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Fluoroscopically guided procedures might be highly irradiating for patients, possibly leading to skin injuries. In such a context, every effort should be done to lower patient exposure as much as possible. Moreover, patient dose reduction does not only benefit to the patient but also allows reducing staff exposure. In this framework, Philips Healthcare recently introduced a system upgrade for their angiography units, called 'AlluraClarity'. The authors performed air kerma rate measurements for all available fluoroscopy modes and air kerma per frame measurements for the digital subtraction angiography protocols, along with subjective spatial resolution and low-contrast detectability assessments using a standard QA phantom. Air kerma reductions ranging from 25.5 to 84.4 % were found, with no significant change in image quality when switching from a standard operating mode to an upgraded version. These results are confirmed by the comparison of actual patient exposures for similar procedures.

Since January 2008-de facto 2012-medical physics experts (MPEs) are, by law, to be involved in the optimisation process of radiological diagnostic procedures in Switzerland. Computed tomography, fluoroscopy and nuclear medicine imaging units have been assessed for patient exposure and image quality. Large spreads in clinical practice have been observed. For example, the number of scans per abdominal CT examination went from 1 to 9. Fluoroscopy units showed, for the same device settings, dose rate variations up to a factor of 3 to 7. Quantitative image quality for positron emission tomography (PET)/CT examinations varied significantly depending on the local image reconstruction algorithms. Future work will be focused on promoting team cooperation between MPEs, radiologists and radiographers and on implementing task-oriented objective image quality indicators.

Diagnostic reference levels (DRLs) were established for 21 indication-based CT examinations for adults in Switzerland. One hundred and seventy-nine of 225 computed tomography (CT) scanners operated in hospitals and private radiology institutes were audited on-site and patient doses were collected. For each CT scanner, a correction factor was calculated expressing the deviation of the measured weighted computed tomography dose index (CTDI) to the nominal weighted CTDI as displayed on the workstation. Patient doses were corrected by this factor providing a realistic basis for establishing national DRLs. Results showed large variations in doses between different radiology departments in Switzerland, especially for examinations of the petrous bone, pelvis, lower limbs and heart. This indicates that the concept of DRLs has not yet been correctly applied for CT examinations in clinical routine. A close collaboration of all stakeholders is mandatory to assure an effective radiation protection of patients. On-site audits will be intensified to further establish the concept of DRLs in Switzerland.

The purpose of this work was to compare standard desktop display systems with dedicated medical display systems. The set of image tests proposed by the American Association of Physicists in Medicine (AAPM TG18) was used to assess a Philips 107S desktop display system and a Siemens medical display. Three observers performed the subjective assessment, in a non-concerted manner. The objective assessment was performed using a CCD camera according to the AAPM TG18 procedure. The results clearly demonstrate the inadequacy of standard desktop display systems in the framework of diagnostic radiology. Moreover, a good correlation between the subjective and objective assessment methods was obtained.

The RADIUS (Radiological Imaging Unification Strategy) project addresses the assessment of image quality in terms of both physical and clinically relevant measures. The aim is to unify our understanding of both types of measure as well as the numerous underlying factors that play a key role in the assessments of imaging performance. In this way it is expected to provide a solid basis for the improvement in radiological safety management, where not only radiation risks are considered but also diagnostic risks of incorrect clinical outcomes (i.e. false positive/false negative). The project has applied a variety of relevant experimental and theoretical methods to this problem, which is generic to medical imaging as a whole. Digital radiography of the chest and the breast has been employed as the clinical imaging domain vehicles for the study. The project addressed the problem from the following directions: role and relevance of pathology, human observer studies including receiver operating characteristics, image quality criteria analysis, structural noise analysis, physical measurements on clinical images, physical measurements on imaging system, modelling of imaging system, modelling of visual processes, modelling of doses delivered and IT-based scientific support strategies. This paper presents an overview of the main outcomes from this project and highlights how the research outcomes actually apply to the real world. In particular, attention will be focused on new and original findings and methods and techniques that have been developed within the framework of the project. The relevance of the project's outcomes to future European research will also be presented.

The aim of this paper is to compare the image quality of different CT units at four centres using first the same dose per slice, and then the dose per slice used when performing a standard abdominal acquisition. The results show that the detection of a 7 to 9 mm supra-slice object (i.e. larger than the slice thickness) of 0.5% can be obtained at a comparable dose level. The main difference between the performances of the CT appears when trying to detect a contrast level of 0.3%. When comparing the CT using the clinical acquisition parameters chosen, the same conclusions can be drawn in spite of the fact that the CTDI values varied by 65%. The most important result is the comparison of the effective dose which shows differences up to almost 100% between the centres involved. This paper confirms that the DLP concept is a powerful tool for the optimisation of CT examination protocols.

A Monte Carlo computer program has been developed to model X ray imaging systems realistically using an adult voxel phantom. Image quality is quantified in terms of contrast and signal-to-noise ratio (SNR) for six important anatomical details chosen in accordance with recent European guidelines. The program has been used to study and optimise lumbar spine (LS) radiographic systems. As an example, the effect of tube potential on contrast, SNR and effective dose for the LS AP examination is demonstrated. Optimisation involves comparison of performance with that of a reference system. Configurations (tube potential, grid and screen-film) have been found which approximately match the reference image quality, but at lower effective dose. Various configurations give good performance. Some result in significant dose reduction. For LS AP 400 and 600 speed-class systems, dose savings of 21% and 34% are achievable. The model is thus a powerful tool for system optimisation.

Characterisation of film digitisers should be the first step when using them in the medical field: unfortunately, there is still no standard protocol to do so. This situation is particularly critical because the use of film digitisers is becoming a routine procedure in centres willing to set up PACS systems. The assessment of basic parameters such as the range and resolution of optical density, the spatial resolution and the noise level can be easily implemented and allows a check on the level of image degradation produced by film digitising. Simple methods are reported which could be included in quality assurance programmes of hospitals or centres using these systems.

A subjective and an objective comparison of six screen-film systems is reported. Among the objective parameters which characterise image quality, resolution appeared to he the most critical one when compared with the averaged ranking produced by the radiologists. The results have shown that a relationship between dose and image quality can be established for most of screen-film systems tested. The problem which remain s in the optimisation procedure of chest imaging, is the definition of the level of image quality requirements.

The definition of reference dose levels has to be linked with the definition of image quality. Unfortunately, there is still no general agreement on the definition of image quality in mammography, and most of the protocols used are based on the detectability of objects having various shapes and contrasts. To facilitate the task of assessing image quality, scoring methods are often used to produce a single number representative of the imaging chain performance. The goal of this study is to present a comparison between different ways of assessing image quality commonly used in Europe. A set of five mammograms, having different image quality levels, has been obtained with several test objects and compared. The results show large sensitivity variations among the different methods. Concerted work between radiologists and physicists is still required to define the radiological tasks and develop objective ways to measure image quality in mammography.

The results are reported of a survey which consisted of recording the entrance surface dose of the most common examinations performed in our hospital. For two examinations dose-area products have also been recorded in order to demonstrate that the entrance surface dose and dose-area product were independent pieces of information in fluoroscopy An analysis of the ways to optimise the examinations is also discussed.