By Vvon Engineering Team | Published | Updated
Specify a film/scanner analysis system, control acquisition conditions and manage calibration, correction and constancy checks under a validated protocol.
Medical equipment RFQ checklist (TXT)
A radiochromic film measurement depends on the film, exposure, scanner and analysis protocol. When a verification result differs from expectation, investigate the complete chain rather than assuming either the treatment delivery or scanner is the cause.
Treating it as office hardware is where the errors come from.
Specify the readout system for the film and validated analysis method, including the following points.
Ask, before purchase, whether the model is available in Bangladesh with local service and whether the transparency unit is a separately supplied part. A dosimetry scanner that has to be replaced by a different model in three years means recalibrating everything, so continuity of supply is a real selection criterion.
Characterise lateral response, orientation and scanner stability for the chosen method. Positioning controls and correction models address different effects and must be assessed together.
Lateral scanner response can change with film position. Characterise it for the readout setup and use controlled positioning and any validated correction required by the method. A positioning jig improves repeatability but does not by itself eliminate spatial response variation across a large film.
Film orientation can affect scanner response. Record and reproduce orientation where required by the protocol, using clear identification before cutting. Do not assume every film design has identical orientation sensitivity.
Determine the scanner’s warm-up and repeat-scan procedure during commissioning and follow it consistently. Extra scans can also change film temperature, so an arbitrary number of discarded scans is not a substitute for a characterised protocol.
None of this survives careless handling.
Maintain calibration and verification records for the film lot, readout system and analysis method. A new lot or material/configuration change requires assessment and the appropriate calibration or validation work before clinical use.
Calibration points should span the dose range you are actually measuring, with more points where the response curve bends. Deliver them on a known geometry with a calibrated reference, scan them in the same session and the same orientation and position as the measurement films, and keep an unirradiated piece from the same batch to characterise the background.
Choose film using the current manufacturer’s intended dose range, application and response characteristics. EBT-series products and higher-dose films serve different tasks; a nominal range boundary is not an abrupt universal saturation threshold. Have the medical physicist verify the selected film and calibration across the doses actually measured.
Multichannel analysis uses the colour responses to estimate dose and address some dose-independent variation under its model. It does not remove every scanner artefact, damaged-film effect or systematic error. Validate the method and uncertainty for the intended measurements.
FilmQA Pro includes multichannel and one-scan workflows. Using suitable reference and measurement films in one scan can reduce particular inter-scan effects, but the required reference doses, timing and correction steps still apply. Follow the manual for the installed version and validate the complete workflow.
Whatever software you use, be clear about what a gamma pass rate means. It is a comparison between a measured dose distribution and a calculated one, under stated distance and dose difference criteria, over a stated region and above a stated dose threshold. Two departments quoting different pass rates may simply be using different thresholds. Record the criteria alongside the result every time, and set the criteria before you look at the answer.
Control the scanner and analysis configuration through the department’s quality system. Save acquisition settings, orientation and positioning instructions, timing rules, film identification and software versions. Coordinate updates with IT and repeat the appropriate checks after relevant changes rather than disabling security maintenance indefinitely.
Set a constancy programme with stable references, repeatability checks and documented action levels. An irradiated film’s response can continue changing with time, so rescanning an archived piece against its original value without accounting for ageing is not a reliable standalone drift test.
Manufacturer workflow reference: Ashland FilmQA Pro user guide.
For the specific correction that a validated reflection method is possible: Original study of reflection-mode EBT2 film dosimetry.
Share your application, equipment requirements and procurement timeline. Our engineers can help clarify the configuration and scope for your enquiry.