Evaluation of flow changes after telescopic stenting of a giant fusiform aneurysm of the vertebrobasilar junction.

Background: The use of flow-diverters for non-saccular cerebral posterior circulation aneurysms requires complex deployment techniques and is associated with high mortality and morbidity. Therefore, further studies are required to clarify the effect of stenting on post-treatment hemodynamics in such aneurysms. In this study, we evaluated flow alterations in a treated giant fusiform aneurysm of the vertebrobasilar junction and correlated them with the clinical outcome.

Intimal Hyperplasia After Aneurysm Treatment by Flow Diversion.

Background: Flow diverter stents have become a useful tool for treatment of complex intracranial aneurysms. A serious complication is incomplete wall apposition after flow diverter placement. The aim of this study was to present a comprehensive investigation of hemodynamic changes induced by incomplete expansion of a flow diverter.

High-frequency wall vibrations in a cerebral patient-specific aneurysm model.

The presence of high-frequency velocity fluctuations in aneurysms have been confirmed by in-vivo measurements and by several numerical simulation studies. Only a few studies have located and recorded wall vibrations in in-vitro experiments using physiological patient models. In this study, we investigated the wall fluctuations produced by a flowing perfusion fluid in a true-to-scale elastic model of a cerebral fusiform aneurysm using a laser Doppler vibrometer (LDV).

Phase-contrast MRI versus numerical simulation to quantify hemodynamical changes in cerebral aneurysms after flow diverter treatment.

Cerebral aneurysms are a major risk factor for intracranial bleeding with devastating consequences for the patient. One recently established treatment is the implantation of flow-diverters (FD). Methods to predict their treatment success before or directly after implantation are not well investigated yet.

Experimental and CFD flow studies in an intracranial aneurysm model with Newtonian and non-Newtonian fluids.

Background: According to the clinical data, flow conditions play a major role in the genesis of intracranial aneurysms. The disorder of the flow structure is the cause of damage of the inner layer of the vessel wall, which leads to the development of cerebral aneurysms. Knowledge of the alteration of the flow field in the aneurysm region is important for treatment.

Evaluation of intra-aneurysmal hemodynamics after flow diverter placement in a patient-specific aneurysm model.

Background: The growth and rupture of cerebral aneurysms is intrinsically related to the hemodynamics prevailing in the diseased area. Therefore, a better understanding of intra-aneurysmal hemodynamics is essential for developing effective treatment methods.

Objective: The intention of this study was to evaluate the intra-aneurysmal flow and flow reduction induced by flow diverters in a true-to-scale elastic aneurysm model, obtained from real patient data.

Opened end-to-side technique for end-to-side anastomosis and analyses by an elastic true-to-scale silicone rubber model.

The end-to-side anastomosis is frequently used in microvascular free flap transfer, but detailed rheological analyses are not available. The purpose of this study was to introduce a new modified end-to-side (Opened End-to-Side, OES-) technique and compare the resulting flow pattern to a conventional technique. The new technique was based on a bi-triangulated preparation of the branching-vessel end, resulting in a "fish-mouthed" opening.

Flow analyses of microvascular bifurcation using laser Doppler anemometry.

Introduction: Vascular surgery affects, among other factors, vessel geometry and might result in significant flow changes. For this reason a basic understanding of flow behavior at bifurcations plays an important role for microsurgeons. The aim of the present work was to establish an experimental model that enables rheological analyses of microvascular techniques.

Coronary stents cause high velocity fluctuation with a flow acceleration and flow reduction in jailed branches: an in vitro study using laser-Doppler anemometry.

Flow disturbance and reduced blood flow have been associated with higher restenosis rates and clinical adverse events after coronary interventions. In the present study, we sought to investigate flow alterations that occurred after stent implantation in a coronary model, within and adjacent to the stented segment. Two stents (Carbostent, Tetrastent) with different strut design were deployed in the left anterior descending artery (LAD) of a 1:1 scaled silicon coronary model.

[Novel uses of afterbirth tissues in regenerative medicine].

Introduction: Afterbirth tissues, which include the umbilical cord, placenta, amnion, and cord blood, are usually discarded. Recent progress in regenerative medicine suggests that we re-evaluate these tissues and assess their therapeutic potential.

Methods: Firstly the unique properties of afterbirth tissues and their current use in regenerative medicine are summarised.

The effect of stents on intra-aneurysmal hemodynamics: in vitro evaluation of a pulsatile sidewall aneurysm using laser Doppler anemometry.

Introduction: Hemodynamic modification by means of flow diversion is increasingly used for treatment of intracranial aneurysms. Despite of promising results, there is still a paucity of methods to reliably predict long-term success of this technique. Laser Doppler anemometry (LDA) can be used to quantify the influence of stents on intra-aneurysmal flow in vitro.

Fluidodynamic evaluation of arteriovenous fistulae for hemodialysis.

Arteriovenous fistulae (AVF) are commonly used in dialysis treatment of uremic patients. However, many AVF create problems and have to be re-examined. Problems arise in the cannulation site and must be treated with antibiotics, and stenosis, both in the arterial and in the venous side of the AVF.

Biofluid mechanics--an interdisciplinary research area of the future.

Biofluid mechanics is a complex field that focuses on blood flow and the circulation. Clinical applications include bypass and anastomosis surgery, and the development of artificial heart valves and vessels, stents, vein and dialysis shunts. Biofluid mechanics is also involved in diagnostic and therapeutic measures, including CT and MRI, and ultrasound.

Theoretical approach to blood ejection from the human left ventricle.

An ejection dynamics mathematical model of human left ventricle (LV) based on physiological data of human heart is proposed in this study. The mathematical equations were expressed in terms of vorticity-stream function equations in a prolate spheroidal coordinate system. These equations combined with specified boundary conditions were numerically solved by using an alternating-direction-implicit (ADI) algorithm with second order accuracy.

Do contrast agents affect ultrasound flow measurements?

The use of iodine contrast agents during angiography can put patients at risk. The replacement of angiography through duplex ultrasound methods would, therefore, be of great interest. Even when duplex sonography is used however, an x-ray angiography is often performed afterwards to verify the diagnosis.

Flow velocities after carotid artery stenting: impact of stent design. A fluid dynamics study in a carotid artery model with laser Doppler anemometry.

Purpose: To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model.

Methods: Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract.

Localization of bypass-induced changes in flow in coronary artery models.

Right coronary artery bypass restores blood flow through heart tissues. This also induces changes in flow leading to its failure. By this work the sites which are prone to such changes are localized.

Changes in carotid artery flow velocities after stent implantation: a fluid dynamics study with laser Doppler anemometry.

Purpose: To study the influence of stent size and location on flow patterns in a physiological carotid model.

Methods: Wallstents were positioned in silicon models of the carotid artery at various locations: 2 stents appropriately sized to the anatomy were placed in (1) the internal carotid artery (ICA) and (2) the ICA extending completely into the common carotid artery so as to cover the external carotid artery (ECA) orifice. Another 2 stents were placed in the ICA extending (1) partially and (2) completely into the bulb to simulate stent displacement and disproportion between stent size and the original vessel geometry.

Experimental flow studies in an elastic Y-model.

To determine the causes and history of atherosclerosis it is necessary to understand the hemodynamic parameters of blood circulation. Hemodynamic parameters play an important role in the formation of atherosclerotic plaques, especially near bends and bifurcations where the flow separates from the wall. Here the flow is laminar and non-axial with eddies, secondary flow, flow separation and stagnation points.

On using experimentally estimated wall shear stresses to validate numerically predicted results.

The objective of this investigation was to assess the use of experimentally estimated wall shear stresses to validate numerically predicted results. The most commonly cited haemodynamic factor implicated in the disease initiation and proliferation processes at graft/artery junctions is wall shear stress (WSS). WSS can be determined from the product of the viscosity of the fluid and the wall shear rate.

The discrimination of stenosed carotid bifurcation models with smooth and irregular plaque surface. Part II. The multivariate statistical analysis of ultrasonic Doppler velocity data.

According to the conclusion of the first part of the paper the Doppler spectral indices were analyzed in a detailed manner to provide a means to differentiate bifurcation models with different irregularities. Autoregressive (AR) models using the Akaike FPE criterion were fitted to the curves of the spectral broadening index, turbulence intensity index and coefficient of symmetry. These curves were also submitted to the data reduction significant point extraction algorithm.

The discrimination of stenosed carotid bifurcation models with smooth and irregular plaque surface. Part I. Laser and ultrasonic Doppler flow studies.

Irregular carotid lesion surface is considered as a factor increasing the risk of the cerebral embolism. The objective of the study was to investigate the possibility to distinguish models of stenosed carotid bifurcation with lesion irregularity on the basis of the properties of flow velocity distributions. Two groups of elastic replicas of carotid bifurcations with different stenosis degree were investigated.

An introduction to biofluid mechanics--basic models and applications.

Cardiovascular disease is the primary cause of morbidity and mortality in the western world. Complex hemodynamics play a critical role in the development of atherosclerosis and the processes of aging, as well as many other disease processes. Biofluid mechanics play a major role in the cardiovascular system and it is important to understand the forces and movement of blood cells and whole blood as well as the interaction between blood cells and the vessel wall.

Laser-Doppler-anemometry studies of flow behavior in rigid and elastic varicose vein models.

Flow behavior and velocity were studied in six varicose vein models with simulated arteriovenous anastomoses (AVAs). Experiments were performed to determine whether incoming flow entering from AV-anastomoses or small feeder veins could create either small jet streams or velocity fluctuation, which might then cause veins to bulge and get tortuous. Flow was analyzed in areas of flow change.

Flow Characteristics in an Anatomically Realistic Compliant Carotid Artery Bifurcation Model.

A numerical model for the pulsatile blood flow in an anatomically realistic compliant model of the human carotid artery bifurcation has been developed. The geometric model has been generated on the basis of an optically digitized arterial cast. The effects of the geometrically realistic flow domain and of the wall distensibility on the flow characteristics are investigated.