Philips Intera 1.5T: DWI sequence aborts partway through
What happened
On this 1.5T scanner the DWI sequence stopped consistently at a reported 10% of the run, right where the gradient reached the reported 274 degrees. The engineers found the failure reproduced with different coils and connectors, so the receive chain was unlikely to be the culprit.
What was checked
- Swapped coils and connectors first — as reported in the case, nothing changed.
- Checked the coil and gradient cables for insulation breakdown.
- Replaced the modulator and the gradient control boards; the fault persisted.
- Powered down, disconnected and measured the capacitors along the sides of the gradient cabinet with an RLC meter.
- Pulled a gradient dump — the logs gave no pointer to the cause.
- Compared the PDM block address settings in the gradient cabinet against the manufacturer's service documentation and found a mismatch.
Cause
The hardware addresses of the PDM blocks were set incorrectly, not matching the documentation. Under the heavy gradient demand of diffusion imaging this misconfiguration aborted the sequence — and, as the engineers found, the logs did not flag it.
What was done
The PDM block addresses were re-set to the values specified in the manufacturer's service documentation — a procedure done by authorised personnel. After that the DWI sequence ran to completion; the outcome is reported as solved.
Safety
The gradient cabinet stores dangerous energy in its capacitors: before any work inside, power down, follow the manufacturer's lockout and discharge procedure, and verify with a meter that the capacitors are discharged before touching anything.
Lesson: When a fault ignores coil swaps and the logs stay clean, go back and verify basic hardware configuration and addressing against the documentation before replacing components.
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.