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What This Guide Helps With
Addresses failed calibration or QC caused by setup, phantom positioning, environment, workflow, accessory, or system-readiness problems.
Step-by-Step Troubleshooting
1. Protect Patients From Unverified Imaging Performance
If a required QC or calibration test fails, do not assume the scanner remains clinically acceptable. Follow site policy for restricting or suspending clinical use until required performance is verified.
Expected outcome: Patients are not scanned on equipment with unverified performance.
2. Confirm the Exact Failed Test
Identify the specific calibration or QC task, the step where it failed, any displayed message, and whether the failure is repeatable.
Do not substitute a different test without understanding the failure.
Expected outcome: The failed procedure is clearly identified.
3. Verify System Readiness
Confirm that the scanner has completed startup, all required subsystems indicate ready, and no other active faults are present.
Expected outcome: QC is not failing simply because the system is not fully initialized.
4. Inspect the Phantom or Test Device
Verify the correct approved phantom or test device is being used and inspect it for visible damage, contamination, trapped material, or incorrect assembly.
Expected outcome: The test object is appropriate and physically suitable for testing.
5. Verify Phantom Positioning
Check that the phantom is positioned and centered according to the approved procedure and that table accessories or supports are not interfering.
Expected outcome: Test setup and positioning are correct and repeatable.
If correcting setup produces a passing result, document the cause and proceed to final verification.
6. Check Protocol and QC Selection
Confirm that the intended QC or calibration procedure was selected and that no unintended clinical protocol or user setting is being used.
Do not change restricted calibration values.
Expected outcome: The correct approved test workflow is being performed.
7. Check Environmental Conditions
Verify that room temperature, cooling, and equipment-room conditions are stable and that no recent HVAC or power interruption could affect system readiness.
Expected outcome: No obvious environmental condition is influencing the test.
8. Review Recent Service or Changes
Determine whether the failure began after service work, software updates, power loss, component replacement, or configuration changes.
Expected outcome: Recent events that may require qualified recalibration are identified.
9. Repeat the Approved Test Once Conditions Are Correct
After correcting confirmed setup or environmental issues, repeat the appropriate approved QC test.
Avoid repeated calibration attempts when the same failure persists.
Expected outcome: The system passes the required verification test.
If it passes and all required performance checks are acceptable, troubleshooting is complete.
10. Escalate Repeated Calibration or QC Failure
If the test continues to fail, remove or restrict the CT system according to site policy and escalate. Do not perform restricted detector, geometry, dose, or service calibration without appropriate authorization and equipment.
Expected outcome: A scanner with unverified performance is not returned to unrestricted patient use.
If the Problem Persists
Common external and setup causes have been ruled out. Remaining possibilities may include detector calibration, X-ray output, mechanical alignment, acquisition electronics, image processing, environmental compensation, or service-level configuration.
The CT scanner should be:
- Removed from service or clinically restricted as appropriate.
- Labeled Out of Service when required.
- Sent for repair or qualified service evaluation.
- Evaluated using appropriate Canon procedures, phantoms, and approved measurement equipment.
- Calibrated, repaired, or configured only by qualified personnel.
All required QC and regulatory or institutional performance checks must pass before return to service.
Knowing when to stop external troubleshooting is proper troubleshooting.
Clinical Use Tip
A failed QC test is a performance-verification problem, not merely an inconvenience; do not clear the device based only on a normal-looking clinical image.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"CT staff reported a routine image-quality QC test would not pass."
Cause
What was observed during troubleshooting.
Example:
"Clinical Engineering found the approved phantom was positioned off-center during the test."
Resolution
What action was taken.
Example:
"Repositioned the phantom correctly, repeated the approved QC procedure, and confirmed the required test completed successfully."
Helpful Details to Include (If Known)
- Exact QC or calibration test.
- Exact failure message.
- Phantom identification and condition.
- Phantom positioning.
- Protocol or test selection.
- Environmental conditions.
- Recent service or software change.
- First and repeat test results.
- Any restrictions placed on clinical use.
- Final scanner status.
Final Thought
Treat failed QC as a patient-safety concern, verify setup and environment before assuming internal failure, and require successful objective testing before returning the scanner to service.
That is successful troubleshooting.