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What This Guide Helps With
Troubleshooting PET daily QC, detector normalization, calibration, or sensitivity-related failures using safe external checks before service escalation.
Step-by-Step Troubleshooting
Ensure Patient Safety First
Confirm no patient is on the PET/CT table or scheduled for immediate scanning on the affected system.
If the PET daily QC or detector calibration failed before patient imaging, do not proceed with clinical PET acquisition until QC status is acceptable per site policy.
Expected outcome: Patient imaging is not performed on a PET system with unresolved calibration or detector readiness concerns.
Confirm the Exact Failed Process
Ask the technologist or physicist which process failed and when it failed.
Identify whether the issue involves:
- PET daily QC failure
- Detector normalization failure
- Calibration failure
- Blank scan or source-related QC failure
- High count-rate variation
- Detector block or ring error
- SUV, sensitivity, or uniformity concern
- Failure after startup, reboot, service, or environmental change
Expected outcome: The failure type is clearly identified before troubleshooting continues.
Review the System Message and QC Result
Check the operator console or syngo workstation for the displayed error message, failed test name, detector warning, or QC result summary.
Record whether the failure points to a detector, source, acquisition, motion, environmental, or processing issue.
Expected outcome: The reported failure is documented accurately instead of described only as “PET QC failed.”
Verify the System Is Not in an Unsafe or Incomplete Startup State
Confirm the Biograph mCT completed normal startup and that PET, CT, gantry, table, acquisition computer, and workstation functions are available.
If the system recently restarted, allow the normal initialization process to complete before repeating QC.
Expected outcome: QC is not being attempted while the system is still initializing or partially unavailable.
Check Room and System Environmental Conditions
Verify the PET/CT room temperature and humidity are within the facility’s normal imaging room range.
Look for recent HVAC issues, temperature swings, water leaks, unusual heat, or airflow obstruction around system cabinets.
PET detector performance can be sensitive to environmental instability.
Expected outcome: No obvious room condition is contributing to detector or calibration instability.
Confirm No Obstruction or Unapproved Object Is in the PET Bore
Inspect the scanner bore, patient table, table pad, head holder, positioning aids, straps, coils, and accessories.
Remove any non-required items before QC or calibration.
Expected outcome: Nothing in the field of view is interfering with PET QC, blank scan, normalization, or calibration activity.
If removing the obstruction resolves the issue after repeating the appropriate QC, stop troubleshooting.
Verify the Patient Table Is Properly Positioned
Confirm the table moves normally, indexes correctly, and is positioned according to the QC or calibration workflow.
Check for table limit messages, positioning errors, or incomplete table travel.
Expected outcome: PET QC is not failing because the table is mispositioned, blocked, or not reaching the expected scan position.
Check the PET Calibration or QC Source Setup
If the workflow uses a PET calibration, normalization, or QC source, confirm the correct source is available, seated, and handled according to site radiation safety policy.
Do not handle radioactive sources unless authorized and trained under the facility’s radiation safety program.
Expected outcome: The correct source and setup are confirmed by qualified staff.
Confirm Source Identity, Activity, and Expiration Status With Qualified Staff
Ask Nuclear Medicine, Physics, or Radiation Safety to confirm that the expected source is not expired, decayed below usable activity, incorrectly selected, or mismatched to the QC workflow.
Low activity, wrong source selection, or expired calibration data can cause QC or normalization failures.
Expected outcome: Source-related causes are ruled out by qualified personnel.
Verify the Correct QC or Calibration Workflow Was Selected
Confirm the technologist selected the correct daily QC, normalization, calibration, or blank scan procedure for the Biograph mCT.
Check whether the wrong protocol, incorrect scanner configuration, or wrong source option was selected.
Expected outcome: The failure is not caused by an incorrect operator workflow selection.
Check for Recent Service, Software, or Configuration Changes
Ask whether any recent service activity, software update, detector calibration, PET electronics work, network change, or workstation change occurred.
A failure immediately after a change may indicate the system requires vendor-level verification or recalibration.
Expected outcome: Recent changes are identified and included in escalation notes.
Inspect External Cables and Accessible Connections
Without opening system covers, visually inspect accessible workstation, acquisition computer, gantry-side, and network connections.
Look for disconnected cables, loose network patch cords, damaged connectors, tripped power strips, or disturbed equipment after cleaning or service.
Expected outcome: No obvious external disconnection is causing PET acquisition, processing, or detector communication failure.
If reconnecting an obvious external cable restores communication and QC passes, document the correction and stop.
Check Workstation and Acquisition Computer Status
Confirm the acquisition computer and syngo workstation are powered, responsive, logged in correctly, and not displaying storage, database, application, or communication errors.
PET QC can fail if acquisition data is collected but not processed correctly.
Expected outcome: The PET acquisition and processing chain is available.
Check for DICOM, Storage, or Disk Space Warnings
Review whether the workstation reports low disk space, archive queue errors, database errors, or failed image storage.
While not always the root cause of detector QC failure, processing and storage problems can interrupt QC completion.
Expected outcome: The QC failure is not caused by a workstation storage or processing limitation.
Repeat the QC Only When Safe and Appropriate
After external setup, source, room, table, and workstation checks are complete, have qualified imaging staff repeat the appropriate QC or calibration workflow.
Do not repeatedly run failed calibration routines without physics or vendor guidance.
Expected outcome: The test either passes after correcting an external condition or fails consistently with a documented symptom.
Review for Repeating Detector or Ring Failure Patterns
If the repeated test fails, note whether the same detector block, ring, module, or channel is repeatedly identified.
A repeatable detector-specific failure is more likely to require Siemens service evaluation.
Expected outcome: The failure pattern is documented for escalation.
Do Not Attempt Internal Detector or Electronics Repair
Do not open PET gantry covers, reseat internal detector electronics, adjust calibration files, modify normalization data, or perform internal board-level troubleshooting unless authorized and trained for that system.
Expected outcome: Troubleshooting remains within safe Clinical Engineering limits.
If the Problem Persists
If the PET detector normalization, calibration, or daily QC failure remains after external checks, source verification, room condition review, table positioning checks, and workstation status checks, common external causes have been ruled out.
The issue may involve PET detector modules, normalization data, acquisition electronics, calibration files, source handling parameters, environmental stability, or vendor-level service requirements.
The device should be:
- Removed from clinical PET service
- Labeled Out of Service
- Escalated to Siemens service, qualified imaging service, or medical physics for bench/system evaluation
Knowing when to stop is proper troubleshooting. Repeated failed PET QC should not be bypassed for patient imaging.
Clinical Use Tip
Do not troubleshoot PET detector calibration or daily QC issues during an active patient scan. Move the patient to another approved imaging workflow first, and involve Nuclear Medicine, Physics, and Radiation Safety when source-based QC or calibration is involved.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Nuclear Medicine reported that the Siemens Biograph mCT failed PET daily QC with a detector normalization/calibration error before patient imaging."
Cause
What was observed during troubleshooting.
Example:
"External checks found no bore obstruction, table positioning issue, workstation fault, or obvious source setup problem; repeat QC continued to fail with the same detector-related message."
Resolution
What action was taken.
Example:
"Removed PET/CT system from clinical PET service, labeled unit Out of Service, documented QC failure details, and escalated to Siemens service and medical physics for further evaluation."
Helpful Details to Include (If Known)
- Exact PET QC, normalization, or calibration test that failed
- Error message or detector/ring/module reference
- Whether the issue occurred before patient scanning
- Whether CT side remains operational
- Room temperature or HVAC concerns
- Source type, activity status, and expiration confirmation by qualified staff
- Whether table movement and indexing were normal
- Whether any object was found in the bore
- Whether workstation or acquisition computer errors were present
- Whether a reboot or repeat QC was attempted
- Whether the same detector area failed repeatedly
- Recent service, software, or environmental changes
- Final device status
Final Thought
PET detector QC and calibration failures should be approached carefully and logically. Clinical Engineering can rule out external setup, source, table, workstation, and environmental issues, but repeated detector or normalization failures require appropriate escalation. Patient safety, physics involvement, and clear CCR documentation are more important than forcing the system back into service.
That is successful troubleshooting.