Agreement between single plane and biplane derived angiographic fractional flow reserve in patients with intermediate coronary artery stenosis.

Fractional flow reserve (FFR) is often used to evaluate the physiological severity of intermediate coronary stenoses, but less-invasive assessment methods are desirable. We evaluated the feasibility of angiographic FFR (angioFFR) calculated from two projections acquired simultaneously by a biplane C-arm system and angioFFR calculated from two projections acquired independently by one plane of the same biplane C-arm system. AngioFFR was validated against FFR in terms of detection of hemodynamically relevant coronary artery stenoses.

An Automated Workflow for Hemodynamic Computations in Cerebral Aneurysms.

In recent years, computational fluid dynamics (CFD) has become a valuable tool for investigating hemodynamics in cerebral aneurysms. CFD provides flow-related quantities, which have been shown to have a potential impact on aneurysm growth and risk of rupture. However, the adoption of CFD tools in clinical settings is currently limited by the high computational cost and the engineering expertise required for employing these tools, e.

Rupture Risk of Small Unruptured Intracranial Aneurysms in Japanese Adults.

Background and Purpose- Therapeutic decision making for small unruptured intracranial aneurysms (<10 mm) is difficult. We aimed to develop a rupture risk model for small intracranial aneurysms in Japanese adults, including clinical, morphological, and hemodynamic parameters. Methods- We analyzed 338 small unruptured aneurysms; 35 ruptured during the observation period, and 303 remained stable.

Viewpoint planning for quantitative coronary angiography.

Purpose: In coronary angiography, the condition of myocardial blood supply is assessed by analyzing 2-D X-ray projections of contrasted coronary arteries. This is done using a flexible C-arm system. Due to the X-ray immanent dimensionality reduction projecting the 3-D scene onto a 2-D image, the viewpoint is critical to guarantee an appropriate view onto the affected artery and, thus, enable reliable diagnosis.

Tomographic particle image velocimetry for the validation of hemodynamic simulations in an intracranial aneurysm.

Image-based blood flow simulations can provide detailed hemodynamic information in diseased vessels such as intracranial aneurysms. However, validation is essential to evaluate the accuracy of these computations and further improve their acceptance among physicians. In this regard, tomographic particle image velocimetry was used to measure the flow characteristics in a patient specific aneurysm phantom model.

Bringing hemodynamic simulations closer to the clinics: a CFD prototype study for intracranial aneurysms.

Computational Fluid Dynamics enables the investigation of patient-specific hemodynamics for rupture predictions and treatment support of intracranial aneurysms. However, due to numerous simplifications to decrease the computations effort, clinical applicability is limited until now. To overcome this situation a clinical research software prototype was tested that can be easily operated by attending physicians.

Verification of a research prototype for hemodynamic analysis of cerebral aneurysms.

Owing to its clinical importance, there has been a growing body of research on understanding the hemodynamics of cerebral aneurysms. Traditionally, this work has been performed using general-purpose, state-of-the-art commercial solvers. This has meant requiring engineering expertise for making appropriate choices on the geometric discretization, time-step selection, choice of boundary conditions etc.

Patient-individualized boundary conditions for CFD simulations using time-resolved 3D angiography.

Purpose: Hemodynamic simulations are of increasing interest for the assessment of aneurysmal rupture risk and treatment planning. Achievement of accurate simulation results requires the usage of several patient-individual boundary conditions, such as a geometric model of the vasculature but also individualized inflow conditions.

Methods: We propose the automatic estimation of various parameters for boundary conditions for computational fluid dynamics (CFD) based on a single 3D rotational angiography scan, also showing contrast agent inflow.

A fully-automatic locally adaptive thresholding algorithm for blood vessel segmentation in 3D digital subtraction angiography.

Subarachnoid hemorrhage due to a ruptured cerebral aneurysm is still a devastating disease. Planning of endovascular aneurysm therapy is increasingly based on hemodynamic simulations necessitating reliable vessel segmentation and accurate assessment of vessel diameters. In this work, we propose a fully-automatic, locally adaptive, gradient-based thresholding algorithm.

Comparison of Fractional Flow Reserve Based on Computational Fluid Dynamics Modeling Using Coronary Angiographic Vessel Morphology Versus Invasively Measured Fractional Flow Reserve.

Invasive fractional flow reserve (FFRinvasive), although gold standard to identify hemodynamically relevant coronary stenoses, is time consuming and potentially associated with complications. We developed and evaluated a new approach to determine lesion-specific FFR on the basis of coronary anatomy as visualized by invasive coronary angiography (FFRangio): 100 coronary lesions (50% to 90% diameter stenosis) in 73 patients (48 men, 25 women; mean age 67 ± 9 years) were studied. On the basis of coronary angiograms acquired at rest from 2 views at angulations at least 30° apart, a PC-based computational fluid dynamics modeling software used personalized boundary conditions determined from 3-dimensional reconstructed angiography, heart rate, and blood pressure to derive FFRangio.

A Fourier-based approach to the angiographic assessment of flow diverter efficacy in the treatment of cerebral aneurysms.

Flow diversion is an emerging endovascular treatment option for cerebral aneurysms. Quantitative assessment of hemodynamic changes induced by flow diversion can aid clinical decision making in the treatment of cerebral aneurysms. In this article, besides summarizing past key research efforts, we propose a novel metric for the angiographic assessment of flow diverter deployments in the treatment of cerebral aneurysms.

Hemodynamics at the ostium of cerebral aneurysms with relation to post-treatment changes by a virtual flow diverter: a computational fluid dynamics study.

Computational fluid dynamics (CFD) techniques have been refined for modeling the hemodynamics in cerebral aneurysms. Recent interest has focused on understanding hemodynamic changes by treatment with a flow diverter (FD), i.e.

A workflow for patient-individualized virtual angiogram generation based on CFD simulation.

Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms.

Tetrahedral vs. polyhedral mesh size evaluation on flow velocity and wall shear stress for cerebral hemodynamic simulation.

Haemodynamic factors, in particular wall shear stresses (WSSs) may have significant impact on growth and rupture of cerebral aneurysms. Without a means to measure WSS reliably in vivo, computational fluid dynamic (CFD) simulations are frequently employed to visualise and quantify blood flow from patient-specific computational models. With increasing interest in integrating these CFD simulations into pretreatment planning, a better understanding of the validity of the calculations in respect to computation parameters such as volume element type, mesh size and mesh composition is needed.

Impact of tear location on hemodynamics in a type B aortic dissection investigated with computational fluid dynamics.

Stanford type B aortic dissections (TB-AD), which split the descending aorta in a true and false lumen, have better in-hospital survival than type A dissections affecting the ascending aorta. However, short-term and long-term prognosis for the individual patient remains challenging, with one in four patients not surviving after 3 years.

Tetrahedral and polyhedral mesh evaluation for cerebral hemodynamic simulation--a comparison.

Computational fluid dynamic (CFD) based on patient-specific medical imaging data has found widespread use for visualizing and quantifying hemodynamics in cerebrovascular disease such as cerebral aneurysms or stenotic vessels. This paper focuses on optimizing mesh parameters for CFD simulation of cerebral aneurysms. Valid blood flow simulations strongly depend on the mesh quality.

Intravascular optical coherence tomography: comparison with histopathology in atherosclerotic peripheral artery specimens.

Purpose: Intravascular optical coherence tomography (OCT) is a new imaging modality that provides microstructural information on atherosclerotic plaques and has an axial resolution of 10-20 microm. OCT of coronary arteries characterizes different atherosclerotic plaque components by their distinctive signal patterns. Peripheral human arteries were examined ex vivo by means of OCT, and attempts to distinguish among fibrous, lipid-rich, and calcified atherosclerotic plaques were made based on imaging criteria previously established for coronary arteries.