Robust point correspondence applied to two and three-dimensional image registration

Accurate and robust correspondence calculations are very important in many medical and biological applications. Often, the correspondence calculation forms part of a rigid registration algorithm, but accurate correspondences are especially important for elastic registration algorithms and for quantifying changes over time. In this paper, a new correspondence calculation algorithm, CSM (correspondence by sensitivity to movement), is described. A robust corresponding point is calculated by determining the sensitivity of a correspondence to movement of the point being matched. If the correspondence is reliable, a perturbation in the position of this point should not result in a large movement of the correspondence. A measure of reliability is also calculated. This correspondence calculation method is independent of the registration transformation and has been incorporated into both a 2D elastic registration algorithm for warping serial sections and a 3D rigid registration algorithm for registering pre and postoperative facial range scans. These applications use different methods for calculating the registration transformation and accurate rigid and elastic alignment of images has been achieved with the CSM method. It is expected that this method will be applicable to many different applications and that good results would be achieved if it were to be inserted into other methods for calculating a registration transformation from correspondence

Effectiveness of Visualisations for Detection of Errors in Segmentation of Blood Vessels

Vascular disease diagnosis often requires a precise segmentation of the vessel lumen. When 3D (Magnetic Resonance Angiography, MRA, or Computed Tomography Angiography, CTA) imaging is available, this can be done automatically, but occasional errors are inevitable. So, the segmentation has to be checked by clinicians. This requires appropriate visualisation techniques. A number of visualisation techniques exist, but there has been little in the way of user studies that compare the different alternatives. In this study we examine how users interact with several basic visualisations, when performing a visual search task, checking vascular segmentation correctness of segmented MRA data. These visualisations are: direct volume rendering (DVR), isosurface rendering, and curved planar reformatting (CPR). Additionally, we examine if visual highlighting of potential errors can help the user find errors, so a fourth visualisation we examine is DVR with visual highlighting. Our main findings are that CPR performs fastest but has higher error rate, and there are no significant differences between the other three visualisations. We did find that visual highlighting actually has slower performance in early trials, suggesting that users learned to ignore them

Context Preserving Focal Probes for Exploration of Volumetric Medical Datasets

During real-time medical data exploration using volume rendering, it is often difficult to enhance a particular region of interest without losing context information. In this paper, we present a new illustrative technique for focusing on a user-driven region of interest while preserving context information. Our focal probes define a region of interest using a distance function which controls the opacity of the voxels within the probe, exploit silhouette enhancement and use non-photorealistic shading techniques to improve shape depiction.187-19

Can Real Social Epistemic Networks Deliver the Wisdom of Crowds?

In this paper, we explain and showcase the promising methodology of testimonial network analysis and visualization for experimental epistemology, arguing that it can be used to gain insights and answer philosophical questions in social epistemology. Our use case is the epistemic community that discusses vaccine safety primarily in English on Twitter. In two studies, we show, using both statistical analysis and exploratory data visualization, that there is almost no neutral or ambivalent discussion of vaccine safety on Twitter. Roughly half the accounts engaging with this topic are pro-vaccine, while the other half are con-vaccine. We also show that these two camps rarely engage with one another, and that the con-vaccine camp has greater epistemic reach and receptivity than the pro-vaccine camp. In light of these findings, we question whether testimonial networks as they are currently constituted on popular fora such as Twitter are living up to their promise of delivering the wisdom of crowds. We conclude by pointing to directions for further research in digital social epistemology

Use of recurrence quantification analysis to examine associations between changes in text structure across an expressive writing intervention and reductions in distress symptoms in women wth breast cancer

The current study presents an exploratory analysis of using Recurrence Quantification Analysis (RQA) to analyze text data from an Expressive Writing Intervention (EWI) for Danish women treated for Breast Cancer. The analyses are based on the analysis of essays from a subsample with the average age 54.6 years (SD = 9.0), who completed questionnaires for cancer-related distress (IES) and depression symptoms (BDI-SF). The results show a significant association between an increase in recurrent patterns of text structure from first to last writing session and a decrease in cancer-related distress at 3 months post-intervention. Furthermore, the change in structure from first to last essay displayed a moderate, but significant correlation with change in cancer-related distress from baseline to 9 months post-intervention. The results suggest that changes in recurrence patterns of text structure might be an indicator of cognitive restructuring that leads to amelioration of cancer-specific distress

Contextual Sensitivity in Grounded Theory: The Role of Pilot Studies

Grounded Theory is an established methodological approach for context specific inductive theory building. The grounded nature of the methodology refers to these specific contexts from which emergent propositions are drawn. Thus, any grounded theory study requires not only theoretical sensitivity, but also a good insight on how to design the research in the human activity systems to be studied. The lack of this insight may result in inefficient theoretical sampling or even erroneous purposeful sampling. These problems would not necessarily be critical, as it could be argued that through the elliptical process that characterizes grounded theory, remedial loops would always bring the researcher to the core of the theory. However, these elliptical remedial processes can take very long periods of time and result in catastrophic delays in research projects. As a strategy, this paper discusses, contrasts and compares the use of pilot studies in four different grounded theory projects. Each pilot brought different insights about the context, resulting in changes of focus, guidance to improve data collection instruments and informing theoretical sampling. Additionally, as all four projects were undertaken by researchers with little experience of inductive approaches in general and grounded theory in particular, the pilot studies also served the purpose of training in interviewing, relating to interviewees, memoing, constant comparison and coding. This last outcome of the pilot study was actually not planned initially, but revealed itself to be a crucial success factor in the running of the projects. The paper concludes with a theoretical proposition for the concept of contextual sensitivity and for the inclusion of the pilot study in grounded theory research designs

Trends and concerns in digital cartography

CISRG discussion paper ;

Healthcare financing in OECD countries beyond the public-private split

Background: Studies of long-term trends in the healthcare financing mix generally focus on a dichotomous concept discerning public from private funding sources. More detailed analyses of the funding mix tend to be restricted to a small number of cases or do rarely examine time trends. Aim: This paper enhances the existing body of literature by developing and applying a trichotomous concept for healthcare funding, distinguishing taxes, contributions, and private sources. This includes a new aggregated indicator for the mix of three financing sources and its graphical representation. Methods: The study mainly builds upon OECD Health Data 2011. We measure changes in the funding mix since 1972 as its distance from a funding mix that equally draws upon taxes, contributions and private sources. Results: Up to 1980, the OECD healthcare systems move toward ideal-typical financing schemes. Between 1980 and 2000, the funding mix hybridizes mainly driven by privatization processes in NHS and social insurance countries and ongoing switch-over-processes between these two healthcare system types. Since 2000, OECD countries again tend toward ideal-typical funding schemes. Discussion: We use the framework for institutional change developed by Streeck and Thelen. The quantitative approach highlights changes in terms of displacement, layering, and drift but fails to fully reveal conversion processes. Therefore, further qualitative research is needed to capture not only shifts between the funding sources but also more gradual changes within them. Conclusion: The back-and-forth development of the trichotomous funding mix challenges assumptions of a universal trend toward hybrid financing structures. -- Rahmen: Arbeiten, die langfristige Trends des Finanzierungsmix von Gesundheitsausga-ben untersuchen, basieren in der Regel auf einem dichotomen Konzept, das öffentliche und private Quellen unterscheidet. Detailliertere Studien zum disaggregierten Finanzierungsmix sind zumeist auf kleine Fallzahlen beschränkt oder betrachten keine Entwicklungen über Zeit. Ziel: Das Arbeitspapier entwickelt ein trichotomes Finanzierungskonzept, das zwischen Steuern, Beiträgen und privaten Quellen unterscheidet und wendet dieses auf OECD-Gesundheitssysteme an. Hierfür wird ein neuer Hybriditätsindex gebildet, der den Finanzierungsmix eines Landes beschreibt und graphisch verortet. Methoden: Wir messen die Veränderungen im Finanzierungsmix seit 1972 als Distanz von einem hypothetischen Finanzierungsmix, der sich jeweils zu einem Drittel auf Steuern, Beiträge und privaten Ausgaben stützt. Als Quelle dienen die OECD Health Data 2011 und ergänzende nationale Statistiken. Ergebnisse: Bis etwa 1980 steuern die OECD-Gesundheitssysteme auf unterschiedliche idealtypische Finanzierungsmodelle zu. Zwischen 1980 und 2000 beobachten wir eine Hybridisierung der Finanzierung von Gesundheitsausgaben, die vorwiegend auf Privatisierungsprozesse in den NHS- und Sozialversicherungsländern zurückgeführt werden kann. Überdies tragen einzelne Länder durch einen inkrementellen Übergang vom Sozialversicherungssystem zum NHS zunächst zur Hybridisierung bei. Seit 2000 neigen die OECD-Länder wieder idealtypischen Finanzierungsstrukturen zu. Diskussion: Wir analysieren die Befunde anhand der von Streeck und Thelen entwickelten Formen institutionellen Wandels. Der Hybridisierungsindex verdeutlicht Wandel in Form von Displacement, Layering und Drift, während Conversion-Prozesse nicht vollständig abgebildet werden können. Hierfür bedarf es qualitativer Analysen, die nicht nur Verschiebungen zwischen Finanzierungsarten sondern graduelle Veränderungen innerhalb einer Finanzierungsart erfassen. Fazit: Der Wandel zwischen Hybridisierungsphasen und Phasen der Stärkung idealtypischer Finanzierung deutet darauf hin, dass funktionale Annahmen eines langfristigen Trends zu hybriden Finanzierungsstrukturen zu kurz greifen.