Which of the following is NOT a variable affecting the Doppler shift?

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Multiple Choice

Which of the following is NOT a variable affecting the Doppler shift?

Doppler shift in ultrasound is determined by the transmitted frequency, the velocity of blood along the beam, the angle between flow and the beam, and the speed of sound in tissue. The basic relationship is f_D = 2 f0 v cos θ / c. This means the shift grows with higher transmitted frequency, greater velocity component toward or away from the transducer (as long as cos θ is not zero), and with a smaller speed of sound in tissue. The angle between flow and beam is crucial because cos θ modulates how much of the actual blood velocity contributes to the shift. Heart rate does not appear in this equation. It sets how often certain velocity patterns occur over time (pulse timing and waveform systole/diastole), but it does not change the instantaneous Doppler frequency shift itself. So heart rate is not a variable that directly affects the Doppler shift.

Doppler shift in ultrasound is determined by the transmitted frequency, the velocity of blood along the beam, the angle between flow and the beam, and the speed of sound in tissue. The basic relationship is f_D = 2 f0 v cos θ / c. This means the shift grows with higher transmitted frequency, greater velocity component toward or away from the transducer (as long as cos θ is not zero), and with a smaller speed of sound in tissue. The angle between flow and beam is crucial because cos θ modulates how much of the actual blood velocity contributes to the shift.

Heart rate does not appear in this equation. It sets how often certain velocity patterns occur over time (pulse timing and waveform systole/diastole), but it does not change the instantaneous Doppler frequency shift itself. So heart rate is not a variable that directly affects the Doppler shift.

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