What in the Heck is that Noise?
One of the most frequent, and difficult, problems we encounter in ultrasound service are related to noise in images. This can occur in 2D, color Doppler (CD), pulsed wave Doppler (PW) or continuous wave Doppler (CW). Finding and eliminating the source of the noise can involve some detective work and out-of-box thinking.
As with all troubleshooting, the process of elimination is employed. Begin by isolating the system and any device attached to it.
Does this noise only occur with a specific probe? If so, replace it and confirm the problem has been resolved.
Does it occur with a specific port? Try another one.
Verify that the ground is intact by performing a ground continuity test and ensure all system covers and shielding are making good contact and have clean contact surfaces. Are there any peripherals connected to the system via power, video, network or RS232 cables? Disconnect them one at a time to see if the noise disappears.
If the noise is still present, we must now look outside of the system and into the environment it resides in. Are there any devices in the room that may be on the same circuit such as gel warmers, fans, fluorescent lights, coffee makers, clock radios, etc.? Try unplugging or turning them off one at a time to see if the noise is eliminated.
Perhaps the noise is the result of noisy power or emission by some device close by. Try to move the system to another part of the facility and verify whether the noise is still present. I once worked on a noise problem that was intermittent and it turned out that every time the elevator passed the floor the system was on, noise would be induced into the image.
The facility ground may be the culprit as well. Even though you have a solid ground circuit from the system to the wall, how is the ground from the wall to earth ground? I had another system noise issue where I suspected a bad ground so I connected a car jumper cable from the system ground to the cold water pipe of the sink in the exam room and the noise disappeared. It turned out that the building ground was poor and the solution was to take a garden hose and trickle it on the ground pipe for the building overnight (true story).
If the noise persists, the problem may be internal circuit boards or power supplies so troubleshoot accordingly. Image noise issues can be extremely difficult to isolate, but by following the basic troubleshooting steps outlined here you can make the task substantially easier.