Addressing gaps in calibration and standardization of X-ray measurement systems for medical use

The medical use of X-rays represents the largest source of artificial ionizing radiation exposure to the global population. To ensure optimal performance and safety in imaging and interventional procedures, quality control is commonly performed by measuring key parameters of the X-ray system, such as air kerma, tube voltage, and half-value layer layer non-invasively from X-ray beam using X-ray multimeters (XMMs). While some parameters benefit from established standardization and metrological support, others still lack a unified and consistent approach. Moreover, there is a shortage of data on the performance of XMMs in varying measurement conditions. A study was performed to assesses the existing standards and identify calibration and measurement needs by reviewing available guidelines, conducting surveys with clinical medical physicists and calibration laboratories, and analyzing data from the key comparison database. Calibration services for air kerma are readily available across a broad range of radiation qualities. However, calibration services for other key parameters are scarce, with very few laboratories—primarily manufacturers— able to provide these services. Additionally, gaps in standardization exist, and calibration procedures for these quantities lack harmonization. The surveys also showed that different countries have different requirements for calibration, verification and type testing of XMMs, and that the use of calibration coefficients by medical physicists is very sporadic. To address these issues, the development of new calibration services with harmonized procedures for X-ray multimeters is essential, particularly for parameters beyond air kerma. These procedures will be formulated within the framework of the TraMeXI project and subsequently shared with standardization bodies, metrology organizations, and the medical physics community. The project also develops procedures for clinical measurements, including the recommendations on the use of calibration coefficients and standardized measurement setups.