Which statement describes the difference between Doppler and B-mode frequencies when using the same transducer?

Which statement describes the difference between Doppler and B-mode frequencies when using the same transducer?

• A. The frequency for Doppler is usually lower than for imaging
• B. The frequency for Doppler is usually higher than for imaging
• C. The transmit pulse for Doppler has a greater bandwidth compared to the bandwidth for imaging
• D. The frequency for Doppler and for B-mode imaging must be identical for a given transducer

Answer: (A)

Doppler and B-mode imaging have different priorities in how we use frequency. B-mode imaging aims for the best spatial resolution to distinguish fine tissue structures, which means using a higher center frequency. Doppler, on the other hand, is all about detecting motion and penetrating to depth to sample blood flow, so a lower center frequency is preferred to reduce attenuation and improve signal from deeper vessels. Using the same transducer, this trade-off means the Doppler frequency is usually lower than the frequency used for imaging, even though Doppler shifts themselves depend on the transmitted frequency. The other statements don’t fit because imaging benefits from higher frequency and broader bandwidth for detail, Doppler doesn’t typically require greater bandwidth than imaging, and the frequencies don’t have to be identical.

Doppler and B-mode imaging have different priorities in how we use frequency. B-mode imaging aims for the best spatial resolution to distinguish fine tissue structures, which means using a higher center frequency. Doppler, on the other hand, is all about detecting motion and penetrating to depth to sample blood flow, so a lower center frequency is preferred to reduce attenuation and improve signal from deeper vessels. Using the same transducer, this trade-off means the Doppler frequency is usually lower than the frequency used for imaging, even though Doppler shifts themselves depend on the transmitted frequency. The other statements don’t fit because imaging benefits from higher frequency and broader bandwidth for detail, Doppler doesn’t typically require greater bandwidth than imaging, and the frequencies don’t have to be identical.