Which component on the spectral Doppler display represents depth?

The correct choice regarding the spectral Doppler display that represents depth is the option indicating "Depth on Y-axis." In a spectral Doppler display, the Y-axis is typically utilized to show how deep the Doppler sample volume is within the tissue or blood vessel being analyzed. This allows the clinician to assess blood flow characteristics at various depths, helping to diagnose conditions related to vascular health.

By placing depth on the Y-axis, the spectral Doppler display effectively conveys not just the velocity of the blood flow along the X-axis, which usually represents time, but also how that velocity relates to the specific depth at which it is being measured. The information can be crucial for identifying abnormalities in blood flow patterns and understanding their significance in cardiovascular assessments.

Other components such as frequency shift on the Y-axis and time on the X-axis provide important information related to the blood flow dynamics, but they do not directly indicate depth. Pixel brightness conveys intensity information related to the strength of the Doppler signal but does not represent depth either.