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Manufacturer
Model
What This Guide Helps With
Image artifacts, calibration failures, ring artifacts, streaking, shading, or inconsistent CT image quality caused by setup, calibration, or detector-related issues.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not troubleshoot image quality issues during an active patient scan unless the scan has been safely stopped by clinical staff.
Action:
- Remove the scanner from clinical use if image quality may affect diagnosis.
- Notify CT staff that the system should not be used until the artifact is verified and corrected.
- Use another CT scanner if available.
Expected outcome:
No patient is scanned on a system producing questionable or unreliable images.
2. Verify the Reported Artifact or Calibration Issue
Confirm exactly what the user is seeing before assuming detector failure.
Action:
- Ask CT staff what type of artifact appeared.
- Check whether the issue occurred on one patient, multiple patients, phantom images, or all scans.
- Identify if the artifact appears as rings, streaks, bands, shading, noise, missing data, or reconstruction distortion.
- Review whether the issue started after warm-up, calibration, software restart, power event, tube change, service visit, or room temperature change.
Expected outcome:
The problem is clearly defined and repeatable, or isolated to a specific scan condition.
Why it matters:
Some artifacts are caused by patient positioning, metal, contrast, protocol settings, or reconstruction choices rather than detector hardware.
3. Remove Patient-Related and External Causes First
Artifacts may be caused by items in the scan field.
Action:
- Confirm the patient table, straps, immobilizers, IV poles, oxygen tubing, ECG leads, jewelry, clothing snaps, or external devices were not in the scan field.
- Ask whether the artifact appeared in the same location on multiple patients.
- If safe and appropriate, have CT staff repeat a test scan using a manufacturer-approved phantom or known-good setup.
Expected outcome:
Artifacts caused by external objects or patient setup are identified and corrected.
If this resolves the issue, document the finding and return the scanner to service after image quality is confirmed.
4. Check Scan Protocol and Reconstruction Settings
Incorrect protocol or reconstruction choices can mimic system image problems.
Action:
- Have CT staff verify the selected protocol, reconstruction kernel, slice thickness, field of view, dose settings, iterative reconstruction settings, and metal artifact reduction options.
- Compare the problematic scan to a known-good protocol.
- Check whether the issue occurs only with one protocol or all protocols.
Expected outcome:
If the issue is protocol-specific, clinical applications or CT leadership should review the protocol before equipment repair is pursued.
Why it matters:
Clinical Engineering should rule out setup and configuration issues before escalating to detector or reconstruction hardware concerns.
5. Check System Readiness and Error Messages
Detector calibration issues may be accompanied by system warnings or failed readiness checks.
Action:
- Review the scanner console for active system messages, calibration prompts, detector errors, air calibration failures, reconstruction errors, or image quality warnings.
- Record the exact message text, error code, time, and sequence of events.
- Check whether the scanner allows normal scan preparation.
Expected outcome:
Any system-generated fault is captured accurately for service documentation.
6. Confirm Gantry and Bore Are Clear
Objects inside the gantry opening can affect image quality or interfere with calibration scans.
Action:
- Inspect the gantry opening and table area for loose items, pads, positioning aids, contrast tubing, cables, cleaning materials, or covers.
- Confirm no object is blocking the scan field or contacting moving components.
- Verify the table top is clean and properly positioned.
Expected outcome:
The scan field is clear and free of external causes.
7. Verify Environmental Conditions
CT detector calibration can be affected by temperature instability or room environmental changes.
Action:
- Check whether the CT room temperature is within normal operating expectations.
- Ask staff if HVAC problems, room overheating, humidity issues, recent power loss, or room door propping occurred.
- Check for unusual heat, odors, fan noise, or blocked ventilation around system cabinets.
Expected outcome:
Environmental causes are ruled out or corrected before deeper troubleshooting.
Why it matters:
Detector systems and image calibration depend on stable environmental conditions.
8. Perform a Proper System Restart if Appropriate
Temporary software or reconstruction issues may clear after a controlled restart.
Action:
- Coordinate with CT staff to ensure the scanner is not in use.
- Follow the site-approved shutdown and startup process.
- Allow the system to fully boot and complete readiness checks.
- Do not interrupt startup, calibration, or self-test routines.
Expected outcome:
If the artifact was caused by a temporary software or communication issue, the scanner returns to normal operation.
If this resolves the issue, perform image verification before returning to service.
9. Run User-Accessible Calibration or Air Calibration Only if Allowed
Calibration should only be performed if it is part of normal operator-accessible workflow or approved Clinical Engineering procedure.
Action:
- Have qualified CT staff or authorized service personnel perform the appropriate detector calibration, air calibration, or image quality check using the approved process.
- Do not bypass service protections or perform unauthorized service-level calibrations.
- Record whether calibration passes, fails, or aborts.
Expected outcome:
Calibration completes successfully and image quality returns to normal, or the failure is confirmed for escalation.
Why it matters:
Failed calibration after external causes are ruled out may indicate detector, DAS, reconstruction, temperature, or calibration data issues.
10. Perform Phantom or Image Quality Verification
Before returning the scanner to service, image quality should be verified.
Action:
- Have CT staff perform a known-good phantom or site-approved image quality test.
- Review whether artifacts persist in the same location or pattern.
- Compare to previous acceptable image quality if available.
- Confirm no new error messages appear after calibration.
Expected outcome:
Images are clinically acceptable and artifacts are not reproducible.
If artifacts remain, remove the scanner from service.
11. Identify Artifact Pattern for Escalation
The artifact pattern can help determine the likely area of concern.
Action:
- Document whether the artifact is ring-shaped.
- Document whether the artifact is straight streaking.
- Document whether the artifact is banding.
- Document whether the artifact is shading.
- Document whether the artifact is excessive noise.
- Document whether the artifact is missing data.
- Document whether the artifact is intermittent.
- Document whether the artifact is protocol-specific.
- Document whether the artifact is present on all scans.
- Document whether the artifact is present only after warm-up.
- Document whether the artifact is present only after calibration failure.
Expected outcome:
The service vendor or imaging specialist receives useful detail instead of a vague “bad image” complaint.
12. Check for Recent Service, Updates, or Events
Recent changes often explain image quality problems.
Action:
- Ask whether there was recent PM, tube service, detector calibration, software update, power outage, HVAC work, gantry service, or protocol change.
- Review recent work orders for related CT issues.
- Check whether the artifact began immediately after one of these events.
Expected outcome:
A possible trigger is identified and included in the repair escalation.
If the Problem Persists
If image artifacts remain after patient setup, external objects, protocol settings, room conditions, restart, and approved calibration checks have been ruled out, the issue is likely internal.
The scanner should be:
- Removed from service
- Labeled Out of Service
- Escalated to Canon service, imaging service, or qualified CT support
- Held from patient use until image quality and calibration are verified
Possible internal causes may include detector calibration data failure, detector module issue, DAS communication problem, reconstruction system issue, thermal instability, or other service-level fault.
Knowing when to stop is proper troubleshooting. CT image quality problems can affect diagnosis, so do not continue scanning patients if artifact behavior is unresolved.
Clinical Use Tip
Do not troubleshoot detector artifacts on an active patient. If image quality is questionable, stop clinical use, move the patient to another scanner if available, and verify image quality with approved testing before returning the system to service.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"CT staff reported ring artifacts and failed detector calibration on the Canon Aquilion Series CT scanner during morning startup."
Cause
What was observed during troubleshooting.
Example:
"External scan field, patient setup, room conditions, protocol selection, and system restart were checked; artifact persisted during phantom verification."
Resolution
What action was taken.
Example:
"Scanner was removed from service, labeled Out of Service, and escalated to Canon service for detector calibration and image quality evaluation."
Helpful Details to Include (If Known)
- Outlet or power status checked
- Console error message or calibration failure text
- Time artifact occurred
- Artifact type and location
- Whether artifact appeared on patient images, phantom images, or both
- Whether issue affects all protocols or one protocol
- Room temperature or HVAC concerns
- Recent power outage or service activity
- Calibration passed, failed, or aborted
- System restart attempted
- Unusual heat, smell, fan noise, or cabinet alarms
- Final scanner status
- Vendor/service ticket number if escalated
Final Thought
Detector calibration and image artifact troubleshooting must stay patient-safety focused. Start with visible, external, and setup-related causes before assuming internal detector failure. If artifacts remain after basic checks and approved calibration steps, remove the scanner from service and escalate with clear documentation.
That is successful troubleshooting.