In which mode is the amplitude of the return echo shown as spikes along the y-axis of the image?

The mode in which the amplitude of the return echo is depicted as spikes along the y-axis is A-mode (amplitude mode). In A-mode ultrasound, each returning echo is represented as a vertical spike on a graph. The height of the spike correlates with the amplitude of the echo, indicating the strength of the reflected signal from tissue interfaces. The horizontal axis represents the depth or distance from the transducer.

This mode is primarily used for accurate measurements, such as in ophthalmology to measure the dimensions of the eye structures, but it is not common in general ultrasound imaging compared to more commonly used modes like B-mode. In B-mode, for example, the amplitude information is encoded into a two-dimensional image rather than discrete spikes, which provides a visual representation of the tissues. Understanding A-mode is crucial for grasping how ultrasound signals are processed and displayed, emphasizing the importance of amplitude in determining tissue characteristics.