The relationship between received and transmitted frequencies defines which Doppler sign category?

The relationship between received and transmitted frequencies defines which Doppler sign category?

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

Answer: (A)

Doppler sign is determined by the difference between what the transducer sends and what it receives from moving blood. If the reflected frequency is higher than the transmitted frequency, the Doppler shift is positive, indicating flow toward the transducer. If the reflected frequency is lower, the shift is negative, indicating flow away from the transducer; if they’re equal, the shift is zero. This positive relationship happens because moving targets toward the probe compress the wave fronts, increasing frequency, while movement away stretches them and lowers the frequency. In clinical Doppler, the sign of the shift tells you the direction of flow relative to the probe, so a higher received frequency compared to transmitted corresponds to a positive Doppler sign.

Doppler sign is determined by the difference between what the transducer sends and what it receives from moving blood. If the reflected frequency is higher than the transmitted frequency, the Doppler shift is positive, indicating flow toward the transducer. If the reflected frequency is lower, the shift is negative, indicating flow away from the transducer; if they’re equal, the shift is zero. This positive relationship happens because moving targets toward the probe compress the wave fronts, increasing frequency, while movement away stretches them and lowers the frequency. In clinical Doppler, the sign of the shift tells you the direction of flow relative to the probe, so a higher received frequency compared to transmitted corresponds to a positive Doppler sign.