GE Signa Avanto: occasional single spikes on MR images
What happened
Rare isolated stripe artifacts (single spikes) appearing on MR images. The QA spike test on the phantom, as reported in the case, passed only about one run in ten, usually showing one spike per test.
What was checked
- QA spike test on the phantom to confirm and characterise the artifacts (reported as passing roughly 1 run in 10).
- Humidity check in the scan room (reported at about 50%).
- Imaging with a small flex coil moved to different positions, to see whether the spike moved with the coil or stayed fixed in the image.
- Questions about ventilation and room temperature as possible sources.
- Inspection of the line filters on the RF penetration plate; the engineers found one filter damaged internally, with a coil/capacitor element torn loose.
Cause
The engineers found two contributions in this single case: mains-borne interference after a substation switching in the region, and a damaged filter on the RF penetration plate whose internal coil/capacitor connection had broken off.
What was done
The scan-room lighting wiring was replaced with shielded cable, and the damaged penetration-plate filter was repaired or replaced. When unscrewing or refitting such a filter, hold the lower nut so the body cannot rotate and tear its internal connections. After both steps the artifact disappeared and the QA spike test passed consistently.
Safety
De-energise and lock off the lighting circuit before rewiring, treat penetration-plate filter capacitors as potentially charged, follow MR static-field rules for tools in the scan room, and repeat the QA spike test before returning the system to clinical use.
Lesson: Unstable single spikes point as much to the site power history and the shield's penetration filters as to the RF chain, so ask what changed on the local grid and inspect the RF plate before blaming the scanner.
Covered in the course: MRI Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.