The Swedish field of digital X-ray imaging has since several years relied heavily on distributed information systems and digital storage containers. To ensure accurate and safe radiological reporting, Swedish software-firm eCare AB delivers a system called Feedback—the first and only quality assurance IT support product of its kind. This thesis covers several aspects of the design and implementation of future versions of this software platform. The focus lies on distributed directory services and models for secure and robust data propagation in TCP/IP networks. For data propagation, a new application, InfoBroker, has been designed and implemented to facilitate integration between Feedback and other medical IT support systems. The directory services, introduced in this thesis as the Feedback Directory Services, have been designed on the architectural level. A combination of CORBA and Java Enterprise Edition is suggested as the implementation platform.

L'imagerie par rayons X est fortement développée dans notre société et notamment dans les domaines industriels, médicaux ou sécuritaires. L'utilisation de cette méthode d'imagerie des structures internes (pour la détection d'irrégularité, de contrôle non destructif de pièces ou de menaces) est quotidienne. En radiographie, le contraste produit sur les images est relié à la variation de l'atténuation du flux de rayons X, qui est fonction de la densité, de l'épaisseur du matériau étudié ainsi que de la longueur d'onde utilisée. Ainsi par exemple, des gaines métalliques, des os ou des armes amènent du contraste sur l'image. Mais en plus de leur atténuation, les rayons X vont subir un déphasage qui est d'autant plus important que le matériau est peu atténuant. Ce phénomène va amener du contraste, dit de phase, permettant d'imager des matériaux peu denses tels que des plastiques, composites, tissus mous ou explosifs. Ce travail de thèse présente le développement et l'adaptation, dans le domaine des rayons X, de méthodes d'imagerie par contraste de phase sur des équipements de laboratoire. Le but est de compléter, d'une manière plus accessible et quotidienne, les demandes d'évaluation non destructives. Ce manuscrit se découpe suivant deux axes portant sur la simulation d'une part et sur le développement instrumental d'autre part. Un outil de simulation a été développé portant sur une description hybride alliant optique géométrique et optique ondulatoire. Les limites du modèle et des validations sont présentées. La partie instrumentale se focalise sur l'étude de deux techniques d'imagerie différentielle de phase. La première technique est de l'interférométrie à décalage multilatéral, dont l'adaptation sur tube à rayons X est réalisée pour la première fois. Une exploitation intéressante de la redondance de la mesure que produit la technique sera notamment introduite. La deuxième approche est une technique d'interférométrie de suivi de tavelure, dont nous présenterons une nouvelle exploitation. / X-ray imaging is widely used in non-destructive testing dedicated to industry, medical or security domain. In most of the radiographic techniques, the image contrast depends on the attenuation of the X-ray beam by the sample. This attenuation is function of the density and thickness of the object and of the wavelength. Therefore, objects like metal covers, bones or weapons bring contrast on the image. In addition to attenuation, phase shifting happens, in particular for low-attenuating material. This phenomenon brings contrast, called phase contrast, and allows a X-ray image of low-attenuating material as plastics, composites, soft tissues or explosives. This work presents development and adaptation, in the X-ray domain, of phase contrast imaging techniques on laboratory equipment. The goal is to bring phase contrast imaging in daily use. This manuscript is split in two parts, simulation and instrumentation. A simulation tool has been developed, mixing geometrical optic and wave optic. Limits of the model and validation are presented. For the instrumental part, two interferometric techniques have been considered. The first one is multi-lateral interferometry where adaptation on X-ray tube is presented for the first time. Interesting use of the measurement recurrence will be introduced. The second one is speckle tracking interferometry, recently adapted on X-ray tube, for which we present new advancements.

In this thesis, we present ProxiSART, a flexible proximal framework for robust 3D cone beam tomographic reconstruction based on the Simultaneous Algebraic Reconstruction Technique (SART). We derive the proximal operator for the SART algorithm and use it for minimizing the data term in a proximal algorithm. We show the flexibility of the framework by plugging in different powerful regularizers, and show its robustness in achieving better reconstruction results in the presence of noise and using fewer projections. We compare our framework to state-of-the-art methods and existing popular software tomography reconstruction packages, on both synthetic and real datasets, and show superior reconstruction quality, especially from noisy data and a small number of projections.

Continuous improvement of image quality is one of the priorities in medical imaging. Therefore, development of a simulation tool allowing to generate realistic images would be of great value to understand better the impact of the components on the image quality metrics and to choose imaging set-ups or new design features to optimize output of existing systems and to prototype new ones and to formalize the link between objective and subjective image quality metrics. Therefore, the purpose of this project, was to contribute to adaptation and validation of an existing simulator for simulation of C-arm X-ray imaging. Firstly, the study of the existing simulation tool was performed to choose further development axes. Afterwards, preliminary estimations of simulation complexity by evaluating the number of photons for a given imaging examination were performed. Previous studies[1] showed the determining impact of focal spot on imaging performance (reducing the limiting spatial frequency in common examination conditions) of X-ray interventional imaging systems.  Therefore, the work focused on the improvements of source model, in particular realistic focal spot was defined and simulations of images with close-to-real sharpness were performed and compared to experimentally acquired images. Finally, a part of this project was dedicated to scatter study. An experimental set-up and "scatter map" analysis were designed to determine the scatter evolution as function of imaging field-of-view.  First simulations were also performed. [1] Samei, E., Ranger, N., MacKenzie, A., Honey, I., Dobbins, J. and Ravin, C. (2008). Detector or System? Extending the Concept of Detective Quantum Efficiency to Characterize the Performance of Digital Radiographic Imaging Systems 1. Radiology, 249(3), pp.926-937.

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The author discusses the difficulties that arise with the determination of the concentration of the iodinated contrast agents in the blood stream via the traditional gray-scale computer tomography and searches for the new imaging modalities that would provide for better sensitivity. The topic of the energy-discriminative color CT is discussed as a potential solution and its suitability is evaluated by performing the experiments on the contrast materials phantom and the phantom containing the iohexol solutions of varying concentrations on the original CT system assembled by the author. A method of the effective atomic number mapping is discussed as a viable alternative to the traditional attenuation-based tomography. The dependency of the effective atomic number of the compound on the energy of the x-ray beam is a phenomenon well recorded in the literature, yet no formal study exists to correctly predict the effective atomic number for a given compound. An extensive physical model is developed based on the previously presented models and adaptations unique to the task in order to determine the effective atomic numbers for exact energies experimentally. The method is tested on different materials. The resultant effective atomic numbers for the water, oil, and iohexol-water solutions of varying concentrations are presented in the study. The effects of the k-edge on both the linear attenuation curve and the effective atomic number curve are discussed. The possible future venues of the research are presented in the final part of the thesis. / Master of Science

Yes / This study aimed to determine whether a reduction in radiation dose was found for percutaneous coronary interventional (PCI) patients using a cardiac interventional x-ray system with state-of-the-art image enhancement and x-ray optimization, compared to the current generation x-ray system, and to determine the corresponding impact on clinical image quality. Patient procedure dose area product (DAP) and fluoroscopy duration of 131 PCI patient cases from each x-ray system were compared using a Wilcoxon test on median values. Significant reductions in patient dose (p ≪ 0.001) were found for the new system with no significant change in fluoroscopy duration (p ¼ 0.2); procedure DAP reduced by 64%, fluoroscopy DAP by 51%, and “cine” acquisition DAP by 76%. The image quality of 15 patient angiograms from each x-ray system (30 total) was scored by 75 clinical professionals on a continuous scale for the ability to determine the presence and severity of stenotic lesions; image quality scores were analyzed using a two-sample t -test. Image quality was reduced by 9% (p ≪ 0.01) for the new x-ray system. This demonstrates a substantial reduction in patient dose, from acquisition more than fluoroscopy imaging, with slightly reduced image quality, for the new x-ray system compared to the current generation system. / This research was funded by Philips Healthcare (the Netherlands)

Yes / Cardiologists use x-ray image sequences of the moving heart acquired in real-time to diagnose and treat cardiac patients. The amount of radiation used is proportional to image quality; however, exposure to radiation is damaging to patients and personnel. The amount by which radiation dose can be reduced without compromising patient care was determined. For five patient image sequences, increments of computer-generated quantum noise (white + colored) were added to the images, frame by frame using pixel-to-pixel addition, to simulate corresponding increments of dose reduction. The noise adding software was calibrated for settings used in cardiac procedures, and validated using standard objective and subjective image quality measurements. The degraded images were viewed next to corresponding original (not degraded) images in a two-alternativeforced- choice staircase psychophysics experiment. Seven cardiologists and five radiographers selected their preferred image based on visualization of the coronary arteries. The point of subjective equality, i.e., level of degradation where the observer could not perceive a difference between the original and degraded images, was calculated; for all patients the median was 33% 15% dose reduction. This demonstrates that a 33% 15% increase in image noise is feasible without being perceived, indicating potential for 33% 15% dose reduction without compromising patient care. / Funded in part by Philips Healthcare, the Netherlands. Part of this work has been performed in the project PANORAMA, co-funded by grants from Belgium, Italy, France, the Netherlands, and the United Kingdom, and the ENIAC Joint Undertaking.