A comparative study of internationally used constancy testing protocols for medical X-ray imaging devices

One of the difficulties confronted by medical physicists is the variability in medical imaging device constancy testing protocols and acceptable tolerances promoted by different international standards setting and Medical Physics Professional (MPP) organizations around the world. The main focus of this study was to compare protocols and tolerances from different organizations focusing on their similarities, differences, and relative strengths and weaknesses with a view to help MPPs develop their local constancy testing protocols. The methodology that was used in this study was a comparative qualitative documentary thematic analysis of constancy testing protocols published by the International Electrotechnical Commission, European Commission, International Atomic Energy Agency, Institute of Physics and Engineering in Medicine, American Association of Physicists in Medicine and American College of Radiology. The thematic categories and labels that were analysed were: Document Metadata (Document Number, Recency, Price of Document), Equipment used in the constancy testing (Equipment required, Expense of Equipment, Ease of Availability), Measurement Protocol for constancy testing (Professional Performing the Test, Level of Complexity), Test Frequency and Tolerance Limits. From this study, the main conclusion that was drawn was that there isn’t one specific organization that publishes suitable constancy testing protocols for all the selected imaging modalities and that one often needs to garner good practice elements from more than one organization when setting up own protocols. Generic recommendations for specific imaging modalities are put forward.