Calibration services for X-ray multimeters in Europe: current situation and future needs

Introduction: Optimization and quality control of the diagnostic and interventional radiology procedures is usually performed with an X-ray multimeter (XMM) based on the non-invasive measurements of different X-ray tube and output parameters obtained from the X-ray beam, such as air kerma, tube voltage and half-value layer. Standardization and metrological support need to be improved, and harmonized calibration procedures are not available for all quantities. There is also a lack of data on performance of XMMs in different measurement conditions relevant for clinical practice. Methods: The needs for calibration of XMMs and current state of the art of calibration services were investigated by performing an overview of the standards, conducting surveys addressed to the clinical medical physicists and calibration laboratories and investigating the key comparison database. Results: There are widely available calibration services for air kerma measurements for a large range of radiation qualities. However, there is a lack of calibration services for all other measured quantities, and very few laboratories besides the manufacturers are able to perform these calibrations. In addition, standardization gaps with non-harmonized calibration and measurement procedures for these quantities were found. Conclusion: New calibration services with harmonized procedures are needed for XMMs, especially for quantities beyond air kerma. There is a need to better understand and reduce measurement uncertainty for some quantities. New procedures will be developed within the TraMeXI project and disseminated to the standardization bodies, metrology and medical physics community.