Compared to grayscale B-mode, color Doppler has what characteristic regarding axial resolution?

Compared to grayscale B-mode, color Doppler has what characteristic regarding axial resolution?

• A. Higher axial resolution
• B. Similar axial resolution
• C. Lower axial resolution
• D. Variable axial resolution depending on depth

Answer: (C)

Axial resolution is how well we can distinguish two structures that lie along the path of the ultrasound beam, and it depends on the length of the transmitted pulse. Grayscale B-mode uses short, high-bandwidth pulses, so it provides very good axial detail. Color Doppler, on the other hand, needs to detect and quantify flow by sending multiple pulses per line and using Doppler processing to estimate velocity. That requires a longer effective pulse sequence and larger sampling gates (ensemble length), which blurs detail along the beam and reduces axial resolution compared with grayscale. So color Doppler has lower axial resolution. The other options would imply equal, higher, or depth-dependent resolution, which doesn’t align with how color Doppler’s velocity estimation trade-offs axial sharpness for Doppler information.

Axial resolution is how well we can distinguish two structures that lie along the path of the ultrasound beam, and it depends on the length of the transmitted pulse. Grayscale B-mode uses short, high-bandwidth pulses, so it provides very good axial detail. Color Doppler, on the other hand, needs to detect and quantify flow by sending multiple pulses per line and using Doppler processing to estimate velocity. That requires a longer effective pulse sequence and larger sampling gates (ensemble length), which blurs detail along the beam and reduces axial resolution compared with grayscale. So color Doppler has lower axial resolution. The other options would imply equal, higher, or depth-dependent resolution, which doesn’t align with how color Doppler’s velocity estimation trade-offs axial sharpness for Doppler information.