Siemens Definition AS: one collimator leaf stuck at initialization
What happened
At initialization the system reports a collimator error: one leaf moves, the other stays still and its LEDs do not change, while both F2 LEDs stay lit constantly.
What was checked
- Watched the F1/F2 LED behaviour during initialization to identify which leaf was not responding.
- Removed the gantry cover and inspected the collimator leaf drive mechanism.
Cause
The engineers found that the grease in the collimator leaf mechanism had dried out, so one leaf jammed and the initialization could not complete.
What was done
After confirming the jam, the engineers freed the stuck leaf by hand and lubricated the whole mechanism; after that the collimator initialized normally and no parts were replaced. Per the case, this mechanism is supposed to be lubricated at scheduled maintenance, and in this instance that had evidently not been done for a long time.
Safety
Isolate the scanner from power and follow the manufacturer's procedure before removing covers, never work inside the collimator while the system is energised or could start an exposure, and verify correct leaf motion and the required safety checks before returning the system to use.
Lesson: Dried-out grease in rarely serviced mechanical assemblies like collimator leaves is a common jam cause, so keep lubrication on the PM schedule instead of waiting for an initialization error.
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.