Understanding the commissioning process for a new CT simulator

A new CT simulator becomes clinically useful only after its images, radiation output, geometry and software have been tested against clearly defined requirements. Commissioning is the structured process that demonstrates the system is safe, accurate and suitable for radiation therapy planning, rather than simply confirming that the scanner can acquire diagnostic-quality images.

For an Australian oncology service, the work usually involves a medical physicist, radiation oncologists, radiation therapists, radiographers, engineers, information technology staff and the vendor’s application specialists. The project must also fit state or territory radiation regulations, local clinical workflows and the realities of integrating a CT simulator into an existing treatment-planning network.

Define the clinical and technical scope

Commissioning starts before installation. The team should document how the scanner will be used, including routine planning CT, contrast studies, four-dimensional CT, respiratory gating, paediatric imaging, stereotactic treatments and any specialised immobilisation. The intended patient load, scan protocols, planning-system requirements and acceptable downtime should be agreed in advance.

A useful specification covers the bore size, tabletop, indexing system, laser arrangement, couch travel, gantry tilt, injector, respiratory equipment and image reconstruction options. It should also identify the required DICOM services, CT-to-density calibration method and compatibility with the treatment-planning system. Reviewing the conference archive can provide useful historical context on how professional medical physics meetings discuss imaging, quality assurance and clinical implementation.

The site acceptance process should distinguish vendor responsibility from the hospital’s commissioning responsibility. Acceptance testing establishes that the equipment meets the purchase specification and manufacturer claims. Commissioning then determines whether it performs adequately for the service’s actual clinical applications.

Check the room, geometry and safety systems

Before scanning patients, inspect the physical environment. Confirm electrical supply, cooling, ventilation, network connections, radiation shielding, emergency power and equipment clearances. The room should support safe patient transfer and allow staff to work around immobilisation devices without obstructing the gantry or lasers.

Radiation protection checks should be completed under the relevant Australian state or territory requirements, with advice from the responsible radiation safety expert. ARPANSA guidance may inform the approach, but licensing and notification arrangements differ between jurisdictions such as New South Wales, Victoria and Queensland. A local service should retain signed survey reports, shielding records, warning-light checks and interlock tests in its quality system.

Geometric accuracy is particularly important because the CT image defines the patient coordinate system used for treatment planning. Test the tabletop position, couch indexing, scan-plane location, laser coincidence, gantry indicators and external reference marks. A small systematic error can transfer directly into treatment setup, so measurements should be made with calibrated tools and repeated after any major service intervention.

Establish image quality and dose performance

The commissioning team should evaluate uniformity, noise, contrast resolution, spatial resolution, artefacts, slice thickness, image location and CT number stability. Measurements need to cover the protocols used for different body regions and patient sizes, not merely the manufacturer’s default adult abdomen protocol.

CT numbers must be sufficiently stable for the conversion of image values into electron density or mass density used by the treatment-planning system. This calibration should use an appropriate phantom and should be repeated across relevant tube potentials, reconstruction methods and field sizes. If the service plans to use metal implants, contrast enhancement or paediatric protocols, those situations should be assessed explicitly.

Dose assessment should include volume CT dose index, dose-length product and the protocol settings that generate them. In Australia, imaging teams commonly compare local practice with diagnostic reference levels and monitor trends through a documented quality assurance programme. A CT simulator may require a different balance between image quality and dose from a diagnostic scanner, but lower dose must never compromise target definition or treatment-planning confidence.

Artefacts deserve practical attention. Shoulder streaks, dental fillings, hip prostheses, respiratory motion and patient movement can affect contouring and dose calculation. The team should record mitigation strategies, such as iterative reconstruction settings, immobilisation, breath-hold instructions or alternate acquisition protocols.

Validate treatment-planning integration

A CT simulator is part of a larger digital chain. Test patient registration, image transfer, DICOM headers, orientation, slice spacing, pixel dimensions, couch coordinates and series selection. Images should move reliably from the scanner to the oncology information system and treatment-planning system without manual workarounds that could introduce transcription errors.

End-to-end testing should include structure sets, planning images, dose calculations and export of the resulting treatment data. Verify that the treatment-planning system applies the correct CT-density table and that the chosen reconstruction kernel does not produce an unsuitable calibration. If a new scanner replaces an older unit, compare representative cases and review any change in calculated dose or contour appearance.

Four-dimensional CT requires additional validation of respiratory signals, phase sorting, motion artefacts and reconstructed phase integrity. For gated treatments, confirm that the signal reaches the planning and treatment systems in the expected format. Contrast protocols should be tested with the injector, emergency procedures and documentation requirements included in the workflow.

Australian services often operate across metropolitan and regional networks, with images shared between public hospitals, private clinics and outreach locations. Network latency, vendor support hours and responsibility for troubleshooting should therefore be tested realistically. A protocol that works in a vendor demonstration may fail when the service is busy, the PACS is under load or a regional site is relying on remote support.

Turn measurements into safe clinical practice

Commissioning is incomplete until staff can use the system consistently. Radiation therapists and radiographers should receive training on scan protocols, immobilisation, patient positioning, contrast safety, respiratory procedures, artefact management and recovery from interrupted scans. Radiation oncologists should review image quality and target visualisation, while physicists confirm that the technical limits are understood.

Create a controlled protocol library with approval dates, owners and revision history. It should identify scan range, pitch, tube voltage, tube current modulation, reconstruction series, slice thickness, contrast timing and patient instructions. Clear naming conventions reduce the risk of selecting a diagnostic series when a planning series is required.

The quality assurance schedule should separate daily, monthly and annual tasks. Daily checks might include lasers, tabletop indexing, image transfer and basic image quality. Periodic testing can cover CT numbers, uniformity, noise, spatial resolution, dose output, geometric accuracy and respiratory equipment. Define action levels before clinical use, including who investigates a failure and when the scanner must be removed from service.

Keep a commissioning report that explains methods, equipment serial numbers, calibration status, results, tolerances, deviations and approval signatures. Include baseline images and trend data so future physicists can distinguish gradual drift from a genuine fault. The event contact page also illustrates the value of maintaining clear ownership and contact details for technical and professional coordination.

A practical Australian implementation should account for public-hospital procurement cycles, vendor availability and state-based compliance reviews. Schedule application training and acceptance testing with enough time for engineering changes, and avoid opening the service on a Friday afternoon simply because the installation date has arrived. Allowing a proper validation period is usually cheaper than correcting a workflow error after patients have been scanned.

Bring the commissioning plan into the project meeting, assign each test to a named person and require documented sign-off before clinical release. Once the CT simulator is in service, review its performance through routine QA, incident learning and periodic protocol audits. That disciplined approach turns a new scanner into a dependable part of radiation oncology rather than an expensive imaging device awaiting confidence.