Background: Dosimeter type-testing and verification, in addition to regular calibration, ensures the acquisition of high quality dosimetry data and optimization of radiation protection. Aim: Historical and aggregated calibration data of active dosimeters for individual and area workplace monitoring from several Standard Dosimetry Calibration Laboratories was collected and evaluated in terms of variation in response due to radiation-based influence quantities. These data can be used to support future update and harmonization of type testing standards. Methods: Dosimeter performance was examined in a wide range of dose rates, covering several orders of magnitude within the measurement ranges, and from 33.3 keV to 1.25 MeV photon energies, respectively. The results were evaluated against limits of variation defined in type testing standards IEC 61526:2024 and IEC 60846-1:2009 for active personal and active ambient dosimeters, respectively. Results: Most commonly used dosimeters complied with the standard requirements, with some state-of-the-art models exhibiting excellent performance and small response variations within standard stated limits, even beyond the minimum rated ranges. However, some units had pronounced variation in response, up to +68 % for active personal dosimeters and +75 % for active ambient dosimeters. Additionally, devices with inappropriate energy compensation were identified, having an over-response up to +650 %. Conclusion: These findings confirm the importance of type testing of dosimeter models, along with verification and regular calibration of individual units. Performance indicators showcase that most dosimeters comply with the standards, while some behaved far better, allowing for possibility of proposing a category of radiation protection field instruments with lower uncertainties.

INTRODUCTION:Mammography measurements are commonly conducted in a radiation field of standard size without additional collimation of the primary beam. International standards, protocols and guidelines propose half-value layer (HVL) measurements under narrow beam conditions, which are not applied in clinical measurements. METHODS:The HVL was measured using an ionization chamber and X-ray multimeters (XMMs) in different field collimations in radiation qualities commonly encountered in mammography. The impact of field size on measured HVL was examined for Mo/Mo, Mo/Rh, W/Rh and W/Ag anode/filter combinations, for X-ray tube voltages of 25 kV, 28 kV, 30 kV and 35 kV. RESULTS:Field size has a significant influence on the HVL measured with the ionization chamber. Up to 5 % differences were observed and it was impacted by irradiation geometry (field shape and usage of compression paddle) and radiation quality. The XMMs do not have similar behaviour. CONCLUSION:With ionization chambers, the HVL should be measured following the definition in a narrow beam without scatter. The XMMs are not so sensitive to scattered radiation but they should have a traceable calibration in terms of HVL for specific radiation qualities in use.

X-ray multimeters (XMMs) are widely used for quality control measurements in mammography, providing air kerma, half-value layer (HVL), and tube voltage from a single exposure. The energy dependence of their response was comprehensively investigated for various anode/filter combinations and software selections. However, the influence of a change in the X-ray spectrum due to additional material in the beam has not yet been systematically investigated. The aim of this study is to quantify the sensitivity of XMM calibration coefficients to changes in X-ray spectra introduced by additional polymethyl methacrylate (PMMA) of different thicknesses. Four commercially available XMMs were calibrated at the IAEA dosimetry laboratory for air kerma, HVL, and tube voltage using two anode/filter combinations (Mo/Mo and W/Al) at tube voltages ranging from 25kV to 35kV. Calibration coefficients were determined without additional filtration and with PMMA thicknesses of 2.0mm, 2.8mm, and 4.8mm placed close to the X-ray tube to modify the primary spectrum while minimizing scattered radiation reaching the detectors. In relation to the calibration coefficient determined without PMMA deviations of up to 11% were observed for air kerma rate. HVL and tube voltage calibration coefficients exhibited substantially larger deviations, reaching up to 37% and 42%, respectively. We conclude that changes in the X-ray spectra as from additional PMMA filtration, can substantially alter XMM calibration coefficients, particularly for HVL and tube voltage measurements. XMM responses are highly sensitive to spectral modifications beyond standard anode/filter combinations and tube voltage settings.

The ISO 4037:2019 standard is the reference standard for dosimetry laboratories who wish to realize dosimetric operational quantities for radiation protection calibrations. In implementing the ISO 4037:2019 standard, the X-ray radiation qualities need to be defined according to strict requirements on the material and thickness of the additional filtration, and according to metrologically traceable high voltage bias applied to the X-ray tube. This enables usage of standardized conversion coefficient from air kerma to operational quantities. However, the tube potential may vary as a function of tube current if a protective resistor is built into the protective tube housing, which, if not corrected, alters the energy distributions of the reference field and thus the value of the appropriate conversion coefficients. Particularly at low energies, the energy dependence of the conversion coefficients can be sharp and, depending on the specific realization of a radiation quality, the conversion coefficient from air kerma to dose equivalent can vary substantially. We have investigated the correspondence between the tube voltage measurements of a X-ray system based on calibrated voltage dividers and that of an X-ray spectrometer system based on a Cadmium Telluride (CdTe) detector in order to obtain an estimation of the resistance of the protective resistor that is usually unknown. A method based on X-ray spectrometry for calibration of the tube potential even in the presence of tube with protective resistor is presented. Finally, conversion coefficients were calculated using simulated spectra to study the influence of the protective resistor on the determination of these coefficients. The simulated spectra obtained from X-ray tube with and without a protective resistor resulted in differences in conversion coefficients mostly ˂2% but 5.6% for the radiation quality considered at the lowest energy.

Introduction X-ray medical imaging developments have introduced needs for updated dosimetry practices. Methods Performance of commercially available dosimeters used for air kerma measurements in diagnostic and interventional radiology was examined. Ionization chambers and X-ray multimeters were tested in a wide range of air kerma rates, photon energies (using standard and non-standard radiation qualities), and angles of incidence with different dosimeter orientation and rotation. Stability and repeatability of the measured value, the influence of pulse duration, non-linearity of dosimeter response, energy and angular dependence were studied against the IEC 61674:2024 limits of variation. Energy response was tested using the standard RQR and RQT radiation qualities defined in IEC 61267:2005, as well as non-standard copper-filtered beams with added 0.9 mm Cu filtration. Results Most dosimeters complied with the IEC 61674:2024 standard limits of variation, for both standard and non-standard radiation fields. In some cases, observed performance was significantly better than the current limits allowing for the introduction of more stringent values. Conclusion Modification of the performance requirements was proposed, considering differences between reference-class and field-class dosimeters, while introducing more stringent requirements for reference-class dosimeters.

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.

Ensuring comprehensive quality control of breast imaging systems involving ionizing radiation like mammography and tomosynthesis is crucial for high diagnostic confidence and maintaining an acceptable patient dose. This requires accurate dosimetric measurements, including air kerma, half-value layer (HVL), and tube voltage as key quantities. Ionization chambers or semiconductor-based X-ray multimeters (XMMs) are used to measure these parameters, with XMMs also displaying tube voltage in one exposure in addition to numerous other parameters. To correct for the influence of slight changes in the X-ray spectra on the response of XMMs, dedicated algorithms are implemented in the XMMs’ software. They often require manual selection of anode/filter combinations prior the measurements. However, to ensure comparability, consistency, and traceability, measurement equipment must be calibrated for each specific measurement quantity. National dosimetry laboratories may have limited options for calibration, and errors can occur if the wrong combination is selected in the XMM software. This study investigates the hypothesis that the selection of the anode/filter combination in XMM software influences the readings. The primary objective is to evaluate the impact of different anode/filter combinations selected in the software on the measurement of air kerma, half-value layer (HVL), and tube voltage. Additionally, the study assesses the feasibility of performing quality assurance for XMMs using a limited range of anode/filter combinations. The readings of eight commercially available XMMs for air kerma rate, HVL and tube voltage were compared with the reference values realized in the IAEA secondary standards dosimetry laboratory for five anode/filter combinations and tube voltages ranging from 25 to 35 kV. The deviation of XMMs readings with different selections of anode/filter combinations in the software was studied. The maximum deviation when anode/filter combination selected in the XMM software matched the anode/filter combination of the X-ray beam was 19% for air kerma, 9% for tube voltage and 10% for HVL. When the selected anode/filter combination set differed from the one used, maximum deviation increased up to 31% for air kerma, 44% for tube voltage and 45% for HVL. Appropriate selection of the anode/filter combination in the XMM software is crucial for obtaining reliable measurement results. Interpolation of calibration coefficients between different radiation qualities and selections is not recommended.

Quality control and assurance of mammography X-ray generators include usage of solid-state detectors and/or ionization chambers which are calibrated in standard reference radiation fields. IEC 61267:2005 standard defines reference mammography radiation fields for Mo/Mo anode/filtration, while various anode/filtration combinations are encountered in clinical mammography X-ray units. Not all Secondary Standard Dosimetry Laboratories have an X-ray generator with Mo/Mo radiation setup, thus traceability can be established only for the available anode/filter combinations which is commonly limited to W/Al. In this study, W/Al radiation fields were established under laboratory conditions by performing half-value layer measurements, and characterization of four solid-state detectors was performed. X-ray multimeter performance was evaluated in terms of energy response in the W/Al radiation fields. In the laboratory conditions the energy response of the dosimeters had larger deviation from unity for dosimeters without appropriate anode/filter combination selected in the software settings, even though most of the dosimeters had uniform relative response. Discrepancy in the response was further investigated by examining its variation induced by available detector software settings, and it was determined that the dosimeter response can vary up to 20 %. In clinical setup, half-value layer was determined, and detector performance was examined. Dosimeters were tested in clinical fields with Mo/Mo, Mo/Rh, W/Rh, W/Ag anode/filter combinations in the X-ray tube voltage range from 25 kV to 35 kV. For most clinical radiation fields, multi-element detectors had energy response deviation within ±5 %. The single-element detector had one software setting available and has exhibited strong energy dependence. Extensive testing of detector response such as presented in this paper allows for correction factor interpolation based on half-value layer.

The effect of mammography measurement conditions was investigated to evaluate their impact on measurement uncertainties in clinical practice. The most prominent physical X-ray beam quantities i.e., - air kerma, half-value layer, and X-ray tube voltage - were examined by measuring the response of two ionization chambers and six Xray multimeters (XMMs) of different models. Measurements were performed using several anode/filter combinations and both with and without the compression paddle in the X-ray beam. Maximum differences of higher than 6 % were found for all quantities when the dosimeter displayed value was compared with the reference value or the variation within the clinical anode/filter combinations Mo/Mo and Mo/Rh were considered. The study showed that the calibration procedure with the W/Al anode/filter combination was reliable only for ionization chambers, and the response of XMMs varies in such a way that the calibration coefficient cannot be predicted between various measurement conditions used in calibration and clinical practices. XMM calibrations are typically performed without a compression paddle in the beam, and the response of the XMM changes when radiation quality is slightly altered. If XMM specific data is not available, based on this study, an additional uncertainty of 2 % (k = 1) could be used as a typical estimate, at least for air kerma measurements. XMMs should be used for clinical measurements in mammography only with correct settings. If the correct settings are not available, the XMMs should not be used or used only with extreme caution.

Purpose This presentation shares highlights of the International Atomic Energy Agency (IAEA) Technical Report Series 492 Code of Practice on brachytherapy (BT) dosimetry. Methods This IAEA Code of Practice is addressed to both secondary standards dosimetry laboratories (SSDLs) and hospitals, not addressed to primary standards dosimetry laboratories (PSDLs), and is based on the use of well-type re-entrant ionization chambers. It applies to all BT sources with intensities measurable by such detectors. The dosimetry formalism, common procedures for reference dosimetry and for calibration, reference-class instrument assessment, and commissioning of well-type chamber system are described. This Code of Practice is aimed to enable common procedures to perform dosimetry of radioactive sources used in BT, excluding beta-emitting eye plaques/applicators as well as stranded seeds and mesh-type sources. Targeted radionuclide therapy and miniature electronic brachytherapy (eBT) devices were also excluded. It provides a description of the most accurate and sensitive calibration systems available at PSDLs and recommends suitable detectors and procedures for source strength measurements at SSDLs and hospitals. Results This Code of Practice consists of ten sections and six appendices. Following the introduction in Section 1 that frames the background and scope, Section 2 provides a description of the radioactive sources currently available for BT. The dosimetric quantities reference air kerma rate, air kerma strength and absorbed dose to water are discussed in Section 3, along with the dose-rate constant and other parameters important to dosimetrically characterize BT sources. Section 4 provides a detailed description of well-type ionization chamber instrumentation and defines the requisites for reference-class instruments. It also includes a description of HDR remote afterloaders. Section 5 contextualizes the dosimetry framework that defines dissemination of primary dosimetry standards down to the hospital level. Section 6 provides an overview of the available primary standards useful for BT calibrations. Their dissemination through the adoption of a well-type chamber dosimetry system is furthermore described. Section 7 defines the dosimetry formalism employed for the determination of the dosimetry quantities used herein. The general procedure to properly perform BT dosimetry with the well-type chamber is given in Section 8, along with a description of methods to check for short and long term stability of the measurement system. Section 9 deals with estimating uncertainties typically involved with source strength measurement of LDR and HDR sources. The way measured reference quantities are useful in the clinical practice for assessing the dose to the patient is outlined in Section 10. The main BT source categories and treatment delivery methods are briefly approached. Appendices are provided to complement the information given in the main body of the publication: Appendix I briefly mentions antiquated quantities and units that are not recommended to be used any more for dosimetry purposes; Appendix II provides insight into the present situation for dosimetry standards based on air kerma and absorbed dose to water; Appendix III provides a brief description of eBT devices and the current status of their dosimetry standards; Appendix IV provides insight into some detector systems different from the well-type ionization chamber that might be used for BT dosimetry; Appendix V describes the formalism found in the AAPM Task Group 43 Report, which is commonly used for dose distribution calculation in interstitial and intracavitary BT; Appendix VI introduces the theory for estimating measurement uncertainties. Conclusions Guidance and recommendations for BT dosimetry in relation to identified good practices are presented for international harmonization.

Advanced imaging techniques play a pivotal role in oncology. A large variety of computed tomography (CT) scanners, scan protocols, and acquisition techniques have led to a wide range in image quality and radiation exposure. This study aims at implementing verifiable oncological imaging by quality assurance and optimization (i-Violin) through harmonizing image quality and radiation dose across Europe. The 2‑year multicenter implementation study outlined here will focus on CT imaging of lung, stomach, and colorectal cancer and include imaging for four radiological indications: diagnosis, radiation therapy planning, staging, and follow-up. Therefore, 480 anonymized CT data sets of patients will be collected by the associated university hospitals and uploaded to a repository. Radiologists will determine key abdominopelvic structures for image quality assessment by consensus and subsequently adapt a previously developed lung CT tool for the objective evaluation of image quality. The quality metrics will be evaluated for their correlation with perceived image quality and the standardized optimization strategy will be disseminated across Europe. The results of the outlined study will be used to obtain European reference data, to build teaching programs for the developed tools, and to create a culture of optimization in oncological CT imaging. The study protocol and rationale for i‑Violin, a European approach for standardization and harmonization of image quality and optimization of CT procedures in oncological imaging, is presented. Future results will be disseminated across all EU member states, and i‑Violin is thus expected to have a sustained impact on CT imaging for cancer patients across Europe.

Cone beam computed tomography (CBCT) may provide essential additional image guidance to endovascular abdominal aneurysm repair (EVAR) operations but also significant radiation exposure to patients if scans are not carefully optimized. The purpose of our study was to define the image quality requirements for intraoperative EVAR CBCT imaging and to optimize the CBCT exposure parameters accordingly. A Multi-Energy CT phantom simulating a large patient was used by replacing the central phantom cylinder with a custom water-filled insert including an EVAR stent. Different exposure parameters covering a range of radiation qualities and dose levels were used to define the optimal image quality level regarding stent graft evaluation (compressed, bent, or collapsed). The radiation dose was measured with a calibrated air kerma-area product (KAP) meter and organ doses were calculated based on Monte Carlo simulations and a mathematical patient model. Based on the results, updated exposure parameters with the highest mean energy and lowest dose level available were recommended. With the updated protocol, the radiation exposure could be significantly decreased. The KAP value decreased from 9720 mu Gy center dot m(2) to 440 mu Gy center dot m(2) and reference point air kerma from 351 mGy to 16 mGy (a reduction of 96%) and organ doses of the organs in the irradiated region decreased on an average 91%. The new protocol resulted in acceptable clinical image quality based on testing with clinical cases.

Main text The results of the COOMET supplementary comparison of the national measurement standards of air kerma for x-radiation qualities used for radiation protection and diagnostic radiology are presented. Nine National Metrology Institutes from the COOMET organization and the International Atomic Energy Agency participated in this COOMET project no.641. The BelGIM acted as a pilot laboratory. The comparison reference value (CRV) was obtained as the mean result of the PTB and the VNIIM. Almost all participants obtained valid results which were consistent within the relative standard uncertainties of the comparison ranging from 0.28% to 2.6%. Some participants had unacceptable results. To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).