Answer #52

The correct answer is B, 7 KHz. To answer this question you need to simply know the equation for the Nyquist limit.

The Doppler frequency above which there is aliasing is called the Nyquist limit. We are used to thinking about this in term of velocited on the ultrasound machine, but in reality the limit is a frequency shift, which is then translated by the machine into a velocity. The Nyquist limit is equal to half the pulse repetition frequency (PRF) which is how often the machine sends out a pulse. We are given a PRF of 14 KHz, hence 14/2 is 7 KHz