1. System Restart

• Reboot each CT system, ideally during low-usage early morning hours, so all components start from a known clean state.
• Confirm gantry, table, console, and network/PACS connections are all responding normally before proceeding.

2. X-ray Tube Warm-Up

• Select the tube warm-up (Tube/OLP) protocol on the console.
• The sequence runs several low-energy exposures, incrementally raising mA and kV so the anode heats gradually and evenly.
• Leave the specified pause (typically 30-60 seconds) between exposures - this prevents thermal shock to the tube.
• Watch the system indicators until it confirms "warm-up complete." Skipping this step risks tube damage and can lead to very costly repairs (tube replacement can run well into six figures) and unplanned downtime.

3. Daily QC Phantom Scan (ACR-aligned)

• Center the ACR (or vendor) phantom in the scan field of view (SFOV), using the smallest slice thickness allowed by the max N x T.
• Measure water CT number and standard deviation - required daily.
• Perform artifact evaluation over the phantom FOV - required daily (use axial and helical mode on alternating days if your QC manual allows, to speed the process).
• At least monthly: an air scan with the largest clinical SFOV, viewed at ~100 HU window width / -1000 HU window level, to check for artifacts outside the phantom FOV.

4. Additional Periodic Checks (not daily, but worth confirming they're current)

5. Documentation

• Log results on the CT Equipment Quality Control Data Form for that specific machine.
• If any value falls outside control limits, flag it, stop clinical use of that unit, and route to the Qualified Medical Physicist (QMP) or service engineer for corrective action before scanning patients.
• Keep per-machine records so preventive maintenance and any post-repair QC (re-baseline required after tube or detector service) are traceable.

Running this across 4 machines

• Stagger warm-up start times (e.g., 5-10 min apart) if power/network load is a concern, but each unit needs its own independent warm-up and QC run - you cannot skip it because a neighboring scanner already warmed up.
• Assign one technologist (or a rotation) as responsible for daily QC per unit, per ACR continuous QC program requirements, and have a QMP review results at least annually or sooner if failures occur.

CT Room Environmental Requirements: Humidity

• Below 30% humidity: risk of static electricity buildup, which can damage sensitive electronics or cause artifacts.
• Above 60-70% humidity: risk of condensation forming on high-voltage components (tube, generator connectors), which can trigger short circuits or arcing.
• Rapid fluctuations in humidity are actually more damaging than a stable value at the edge of the range - sudden swings cause condensation even within the "acceptable" band.
• For PET/CT specifically, humidity and temperature swings can also affect crystal/PMT performance and show up as count-rate deficits in image quality, not just hardware failures.

• Confirm each scan room's HVAC log/thermostat shows humidity within your manufacturer's specified band (check each vendor's manual - GE, Siemens, Philips, Canon each have slightly different tolerances) before running daily QC.
• If your facility has a building management system (BMS), pull the overnight humidity/temperature trend for each room, not just the current reading, since transient spikes (e.g., an HVAC outage overnight) can still have caused condensation even if the morning reading looks normal.
• Document out-of-range readings the same way you'd document a failed QC phantom result, and hold that unit from clinical use until verified safe.