Question

For a pulse repetition frequency (PRF) of 10,000 Hz and ultrasound frequency of 2 MHz, what's the maxiμm velocity, in m/s, that can be measured without aliasing using PW Doppler? Assume the speed of sound to be 1,540 m/s.

a) 77 m/s
b) 154 m/s
c) 385 m/s
d) 308 m/s

Answer 1

The maximum velocity that can be measured without aliasing using PW Doppler with a PRF of 10,000 Hz and an ultrasound frequency of 2 MHz is 77 m/s, which corresponds to the Nyquist limit of half the PRF value.

Step-by-step explanation:

To calculate the maximum velocity that can be measured without aliasing using PW Doppler with a pulse repetition frequency (PRF) of 10,000 Hz and an ultrasound frequency of 2 MHz, the Nyquist limit must be used. The Nyquist limit is half the PRF, which in this case is 5,000 Hz. The equation to calculate the maximum Doppler shift that can be detected without aliasing is fD = (v * 2f0) / c, where fD is the Doppler frequency shift, v is the blood velocity, f0 is the transmitted ultrasound frequency, and c is the speed of sound in the medium. Rearranging this equation to solve for v, we get v = (c * fD) / (2f0). Plugging the numbers into this equation: v = (1540 m/s * 5000 Hz) / (2 * 2,000,000 Hz) results in a calculated velocity of 77 m/s, which is option (a).