Significance of the sample determination in assessment of radiological examinations frequencies for population doses due to medical exposures.

The radiological examination frequency, i.e. the number of examinations performed annually, is necessary for estimating the collective effective dose of the population from medical exposures with ionizing radiation. Examination frequency surveys usually collect data from a limited number of radiological facilities participating in the survey. The collected data are then extrapolated to the existing radiological facilities in a country/region. Thus, the number of facilities and the specific facilities to participate, as well as, the extrapolation method used, are significant elements when designing the survey sample and methodology for examinations frequency assessments. This work attempted to simulate the situation when examination frequency data are collected from a limited number of facilities by investigating several "virtual sample" designs and two extrapolation methods. Comparisons between the calculated - by extrapolation - and the actual examination frequency in the country were made, for several scenarios and examination type data sets. The uncertainties were estimated and discussed thoroughly. The findings of this work highlighted the need for appropriate registry of the existing facilities in a country/region, the categorization of facilities considering the medical sector pattern in the country/region, the representativity and homogeneity of the samples used for a survey, as well as, the necessity for quality control of the collected examination frequency data. The results showed that when the aforementioned conditions were fulfilled, the examination frequency could be calculated with reasonable accuracy, based on data collected from a limited number of facilities. The paper also provides suggestions and tips for the collection and analysis of examination frequency data.

Updating national diagnostic reference levels for computed tomography in Greece: Challenges on patient protection optimisation.

The escalating use of Computed Tomography (CT) imaging necessitates establishment and periodic revision of Diagnostic Reference Levels (DRLs) to ensure patient protection optimization. This paper presents the outcomes of a national survey conducted from 2019 to 2022, focusing on revising DRLs for adult CT examinations. Dosimetric data from 127 scanners in 120 medical facilities, representing 25% of the country's CT scanners, were collected, emphasizing geographic distribution and technology representation. Τhe parameters used for DRLs were the CTDIvol and the DLP of a typical acquisition of the region of interest (scan DLP). In addition to the 7 CT examination for which the DRL values were revised, establishment of DRLs for neck, cervical spine, pelvic bones-hips, coronary artery calcium (Ca) score and cardiac computed tomography angiography (CCTA) examinations was performed. Revised DRLs exhibited a 15 % average decrease in CTDIvol and a 7 % average decrease in scan DLP from the initial DRLs. This reduction of dosimetric values is relatively low compared to other national studies. The findings revealed wide variations in dosimetric values and scan lengths among scanners, emphasizing the need for standardization and optimization. Incorporation of advanced technologies like Iterative Reconstruction (IR) showcased potential for further dose reduction, yet challenges in uniform implementation persist. The study underscores the importance of ongoing optimisation efforts, particularly in the context of increased CT utilization and evolving technology. The revised DRLs have been officially adopted in Greece, emphasizing the commitment to safe and effective CT practices.

Remote virtual regulatory inspections of facilities and practices utilising ionising radiation and MRI installations during the Covid-19 pandemic.

Covid-19 pandemic imposes crucial social distancing rules and restriction measures; therefore, the access to facilities and sites, in order to perform on-site inspections, became difficult or not feasible. Greek Atomic Energy Commission (EEAE) adopted remote virtual inspections (RVIs) of facilities and practices applying ionising radiation and magnetic resonance imaging installations, in order to continue discharging its regulatory duty of inspection, effectively. This study presents the experience gained and lessons learnt from the implementation of the RVIs and explores the RVIs perception by the stakeholders. Moreover, the effectiveness and the capability of RVIs to identify 'findings', is assessed by comparing the on-site and the remote inspections outcomes. The presented study showed that RVIs could not replace the on-site inspections, entirely; however, they could support and contribute to the inspection activities and program, in certain circumstances. RVIs were proven to be a valuable tool for the inspection of procedures, documents and records as well as the design and operational conditions of the facilities. The performance of remote verification tests and measurements, although feasible, was challenging, due to the technical issues needed to be resolved in advance. The comparison between remote and on-site inspections outcomes showed that both inspection options had similar capability to identify 'findings', indicating the validity of the RVIs as an inspection methodology in certain inspection thematic areas. The perception of the RVIs was positive and the added value and usefulness was acknowledged by the inspected facilities' personnel and the EEAE's inspectors, although the latter mainly considered RVIs as complementary and supportive to the on-site inspections.