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Objectives The objective of this study was to investigate the feasibility of defining diagnostic reference levels (DRLs) on a European basis for specific clinical indications (CIs), within the context of the European Clinical DRLs (EUCLID) European Commission project. Methods A prospective, multicenter, industry-independent European study was performed to provide data on 10 CIs (stroke, chronic sinusitis, cervical spine trauma, pulmonary embolism, coronary calcium scoring, coronary angiography, lung cancer, hepatocellular carcinoma, colic/abdominal pain, and appendicitis) via an online survey that included information on patient clinical, technical, and dosimetric parameters. Data from at least 20 patients per CI were requested from each hospital. To establish DRLs, a methodology in line with the International Commission on Radiological Protection (ICRP) Report 135 good practice recommendations was followed. Results Data were collected from 19 hospitals in 14 European countries on 4299 adult patients and 10 CIs to determine DRLs. DRLs differ considerably between sites for the same CI. Differences were attributed mainly to technical protocol and variable number of phases/scan lengths. Stroke and hepatocellular carcinoma were the CIs with the highest DRLs. Coronary calcium scoring had the lowest DRL value. Comparison with published literature was limited, as there was scarce information on DRLs based on CI. Conclusions This is the first study reporting on feasibility of establishing CT DRLs based on CI using European data. Resulting values will serve as a baseline for comparison with local radiological practice, national authorities when DRLs are set/updated, or as a guideline for local DRL establishment. Key Points • First study reporting on the feasibility of establishing CT diagnostic reference levels based on clinical indication using data collected across Europe. • Only one-fourth of the hospitals had CT machines less than 5 years old. • Large dose variations were observed among hospitals and CT protocols were quite different between hospitals.

Background In August 2017, the European Commission awarded the “European Study on Clinical Diagnostic Reference levels for X-ray Medical Imaging” project to the European Society of Radiology, to provide up-to-date Diagnostic Reference Levels based on clinical indications. The aim of this work was to conduct an extensive literature review by analysing the most recent studies published and the data provided by the National Competent Authorities, to understand the current situation regarding Diagnostic Reference Levels based on clinical indications for computed tomography. Results The literature review has identified 23 papers with Diagnostic Reference Levels based on clinical indications for computed tomography from 15 countries; 12 of them from Europe. A total of 28 clinical indications for 6 anatomical areas (head, cervical spine/neck, chest, abdomen, abdomen-pelvis, chest-abdomen-pelvis) have been identified. Conclusions In all the six anatomical areas for which Diagnostic Reference Levels based on clinical indications were found, a huge variation of computed tomography dose descriptor values was identified, providing evidence for a need to develop strategies to standardise and optimise computed tomography protocols.

Objective To collect and analyze radiation dose metrics from 23 commonly performed CT procedures, for which no national DRLs have yet been defined, as part of an international cooperation. The body region, the clinical task, and the relevant technical parameters were considered to define clinical diagnostic reference levels (DRLs). Materials and methods During 2022–2023, a multicenter study was performed in Austria, Germany, Italy, and Switzerland. Healthcare providers supplied processed data from their dose management systems. The 5%-level was used to assess the statistical significance of dose differences between the countries of participants, as well as age and manufacturer of the scanners. Results Dose metrics from 87 CT systems in academic and non-academic, public and private healthcare facilities were analyzed. Dose values from the same body region but for different clinical tasks and/or using different techniques might differ significantly. For the same procedures, median dose values varied between systems by a factor of up to 39. Approximately a third of the surveyed systems showed doses within the DRLs suggested in this study, while 6% do not fulfill any DRL. No significant dose differences were observed between systems when comparing age, manufacturer or country. Conclusions In this international study, clinical DRLs were suggested for the first time for many different CT procedures, including dose-intensive procedures such as cerebral perfusion or the CT-guided interventional periradicular therapy. The diversity in protocol optimization is one of the main reasons for dose variations. Establishing the proposed DRLs can help harmonize exposure practice across country borders. Critical relevance statement In this international multicenter study, clinical task-based DRLs were suggested for 23 CT procedures to promote the optimization of the exposure practice, to reduce dose variations among institutions, even across national borders and to strengthen international cooperation among users. Key Points Analysis and differences in exposure practices in 23 different CT examinations in four neighboring European countries. Dose values for the same clinical tasks vary considerably between facilities using the same technology, but on average, not between countries. Establishing diagnostic reference levels helps to harmonize the exposure practice across country borders for frequently performed procedures. Graphical Abstract

Objectives To assess information reflecting radiation dose and define diagnostic reference levels (DRL) on a European basis for four interventional radiology (IR) procedures considering clinical indication, anatomical region, and procedure. Methods A prospective European study was performed to provide data on the IR procedures percutaneous recanalization of iliac arteries, percutaneous recanalization of femoropopliteal arteries, transarterial chemoembolization of hepatocellular carcinoma, and percutaneous transhepatic biliary drainage. Hospitals were asked to complete a questionnaire giving information on procedure, equipment, and protocol. Patient size and weight, experience of the operator graded in number of procedures performed, and complexity level of each procedure were reported. Sixteen hospitals from 13 countries could be surveyed. The percentiles of the kerma-area product, fluoroscopy time, cumulative air kerma at the interventional reference point, and number of images were determined. The impact of equipment, year of installation, and complexity level of the procedure on dose were analyzed. Results DRLs based on clinical indication were defined. Dose values varied considerably within hospitals, between them, and within each subgroup of complexity level. The use of state-of-the-art equipment reduced dose significantly by 52%. Although dose also varied within each subgroup of complexity level, for transarterial chemoembolization of hepatocellular carcinoma and percutaneous transhepatic biliary drainage, dose significantly correlated with complexity. Conclusions This was the first study reporting exposure practice and defining DRLs based on clinical indication for four IR procedures on a European basis. These DRLs can serve as a baseline for comparison with local practice, the study as a guideline for future surveys. Key Points • The use of state-of-the-art angiographic equipment reduces dose significantly. • A significant correlation between radiation dose and complexity level is found. • Dose values vary considerably, both within and between individual hospitals, and within each complexity level of interventional radiology procedure.

Purpose To collect and analyze radiation dose-related data as part of international cooperation; to define diagnostic reference levels (DRL) for 24 X-ray projections in plain radiography (DX) considering anatomical region, clinical task, and procedural technique; and to harmonize the exposure practice across country borders. Methods A multicenter study was performed in Austria, Germany, Italy, and Switzerland in 2022–23 to provide dose-related data. Healthcare facilities were asked to provide processed data from their dose management systems. A 5%-level was used for assessing the statistical significance of dose differences between various groups. Results Dose-related data from 85 radiographic systems in academic and non-academic, public, and private healthcare facilities were analyzed. Dose-related parameters differed significantly for many projections with different clinical tasks and techniques. Dose-related data of the procedures varied by a maximum factor of 16 for the same system, and median dose values also differed between hospitals by a maximum factor of 31. A fifth of the surveyed systems exhibit doses above more than half of the new DRLs defined in this study. Apart from the three reference procedures, no significant dose differences were observed between X-ray systems of different ages, from different manufacturers, or from different countries. Conclusions This is the first survey in which exposure practices were investigated in institutions in different central European countries by establishing clinical DRLs for radiography. The observed dose variations could be explained by different reasons, such as non-optimized dose protocols. The new DRLs help to harmonize the exposure practice across country borders. Key Points Question What is the exposure practice for plain radiography procedures for which no clinical diagnostic reference levels (DRLs) have been defined? Are there differences between countries? Findings The dose for the same clinical task and technique can vary considerably among institutions but, on average, do not significantly differ between neighboring countries in Europe. Clinical relevance In this international multicenter study, clinical DRLs were defined for 24 plain radiography projections to promote the optimization of the exposure practice, to reduce dose variations among institutions even across national borders, and to strengthen international cooperation among users.

Introduction Various studies address discrepancies between guideline recommendations for coronary angiographies and clinical practice. While the issue of the appropriateness of recurrent angiographies was studied focusing on the role of the cardiologist, little is known about individual patients’ histories and the associated radiation exposures. Methods We analyzed all patients with coronary artery disease (CAD) in an academic teaching practice who underwent at least one angiography with or without intervention between 2004 and 2009. All performed angiographies in these patients were analyzed and rated by three physicians for appropriateness levels according to cardiology guidelines. Typical exposure data from the medical literature were used to estimate individual radiation exposure. Results In the cohort of 147 patients, a total of 441 procedures were analyzed: between 1981 and 2009, three procedures were performed per patient (range 1–19) on average. Appropriateness ratings were ‘high/intermediate’ in 71 %, ‘low/no’ in 27.6 % and data were insufficient for ratings in 1.4 %. Procedures with ‘low/no’ ratings were associated with potentially avoidable exposures of up to 186 mSv for single patients. Conclusions Using retrospective data, we exemplify the potential benefit of guideline adherence to decrease patients’ radiation exposures. Key Points • A cohort study of 147 patients showed 27.6 % low appropriateness procedures . • Potentially avoidable radiation exposure cumulated up to about 186 mSv for single patients . • Predisposing factors were prior bypass surgery and first treatment in a tertiary centre. • 7.5 % of the patients received 58 % of the potentially avoidable radiation exposure . • The benefits of guideline adherence in decreasing patient radiation exposure are exemplified .

HintergrundIn Deutschland resultieren etwa 95 % der zivilisatorischen Strahlenexposition der Bevölkerung aus diagnostischen und interventionellen Röntgenanwendungen, sodass dem Strahlenschutz der Patienten in diesem Anwendungsbereich eine hohe Bedeutung zukommt.Ziel der ArbeitAuswertung und Bewertung aktueller Daten zu Häufigkeit und Dosis von Röntgenanwendungen sowie von zeitlichen Entwicklungen für die Jahre 2007 bis 2014.Material und MethodenDie Häufigkeit von Röntgenanwendungen wurde für den ambulanten Bereich über Gebührenziffern der erbrachten radiologischen Leistungen abgeschätzt, für den stationären Bereich mithilfe von Krankenhausstatistiken. Repräsentative Werte für die effektive Dosis pro Röntgenanwendung wurden für die betrachteten Jahre überwiegend aus Daten der Ärztlichen Stellen ermittelt.ErgebnisseIm Jahr 2014 wurden in Deutschland etwa 140 Mio. Röntgenanwendungen durchgeführt, hiervon etwa 40 % im zahnmedizinischen Bereich. Im Mittel erfolgten 2007–2014 nahezu konstant 1,7 Anwendungen pro Einwohner und Jahr. Neben der zahnmedizinischen Diagnostik wurden am häufigsten konventionelle Untersuchungen des Skeletts und des Thorax durchgeführt. Die CT-Häufigkeit nahm um ca. 40 % zu. Mit etwa 55 % war der Anstieg bei der MRT zwar noch deutlicher, jedoch wurden insgesamt noch immer mehr CT- als MRT-Untersuchungen durchgeführt. Die Dosiswerte pro Untersuchung nahmen trotz der in den letzten Jahren etablierten Methoden zur Dosisreduktion nur leicht ab. In der Konsequenz nahm die mittlere effektive Dosis pro Einwohner im Untersuchungszeitraum von knapp 1,4 auf 1,6 mSv zu – im Wesentlichen aufgrund der zunehmenden CT-Häufigkeit.SchlussfolgerungDie Prinzipien der Rechtfertigung und Optimierung von medizinischen Strahlenanwendungen sind – insbesondere bei CT-Untersuchungen – in jedem Einzelfall konsequent anzuwenden.

We investigate the structure of the innermost region of three circumstellar disks around pre-main sequence stars HD 142666, AS 205 N, and AS 205 S. We determine the inner radii of the dust disks and, in particular, search for transition objects where dust has been depleted and inner disk gaps have formed at radii of a few tenths of AU up to several AU. We performed interferometric observations with IOTA, AMBER, and MIDI in the infrared wavelength ranges 1.6-2.5um and 8-13um with projected baseline lengths between 25m and 102m. The data analysis was based on radiative transfer simulations in 3D models of young stellar objects (YSOs) to reproduce the spectral energy distribution and the interferometric visibilities simultaneously. Accretion effects and disk gaps could be considered in the modeling approach. Results from previous studies restricted the parameter space. The objects of this study were spatially resolved in the infrared wavelength range using the interferometers. Based on these observations, a disk gap could be found for the source HD 142666 that classifies it as transition object. There is a disk hole up to a radius of R_in=0.30AU and a (dust-free) ring between 0.35AU and 0.80AU in the disk of HD 142666. The classification of AS 205 as a system of classical T Tauri stars could be confirmed using the canonical model approach, i. e., there are no hints of disk gaps in our observations.

Context: It is hypothesized that low-mass young stellar objects undergo eruptive phases during their early evolution. The outburst of V1647 Ori between 2003 and 2006 offered a rare opportunity to investigate such an accretion event. Aims: By means of our interferometry observing campaign during this outburst, supplemented by other observations, we investigate the temporal evolution of the inner circumstellar structure of V1647 Ori We also study the role of the changing extinction in the brightening of the object and separate it from the accretional brightening. Methods: We observed V1647 Ori with MIDI/VLTI at two epochs in this outburst. First, during the slowly fading plateau phase (2005 March) and second, just before the rapid fading of the object (2005 September), which ended the outburst. We used the radiative transfer code MC3D to fit the interferometry data and the spectral energy distributions from five different epochs at different stages of the outburst. The comparison of these models allowed us to trace structural changes in the system on AU-scales. We also considered qualitative alternatives for the interpretation of our data. Results: We found that the disk and the envelope are similar to those of non-eruptive young stars and that the accretion rate varied during the outburst. We also found evidence for the increase of the inner radii of the circumstellar disk and envelope at the beginning of the outburst. Furthermore, the change of the interferometric visibilities indicates structural changes in the circumstellar material. We test a few scenarios to interpret these data. We also speculate that the changes are caused by the fading of the central source, which is not immediately followed by the fading of the outer regions. However, if the delay in the fading of the disk is responsible for the changes seen in the MIDI data, the effect should be confirmed by dynamical modeling.