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Item Robust Cardiac Function Assessment in 4D PC-MRI Data(The Eurographics Association, 2014) Kƶhler, Benjamin; Preim, Uta; Gutberlet, Matthias; Fischbach, Katharina; Preim, Bernhard; Ivan Viola and Katja Buehler and Timo RopinskiFour-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) is a relatively young image modality that allows the non-invasive acquisition of time-resolved, three-dimensional blood flow information. Stroke volumes and regurgitation fractions are two of the main measures to assess the cardiac function and severity of pathologies. The flow volumes in forward and backward direction through a plane inside the vessel are required for their quantification. Unfortunately, the calculations are highly sensitive towards the plane's angulation since orthogonally passing flow is considered. This often leads to physiologically implausible results. In this work, a robust quantification method is introduced to overcome this problem. Collaborating radiologists and cardiologists were carefully observed while estimating stroke volumes in various healthy volunteer and patient datasets with conventional quantification. This facilitated the automatization of their approach which, in turn, allows to derive statistical information about the plane angulation sensitivity. Moreover, the experts expect a continuous decrease of the stroke volume along the vessel course after a peak value above the aortic valve. Conventional methods are often unable to produce this behavior. Thus, we present a procedure to fit a function that ensures such physiologically plausible results. In addition, the technique was adapted for the robust quantification of regurgitation fractions. The performed qualitative evaluation shows the capability of our method to support diagnosis, a parameter evaluation confirms the robustness. Vortex flow was identified as main cause for quantification uncertainties.Item Comparative Evaluation of Feature Line Techniques for Shape Depiction(The Eurographics Association, 2014) Lawonn, Kai; Baer, Alexandra; Saalfeld, Patrick; Preim, Bernhard; Jan Bender and Arjan Kuijper and Tatiana von Landesberger and Holger Theisel and Philipp UrbanThis paper presents a qualitative evaluation of feature line techniques on various surfaces. We introduce the most commonly used feature lines and compare them. The techniques were analyzed with respect to the degree of realism in comparison with a shaded image with respect to the aesthetic impression they create. First, a pilot study with 20 participants was conducted to make an inquiry about their behavior and the duration. Based on the result of the pilot study, the final evaluation was carried out with 129 participants. We evaluate and interpret the trial results by using the Schulze method and give recommendations for which kind of surface, which feature line technique is most appropriate.Item A Comparative User Study of a 2D and an Autostereoscopic 3D Display for a Tympanoplastic Surgery(The Eurographics Association, 2014) Baer, Alexandra; Huebler, Antje; Saalfeld, Patrick; Cunningham, Douglas; Preim, Bernhard; Ivan Viola and Katja Buehler and Timo RopinskiThis paper presents the design and execution of a comparative experimental between-participant study with 42 participants. We investigated depth perception comparing a 2D display with a glasses-free 3D autostereoscopic display in detail and conducted a follow-up study with the new 3D zSpace technology including a stylus as input device. This work comprises the design of a tympanoplastic training scenario used as the study's "real world task". Participants had to position a prosthesis implant to reconstruct the ossicular chain and thus a patient's hearing ability. The study revealed an overwhelming support of the 3D autostereoscopic display compared to a 2D display regarding depth judgment, task completion time and the number of required scene and prosthesis interactions.Item Bilateral Depth Filtering for Enhanced Vessel Reformation(The Eurographics Association, 2014) Kretschmer, Jan; Preim, Bernhard; Stamminger, Marc; N. Elmqvist and M. Hlawitschka and J. KennedyCurved Planar Reformation is a powerful visualization technique for the diagnosis of vascular diseases. It allowsan accurate centerline-driven investigation of vessel lumen while providing valuable anatomical context.Extended methods like Multipath Curved Planar Reformation, Centerline Reformation or Curved Surface Reformationprovide additional flexibility by condensing entire vascular systems into rotatable views. Unfortunately, allthese methods produce depth discontinuities because they operate in a projective fashion. While large discontinuitiesprovide valuable hints about distinct anatomical contexts, small discontinuities, which frequently arise, havedistracting effects on the visualization result and do not contribute significant information. In this paper we presenta bilateral filtering technique which allows to selectively remove depth discontinuities without affecting discontinuitiesthat carry information. The presented approach significantly improves the quality of vessel reformations,can be applied at interactive frame rates and is orthogonal to existing methods.Item Comparative Blood Flow Visualization for Cerebral Aneurysm Treatment Assessment(The Eurographics Association and John Wiley and Sons Ltd., 2014) Pelt, Roy van; Gasteiger, Rocco; Lawonn, Kai; Meuschke, Monique; Preim, Bernhard; H. Carr, P. Rheingans, and H. SchumannA pathological vessel dilation in the brain, termed cerebral aneurysm, bears a high risk of rupture, and is associated with a high mortality. In recent years, incidental findings of unruptured aneurysms have become more frequent, mainly due to advances in medical imaging. The pathological condition is often treated with a stent that diverts the blood flow from the aneurysm sac back to the original vessel. Prior to treatment, neuroradiologists need to decide on the optimal stent configuration and judge the long-term rupture risk, for which blood flow information is essential. Modern patient-specific simulations can model the hemodynamics for various stent configurations, providing important indicators to support the decision-making process. However, the necessary visual analysis of these data becomes tedious and time-consuming, because of the abundance of information. We introduce a comprehensive comparative visualization that integrates morphology with blood flow indicators to facilitate treatment assessment. To deal with the visual complexity, we propose a details-on-demand approach, combining established medical visualization techniques with innovative glyphs inspired by information visualization concepts. In an evaluation we have obtained informal feedback from domain experts, gauging the value of our visualization.Item Interactive Labeling of Toponome Data(The Eurographics Association, 2014) Oeltze-Jafra, Steffen; Pieper, Franz; Hillert, Reyk; Preim, Bernhard; Schubert, Walter; Ivan Viola and Katja Buehler and Timo RopinskiBiological multi-channel microscopy data are often characterized by a high local entropy and phenotypically identical structures covering only a few pixels and forming disjoint regions spread over, e.g., a cell or a tissue section. Toponome data as an example, comprise a fluorescence image (channel) per protein affinity reagent, and capture the location and spatial distribution of proteins in cells and tissues. Biologists investigate such data using a region-of-interest in an image view and a linked view displaying information aggregated or derived from the channels. The cognitive effort of moving the attention back and forth between the views is immense. We present an approach for the in-place annotation of multi-channel microscopy data in 2D views. We combine dynamic excentric labeling and static necklace maps to cope with the special characteristics of these data. The generated annotations support the biologists in visually exploring multi-channel information directly in its spatial context. A label is generated per unique phenotype included in a flexible, moveable focus region. The labels are organized in a circular fashion around the focus region. On demand, a nested labeling can be generated by displaying a second ring of labels which represents the channels characterizing the focused phenotypes. We demonstrate our approach by toponome data of a rhabdomyosarcoma cell line and a prostate tissue section.Item Coherent View-Dependent Streamlines for Understanding Blood Flow(The Eurographics Association, 2014) Lawonn, Kai; Günther, Tobias; Preim, Bernhard; N. Elmqvist and M. Hlawitschka and J. KennedyThe expressive visualization of (time-dependent) 3D blood flow along with the vessel wall is essential for understandingvascular diseases. However, the high complexity of the underlying flow data makes the explorationchallenging. For the biomedical research, it is necessary to provide methods that allow for rapid flow comprehension,ideally by emphasizing relevant flow characteristics. Therefore, we present a fast approach that visualizesstreamlines in a view-dependent way, while taking relevant flow features into consideration. For this, we adapt awell-established non-photorealistic rendering technique - suggestive contours - for surface meshes to streamlineillustrations. The advantages of our approach are confirmed in an informal user feedback with domain experts,who were able to comprehend the overall flow behavior faster.Item Line Integral Convolution for Real-Time Illustration of Molecular Surface Shape and Salient Regions(The Eurographics Association and John Wiley and Sons Ltd., 2014) Lawonn, Kai; Krone, Michael; Ertl, Thomas; Preim, Bernhard; H. Carr, P. Rheingans, and H. SchumannWe present a novel line drawing algorithm that illustrates surfaces in real-time to convey their shape. We use line integral convolution (LIC) and employ ambient occlusion for illustrative surface rendering. Furthermore, our method depicts salient regions based on the illumination gradient. Our method works on animated surfaces in a frame-coherent manner. Therefore, it yields an illustrative representation of time-dependent surfaces as no preprocessing step is needed. In this paper, the method is used to highlight the structure of molecular surfaces and to illustrate important surface features like cavities, channels, and pockets. The benefit of our method was evaluated with domain experts. We also demonstrate the applicability of our method to medical visualization.Item Survey of Labeling Techniques in Medical Visualizations(The Eurographics Association, 2014) Oeltze-Jafra, Steffen; Preim, Bernhard; Ivan Viola and Katja Buehler and Timo RopinskiAnnotations of relevant structures and regions are crucial in diagnostics, treatment planning, medical team meetings as well as in medical education. They serve to focus discussions, present results of collaborative decision making, record and forward diagnostic findings, support orientation in complex or unfamiliar views on the data, and study anatomy. Different techniques have been presented for labeling the original data in 2D slice views, surface representations of structures extracted from the data, e.g., organs and vasculature, and 3D volume rendered representations of the data. All aim at a clear visual association of labels and structures, visible and legible labels, and a fast and aesthetic labeling while considering individual properties of the data and its representation and tackling various issues, e.g., occlusion of structures by labels, overlapping labels, and crossings of lines connecting labels with structures. We survey the medical labeling work and propose a classification with respect to the employed labeling technique. We give guidelines for choosing a technique dependent on the data representation, e.g., surface rendering or slice view, the type of structures to be labeled, and the individual requirements on an effective label layout.Item Adaptive Surface Visualization of Vessels with Animated Blood Flow(The Eurographics Association and John Wiley and Sons Ltd., 2014) Lawonn, Kai; Gasteiger, Rocco; Preim, Bernhard; Oliver Deussen and Hao (Richard) ZhangThe investigation of hemodynamic information for the assessment of cardiovascular diseases (CVDs) gained importance in recent years. Improved flow measuring modalities and computational fluid dynamics (CFD) simulations yield in reliable blood flow information. For a visual exploration of the flow information, domain experts are used to investigate the flow information combined with its enclosed vessel anatomy. Since the flow is spatially embedded in the surrounding vessel surface, occlusion problems have to be resolved. A visual reduction of the vessel surface that still provides important anatomical features is required. We accomplish this by applying an adaptive surface visualization inspired by the suggestive contour measure. Furthermore, an illustration is employed to highlight the animated pathlines and to emphasize nearby surface regions. Our approach combines several visualization techniques to improve the perception of surface shape and depth. Thereby, we ensure appropriate visibility of the embedded flow information, which can be depicted with established or advanced flow visualization techniques. We apply our approach to cerebral aneurysms and aortas with simulated and measured blood flow. An informal user feedback with nine domain experts, we confirm the advantages of our approach compared with existing methods, e.g. semiātransparent surface rendering. Additionally, we assessed the applicability and usefulness of the pathline animation with highlighting nearby surface regions.The investigation of hemodynamic information for the assessment of cardiovascular diseases (CVD) gained importance in recent years. Improved flow measuring modalities and computational fluid dynamics (CFD) simulations yield in reliable blood flow information. For a visual exploration of the flow information, domain experts are use to investigate the flow information combined with its enclosed vessel anatomy. Since the flow is spatially embedded in the surrounding vessel surface, occlusion problems have to be resolved. A visual reduction of the vessel surface that still provides important anatomical features is required. We accomplish this by applying an adaptive surface visualization inspired by the suggestive contour measure.