60 Hz Noise in Ultrasound Images

The most common noise found in ultrasound systems is caused by 60Hz interference and is seen as radial spokes in the patient image area of the screen only. Streaks or spokes are formed radially from the near to far field and may be steady, jumping around or intermittent. I have found several sources of this noise, the most obvious being an open ground in the power cord. This noise can also be caused by a broken shield connection in the transducer cable, which can be often be verified by moving the cable and watching for appearance or disappearance of the noise. A defective ballast in a fluorescent light fixture in the room can also cause this problem, look for it if the noise shows up only when the machine is in a specific area. The most interesting one was in a GE RT3200, where I found the wires to the AC powered cooling fans were routed too close to the front-end circuits, rerouting the wires fixed the problem. In these cases the noise originated before the scan converter, in the front-end of the system. If you see horizontal black bars or waves floating through the entire screen, you have 60Hz noise in the back end of the system. This problem is usually in the monitor (check for its presence on a hardcopy) and probably caused by a leaking or open power supply filter capacitor.