Which image demonstrates appropriate spectral Doppler gain?

Option B demonstrates appropriate spectral Doppler gain. Appropriate gain settings ensure that the Doppler signal is adequately amplified without introducing excessive noise or artifacts. In Option B, the spectral waveform is clearly visible with distinct borders, and the background noise is minimal. In contrast, other options might show either under-gained (too little signal) or over-gained (excessive noise and signal) images, making it difficult to accurately interpret the spectral Doppler information.References:

ARDMS Sonography Principles and Instrumentation guidelines

"Understanding Ultrasound Physics" by Sidney K. Edelman