Ghost echoes are signals on the screen that look like real signals but in reality are false signals with no direct connection to an indication. Ghost echoes are usually caused by a high PRF combined with a long listening window.
- Example 1: The PRF is low and the listening window is short. Each listening window has time to close before the next one opens
- Example 2: The PRF is high and the listening window is long. The first listening window doesn’t have time to close before the next one opens
- Ghost echoes are easy to spot. They do not move like normal echoes should move. For example they move upside down when the probe is moved from right to left
- There is only one real signal and it is linked to the SDH
The cure for ghost echoes is simple. The PRF must be lowered and/or the listening window shorten.