Interlaboratory comparisons of the physical properties of X-ray systems and display devices in clinical conditions: whether it relates to how well we measure

Abstract Introduction: Polish Atomic Law requires that organizations conducting quality control checks on medical radiological equipment must participate in interlaboratory comparisons. Medical physicists who conduct these tests in their hospitals seek to validate their results by participating in interlaboratory comparisons (ILC) at least once every four years. Material and methods: Comparisons involved measurements of physical parameters for various medical imaging equipment, including a digital X-ray unit, an angiograph, a computed tomography scanner, and a display device used to present medical images. The reference value was defined as the weighted average of the measurements performed by the participants. The En index calculation was used to assess the measurement results of each participant individually. Results: All laboratories achieved 100% satisfactory results for computed tomography, angiography, and X-ray diagnostics, despite using mostly different research methods and various measuring equipment. During the ILC, we observed discrepancies in the results of Hounsfield Unit (HU) measurements in computed tomography (CT), which were due to the size and position of the region of interest (ROI). Additionally, there were discrepancies in the results of dose measurements in angiography, attributed to factors such as the influence of the patient’s table on the measurement and the value of the backscatter factor. As a result, a standard measurement method was established. For display device measurements, two laboratories achieved 100%, two achieved over 94%, and one achieved over 88%. Conclusions: The goals for conducting comparative research in the field of X-ray diagnostics have been met. The participants’ proper use of the measuring equipment has been confirmed, and the suitability of the research methods for the intended purpose has been verified. We identify potential sources of discrepancies during ILC conducted in clinical settings. Selecting the appropriate measurement geometry and testing procedures is crucial for obtaining valuable ILC results.