2) Ifa 10 MHz ultrasound is used, 1 kHz Doppler shift is found, calculate blood flow velocities for 40% 10.50° (an excel table may save your time) 3) Ifa 10 MHz ultrasound is used, 1 kHz Doppler shift is found, the inner diameter (ID) of the artery is 3mm, calculate blood volume passing through the measurement point in 1 second, assuming a constant flow,

Explanation / Answer

The doppler frequency is given by:

fd = 2 f v cos(theta)/c

value of c is not given, but in general

c = 1540 m/s

1)fd = 2 x 10 x 10^6 x 0.15 x cos45/1540 = 1377.48 Hz

Hence, fd = 1377.48 Hz = 1.38 x 10^3 Hz = 1.38 kHz

2)Using the same eqn and solving for v we get

v = fd c/2 f cos(theta)

v1 = 1000 x 1540/2 x 10 x 10^6 x cos40 = 0.101 m/s

v1 = 10.1 cm/s = 0.101 m/s

v2 = 1000 x 1540/2 x 10 x 10^6 x cos1 = 0.143 m/s

v2 = 14.3 cm/s = 0.143 m/s

v3 = 1000 x 1540/2 x 10 x 10^6 x cos40 = 0.1198 m/s = 0.12

v3 = 12 cm/s = 0.12 m/s

3)what is angle now?

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