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Manufacturer
Model
What This Guide Helps With
Troubleshooting detector head motion, positioning, collision avoidance, proximity sensor, or gantry movement faults before repair escalation.
Step-by-Step Troubleshooting
Ensure Patient Safety First
Confirm the patient is not in contact with the detector heads, table, gantry, or any moving part of the system.
If the issue occurs during a patient setup or acquisition, stop motion and have clinical staff safely remove or reposition the patient according to site policy.
Expected outcome: No patient is exposed to unintended detector, table, or gantry movement.
Confirm the Exact Motion or Positioning Complaint
Ask the operator what motion failed and when it occurred. Determine whether the issue involves:
- Detector head will not move
- Detector head stops during positioning
- Detector head position does not match the selected protocol
- Proximity or collision warning appears
- Gantry rotation is inhibited
- Detector orbit fails during acquisition
- Table and detector alignment issue
- Intermittent fault during setup only
Expected outcome: The problem is narrowed to detector motion, gantry rotation, table positioning, or proximity/collision sensing.
Check for Obvious Physical Obstructions
Inspect the detector head travel area, table area, gantry clearance, patient accessories, straps, cables, positioning aids, and nearby equipment.
Remove anything that could block detector movement or trigger collision protection.
Expected outcome: Motion path is clear and no external object is causing the fault. If this resolves the issue, stop.
Verify the Patient Table Position and Accessories
Confirm the table is properly positioned, locked, and not extended or angled in a way that conflicts with detector movement.
Check that headrests, arm supports, straps, cushions, or patient positioning devices are not protruding into the detector path.
Expected outcome: The table and accessories do not interfere with detector head travel.
Check Detector Head Clearance and Starting Position
Confirm both detector heads are in a safe starting position and are not already close to the table, patient area, or gantry structure.
Use operator controls only as intended and avoid forcing motion.
Expected outcome: Detector heads have adequate clearance for the selected motion.
Review the System Message or Error Code
Read the message on the acquisition console or system control interface. Note whether the fault references:
- Detector head motion
- Gantry rotation
- Collision detection
- Proximity sensor
- Limit switch
- Table interlock
- Positioning timeout
- Motion controller or drive fault
Expected outcome: The displayed fault gives direction before parts or internal failures are assumed.
Confirm Emergency Stop and Safety Interlocks Are Released
Check that all emergency stop buttons are released and that any required covers, doors, or interlocked access points are properly closed.
Reset only according to normal operator procedure.
Expected outcome: Motion is not being inhibited by an active emergency stop or external safety interlock.
Check Hand Controller, Gantry Controls, and Operator Input
Verify whether the issue occurs from one control point or all control points.
If motion fails only from one pendant, hand control, or control panel, inspect that control for stuck buttons, damage, loose cable connection, or liquid intrusion.
Expected outcome: A local control issue is separated from a system-wide motion fault.
Attempt a Normal Repositioning Sequence When Safe
With no patient present and the area clear, have qualified staff attempt a normal detector or gantry repositioning sequence using standard controls.
Do not repeatedly command motion if the system stops, alarms, or behaves unpredictably.
Expected outcome: Motion either completes normally or the fault repeats in a controlled, patient-free condition.
Check Whether the Fault Follows a Specific Motion
Determine whether the issue occurs during:
- One detector head movement
- Both detector heads
- Gantry rotation
- Table movement
- Detector approach toward the patient area
- Only one study protocol
- All positioning attempts
Expected outcome: The failure pattern helps identify whether the issue is localized or system-wide.
Check for Recent Changes or Service Activity
Ask whether there were recent room changes, table service, detector service, software updates, power events, cleaning, collision events, or accessory changes.
Expected outcome: Recent changes are identified as possible contributors to motion or proximity sensor behavior.
Perform a Controlled Power Restart Only If Appropriate
If the system is idle, no patient is present, and site procedure allows it, perform a normal shutdown and restart of the acquisition system and gantry control system.
Do not use power cycling to repeatedly clear an active mechanical or safety fault.
Expected outcome: Temporary communication or software-related motion lockout clears. If the fault returns, continue escalation.
Verify Room Power and Environmental Conditions
Confirm the system has stable power and that no room equipment, carts, cables, or floor obstructions are affecting gantry or table movement.
Look for unusual heat, odor, sounds, vibration, or visible damage near the gantry or detector assembly.
Expected outcome: External power, environment, and room setup are not contributing to the fault.
Do Not Bypass Proximity or Collision Protection
Do not tape, defeat, disable, or bypass proximity sensors, collision sensors, limit switches, or safety interlocks.
These protections are part of patient and staff safety.
Expected outcome: Safety systems remain intact while troubleshooting is performed.
Determine Whether the System Can Be Safely Returned to Use
If the detector head, gantry, and table move normally with no repeated alarms, no abnormal sounds, and no safety warnings, follow site policy for functional verification before clinical use.
If any motion fault repeats, motion is inconsistent, or a proximity warning appears without clear cause, remove the system from service.
Expected outcome: The system is either verified safe for use or escalated appropriately.
If the Problem Persists
If detector motion, gantry positioning, or proximity sensor faults continue after external obstructions, table setup, controls, emergency stops, interlocks, and restart conditions have been checked, the issue is likely internal.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for repair or bench/vendor evaluation
Possible internal causes may include a failed motion drive, encoder, limit switch, proximity sensor, collision detection circuit, control board, cabling fault, or gantry/table motion subsystem issue. Do not continue repeated motion attempts or bypass safety protections.
Knowing when to stop is proper troubleshooting.
Clinical Use Tip
Do not troubleshoot detector motion or proximity faults with a patient under the detector heads. Move the patient away from the system first, then test motion only when the gantry, table, and detector area are clear.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Nuclear Medicine reported the Symbia Evo detector head stopped during patient positioning and displayed a proximity/collision warning."
Cause
What was observed during troubleshooting.
Example:
"Verified no patient was present, checked detector travel path, table position, accessories, emergency stops, and operator controls; fault repeated with clear motion path."
Resolution
What action was taken.
Example:
"Removed Symbia Evo from service, labeled Out of Service, documented repeated detector motion/proximity fault, and escalated for vendor evaluation."
Helpful Details to Include (If Known)
- Whether a patient was present when the issue occurred
- Exact error message or fault code
- Which detector head was affected
- Whether gantry rotation, table motion, or detector motion failed
- Whether the fault occurred during setup, acquisition, or QC
- Accessories or positioning aids in use
- Emergency stop status
- Obstructions found or not found
- Whether issue occurred from one control station or all controls
- Abnormal sounds, vibration, heat, or smell
- Restart attempted and result
- Final device status
Final Thought
Detector head motion and proximity faults must be handled carefully because they involve moving components near the patient. A logical approach starts with patient safety, then rules out obstructions, table setup, accessories, controls, and interlocks before assuming internal failure. Clear CCR documentation helps repair teams understand whether the fault was environmental, operator-control related, or a repeatable system problem.
That is successful troubleshooting.