What axis on a B-mode image represents the amplitude of echo signals?

In a B-mode (brightness mode) ultrasound image, the z-axis represents the amplitude of the echo signals received from the tissues. In a typical graphical representation of ultrasound data, the x-axis usually corresponds to the lateral position (depth), while the y-axis generally represents the depth of the structures being imaged.

The z-axis, which is not typically displayed on a two-dimensional plane but rather implies brightness or intensity, indicates the strength or amplitude of the echoes returning from the tissues. This amplitude directly correlates to the echogenicity of the tissues, meaning that brighter areas on the image correspond to stronger echo signals (higher amplitude), while darker areas represent weaker echoes (lower amplitude).

Understanding this concept is crucial as it helps sonographers interpret images correctly in relation to the anatomical structures being examined.