83 research outputs found
Multiple intracranial aneurysms: a direct hemodynamic comparison between ruptured and unruptured vessel malformations
No full textTruncation artifacts caused by the patient table in polyenergetic statistical reconstruction on real C-arm CT data
No full text3D-localization of anatomic structures in tomographic images from optical flow of projection images
No full textDer Ellbogenqualitäts-Index (EQ) als neue Methode in der Bekämpfung der Ellbogendysplasie (ED) beim Hund : eine kritische Analyse der Methode
No full textZiel dieser Arbeit ist die qualitative Überprüfung der Messmethode von Mues und Beuing zur Bestimmung der Ellbogenqualität (EQ-Index) im Rahmen der Ellbogendysplasie (ED) beim Hund. Beim EQ-Index handelt es sich um einen Selektionsindex, welcher aus vier Ellbogengelenkswinkeln konstruiert wird und den Genotyp für das ererbte Arthroserisiko umschreibt. Die Überprüfung erfolgte an Ellbogen-Röntgenbildern mit ED-Gutachten folgender drei Hunderassen: Golden Retriever (GR), Labrador Retriever (LR) und Deutscher Schäferhund. Methodik und Einflüsse auf die Winkelvermessungstechnik am Ellbogen wurden anhand folgender Parameter geprüft: Bildqualität der Röntgenbilder, ED-Grad, Ellbogenprojektion, Gelenks-Messpunkte und Wiederholbarkeiten. Zusammenhänge zwischen ED-Grad und EQ-Index wurde anhand der drei Hunderassen mittels ED-Status, genetischer Analysen und Gelenkswinkelmessungen überprüft. Zur exakten Bestimmung des EQ-Index sollten nur qualitativ gute Röntgenbilder benutzt werden. Die Winkelmessungen und der EQ-Index werden durch arthrotische Zubildungen, unterschiedliche Ellbogenprojektionen, Haltung der Gliedmasse und Verschiebung der Messpunkte im Gelenk beeinflusst. Messwiederholungen zeigen bei den Gelenkswinkeln eine gute und beim EQ-Index eine genügende Korrelation. Beim LR und GR ist die Heritabilität des EQ-Index fast doppelt so hoch wie bei der ED. Die optimierten EQ-Indizes zeigen beim LR und GR mit – 0,55 eine bessere Korrelation zum ED-Genotyp als das ED-Gutachten mit 0,36. Elbow quality-index (EQ) as a new method in the control of elbow dysplasia (ED) in dogs – a critical analysis of the method
The purpose of this study is the qualitative verification of the measurement method for the determination of the elbow quality (EQ-Index), developed by Mues and Beuing, in the context of the elbow dysplasia (ED) in the dog. The EQ-Index is a selection-index constructed by four angles of the elbow joint and it characterizes the genotype for the inherited development of arthrosis. The verification was performed on the basis of the ED certified elbow radiographs of the following breeds: Golden Retriever (GR), Labrador Retriever (LR) and German Shepherd Dog. The method and the influences on the technique of the elbow angle measurement were verified by the following parameters: quality of the radiographs, ED status (grade), elbow projection, measuring points and the reproducibility. The correlation between ED-grade and EQ-Index in the three breeds was investigated by ED status, genetic analysis and joint angle measurements. Only radiographs of good quality should be used for a precise determination of the EQ-index. The angle measurements and the EQ-index are affected by arthrosis (osteophyte formation), different elbow projections, positioning of the limb and displacement of the measuring points within the joint. The reproducibility for the angle measurements is good and for the EQ- index sufficient. The heritability of the EQ-index is almost twice as much the ED-grade. For LR and GR optimized EQ-indeces show a better correlation (- 0,55) to the ED genotype than the ED-grade (0,36)
Automatic Viewpoint Selection for Exploration of Time-Dependent Cerebral Aneurysm Data
No full textThis paper presents an automatic selection of viewpoints, forming a camera path, to support the exploration of cerebral aneurysms. Aneurysms bear the risk of rupture with fatal consequences for the patient. For the rupture risk evaluation, a combined investigation of morphological and hemodynamic data is necessary. However, the extensive nature of the time-dependent data complicates the analysis. During exploration, domain experts have to manually determine appropriate views, which can be a tedious and time-consuming process. Our method determines optimal viewpoints automatically based on input data such as wall thickness or pressure. The viewpoint selection is modeled as an optimization problem. Our technique is applied to five data sets and we evaluate the results with two domain experts by conducting informal interviews.</p
Multiple Aneurysms AnaTomy CHallenge 2018 (MATCH)—Phase Ib: Effect of morphology on hemodynamics
No full textBackgroundImage-based blood flow simulations have been increasingly applied to investigate intracranial aneurysm (IA) hemodynamics. However, the acceptance among physicians remains limited due to the high variability in the underlying assumptions and quality of results.MethodsTo evaluate the vessel segmentation as one of the most important sources of error, the international Multiple Aneurysms AnaTomy CHallenge 2018 (MATCH) was announced. 26 research groups from 13 different countries segmented three datasets, which contained five IAs in total. Based on these segmentations, 73 time-dependent blood flow simulations under consistent conditions were carried out. Afterwards, relevant flow and shear parameters (e.g., neck inflow rate, parent vessel flow rate, spatial mean velocity, and wall shear stress) were analyzed both qualitatively and quantitatively.ResultsRegarding the entire vasculature, the variability of the segmented vessel radius is 0.13 mm, consistent and independent of the local vessel radius. However, the centerline velocity shows increased variability in more distal vessels. Focusing on the aneurysms, clear differences in morphological and hemodynamic parameters were observed. The quantification of the segmentation-induced variability showed approximately a 14% difference among the groups for the parent vessel flow rate. Regarding the mean aneurysmal velocity and the neck inflow rate, a variation of 30% and 46% was observed, respectively. Finally, time-averaged wall shear stresses varied between 28% and 51%, depending on the aneurysm in question.ConclusionsMATCH reveals the effect of state-of-the-art segmentation algorithms on subsequent hemodynamic simulations for IA research. The observed variations may lead to an inappropriate interpretation of the simulation results and thus, can lead to inappropriate conclusions by physicians. Therefore, accurate segmentation of the region of interest is necessary to obtain reliable and clinically helpful flow information.</div
Glyph-Based Comparative Stress Tensor Visualization in Cerebral Aneurysms
No full textWe present the first visualization tool that enables a comparative depiction of structural stress tensor data for vessel walls of cerebral aneurysms. Such aneurysms bear the risk of rupture, whereas their treatment also carries considerable risks for the patient. Medical researchers emphasize the importance of analyzing the interaction of morphological and hemodynamic information for the patient-specific rupture risk evaluation and treatment analysis. Tensor data such as the stress inside the aneurysm walls characterizes the interplay between the morphology and blood flow and seems to be an important rupture-prone criterion. We use different glyph-based techniques to depict local stress tensors simultaneously and compare their applicability to cerebral aneurysms in a user study. We thus offer medical researchers an effective visual exploration tool to assess the aneurysm rupture risk.We developed a GPU-based implementation of our techniques with a flexible interactive data exploration mechanism. Our depictions are designed in collaboration with domain experts, and we provide details about the evaluation.Computer Graphics ForumBiomedical Visualization36
The FAUST framework: Free-form annotations on unfolding vascular structures for treatment planning
No full textA complete scheme of empirical beam hardening correction using Grangeat consistency condition
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