The descriptor for a Doppler shift where the received frequency exceeds the transmitted frequency is:

The descriptor for a Doppler shift where the received frequency exceeds the transmitted frequency is:

• A. Negative
• B. Positive
• C. Zero
• D. Double

Answer: (B)

In Doppler ultrasound, the sign of the frequency shift tells you the direction of motion relative to the transducer. If the received frequency is higher than the transmitted frequency, the Doppler shift is positive. That positive shift indicates flow toward the probe along the beam, since the moving target compresses the wavefronts and raises the frequency it returns. When the motion is away from the transducer, the shift is negative; no motion along the beam yields zero. A descriptor of "positive" fits the situation where fR exceeds fT.

In Doppler ultrasound, the sign of the frequency shift tells you the direction of motion relative to the transducer. If the received frequency is higher than the transmitted frequency, the Doppler shift is positive. That positive shift indicates flow toward the probe along the beam, since the moving target compresses the wavefronts and raises the frequency it returns. When the motion is away from the transducer, the shift is negative; no motion along the beam yields zero. A descriptor of "positive" fits the situation where fR exceeds fT.