Manifold learning for image-based gating of intravascular ultrasound(IVUS) pullback sequences

Intravascular Ultrasound(IVUS) is an imaging technology which provides cross-sectional images of internal coronary vessel struc- tures. The IVUS frames are acquired by pulling the catheter back with a motor running at a constant speed. However, during the pullback, some artifacts occur due to the beating heart. These artifacts cause inaccu- rate measurements for total vessel and lumen volume and limitation for further processing. Elimination of these artifacts are possible with an ECG (electrocardiogram) signal, which determines the time interval cor- responding to a particular phase of the cardiac cycle. However, using ECG signal requires a special gating unit, which causes loss of impor- tant information about the vessel, and furthermore, ECG gating function may not be available in all clinical systems. To address this problem, we propose an image-based gating technique based on manifold learning. Quantitative tests are performed on 3 different patients, 6 different pull- backs and 24 different vessel cuts. In order to validate our method, the results of our method are compared to those of ECG-Gating method

Software Sustainability: Research and Practice from a Software Architecture Viewpoint

Context: Modern societies are highly dependent on complex, large-scale, software-intensive systems that increasingly operate within an environment of continuous availability, which is challenging to maintain and evolve in response to the inevitable changes in stakeholder goals and requirements of the system. Software architectures are the foundation of any software system and provide a mechanism for reasoning about core software quality requirements. Their sustainability – the capacity to endure in changing environments – is a critical concern for software architecture research and practice. Problem: Accidental software complexity accrues both naturally and gradually over time as part of the overall software design and development process. From a software architecture perspective, this allows several issues to overlap including, but not limited to: the accumulation of technical debt design decisions of individual components and systems leading to coupling and cohesion issues; the application of tacit architectural knowledge resulting in unsystematic and undocumented design decisions; architectural knowledge vaporisation of design choices and the continued ability of the organization to understand the architecture of its systems; sustainability debt and the broader cumulative effects of flawed architectural design choices over time resulting in code smells, architectural brittleness, erosion, and drift, which ultimately lead to decay and software death. Sustainable software architectures are required to evolve over the entire lifecycle of the system from initial design inception to end-of-life to achieve efficient and effective maintenance and evolutionary change. Method: This article outlines general principles and perspectives on sustainability with regards to software systems to provide a context and terminology for framing the discourse on software architectures and sustainability. Focusing on the capacity of software architectures and architectural design choices to endure over time, it highlights some of the recent research trends and approaches with regards to explicitly addressing sustainability in the context of software architectures. Contribution: The principal aim of this article is to provide a foundation and roadmap of emerging research themes in the area of sustainable software architectures highlighting recent trends, and open issues and research challenges

Deformable Registration of 3D Vessel Structures to a Single Projection Image

Alignment of angiographic preoperative 3D scans to intraoperative 2D projections is an important issue for 3D depth perception and navigation during interventions. Currently, in a setting where only one 2D projection is available, methods employing a rigid transformation model present the state of the art for this problem. In this work, we introduce a method capable of deformably registering 3D vessel structures to a respective single projection of the scene. Our approach addresses the inherent ill-posedness of the problem by incorporating a priori knowledge about the vessel structures into the formulation. We minimize the distance between the 2D points and corresponding projected 3D points together with regularization terms encoding the properties of length preservation of vessel structures and smoothness of deformation. We demonstrate the performance and accuracy of the proposed method by quantitative tests on synthetic examples as well as real angiographic scenes

Planning and Intraoperative Visualization of Liver Catheterizations: New CTA Protocol and 2D-3D Registration Method

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New CTA Protocol and 2D-3D Registration Method for Liver Catheterization

International audience2D-3D registration for angiographic liver interventions is an unsolved problem mainly because of two reasons. First, a suitable protocol for Computed Tomography Angiography (CTA) to contrast liver arteries is not used in clinical practice. Second, an adequate registration algorithm which addresses the difficult task of aligning deformed vessel structures has not been developed yet. We address the first issue by introducing an angiographic CT scanning phase and thus create a strong link between radiologists and interventionalists. The scan visualizes arteries similar to the vasculature captured with an intraoperative C-arm acquiring Digitally Subtracted Angiograms (DSAs). Furthermore, we propose a registration algorithm using the new CT phase that aligns arterial structures in two steps: a) Initialization of one corresponding feature using vessel diameter information, b) optimization on three rotational and one translational parameter to register vessel structures that are represented as centerline graphs. We form a space of good features by iteratively creating new graphs from projected centerline images and by restricting the correspondence search only on branching points (the vertices) of the vessel tree. This algorithm shows good convergence and proves to be robust against deformation changes, which is demonstrated through studies on one phantom and three patients