Siemens SOMATOM Sensation: progressive detector module failure
What happened
Detector signals were degrading channel by channel on the trend graph. Modules began failing one after another over several months, and after a long idle period the failures spiked.
What was checked
- Opened the detector block and inspected it visually — the engineers found it clean, with no contrast fluid contamination.
- Inspected the collimator — clean, no visible problems.
- Analysed the event log and mapped the module failures over time to see the pattern.
- Plotted signal levels per module to localise the degraded ones.
Cause
The engineers' working theory is age-related detector degradation, aggravated by temperature swings during the prolonged shutdown, when the room climate control was apparently switched off. This is the probable cause, not a confirmed one.
The cause is probable and was not fully confirmed.
What was done
Replacement of the faulty detector modules — the signal graph was used to decide exactly which modules to swap. As reported in the case, the outcome was considered probable rather than fully confirmed.
Safety
De-energise the scanner and let the internal electronics settle before opening the detector housing, and complete the manufacturer's calibrations and checks, including image quality and electrical safety verification, before the unit returns to clinical use.
Lesson: Per-module signal trend graphs are a practical way to localise degrading detector modules, and room climate control must stay on even during long shutdowns because thermal stress accelerates detector ageing.
Covered in the course: CT 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.