2D Computational Fluid Dynamic Modeling of Human Ventricle System Based on Fluid-Solid Interaction and Pulsatile Flow.

Many diseases are related to cerebrospinal fluid (CSF) hydrodynamics. Therefore, understanding the hydrodynamics of CSF flow and intracranial pressure is helpful for obtaining deeper knowledge of pathological processes and providing better treatments. Furthermore, engineering a reliable computational method is promising approach for fabricating in vitro models which is essential for inventing generic medicines. A Fluid-Solid Interaction (FSI)model was constructed to simulate CSF flow. An important problem in modeling the CSF flow is the diastolic back flow. In this article, using both rigid and flexible conditions for ventricular system allowed us to evaluate the effect of surrounding brain tissue. Our model assumed an elastic wall for the ventricles and a pulsatile CSF input as its boundary conditions. A comparison of the results and the experimental data was done. The flexible model gave better results because it could reproduce the diastolic back flow mentioned in clinical research studies. The previous rigid models have ignored the brain parenchyma interaction with CSF and so had not reported the back flow during the diastolic time. In this computational fluid dynamic (CFD) analysis, the CSF pressure and flow velocity in different areas were concordant with the experimental data.

Flow simulation of a diaphragm-type ventricular assist device with structural interactions.

A numerical simulation of the fluid and structure interactions was performed for a diaphragm-type Ventricular Assist Device (VAD). The simulation was included two incompressible fluids and three elastic solid regions. The detailed information of both fluid and solid dynamic are crucial to evaluate the performance of the device. Localization of potential points prone to hemolysis and thrombus formation and disturbed flow with creation of recirculation zones are vary important. Here, the HeartSaver VAD was modeled as a two dimensional chambers with an inlet and an outlet elastic valves, an elastic sac-shape membrane, driving fluid and blood. A pulsatile velocity condition was applied at the inlet of the driving fluid chamber. As the results, the flow characteristics affecting the blood cells including velocity, pressure, wall shear stress and the elastic valves operation were presented in details.

An evaluation of a combined spline based and rate of energy dissipation based segmentation of medical blood flow images.

Domain characteristics provide some constraints for accurate segmentation of special domain (e.g. flow) images. These constraints usually obtain a type of region based segmentation and in combination with the intensity based segmentation methods obtain overcoming results. When a boundary based segmentation method is considering to be aligned with these region based methods, some special efforts are necessary to make them compatible. Here we address a method to combine two boundary and regional based segmentation methods. In this regard boundary based segmentation is changed to be compatible with a regional based energy dissipation constraint in a sample flow domain. A quadratic spline function is used for boundary based segmentation of flow domain. The regional equivalent factor of this method is provided using the Gauss theorem. The numerical implementation of this method is provided with construction of boundary elements on the spline boundary segments. The rate of energy dissipation at blood elements is applied as the regional segmentation factor. It calculated from the velocity data of the flow Image. An overcoming segmentation factor is provided by mixing both methods. For implementation of this method a simulated Phase- Contrast Magnetic Resonance Image (PC-MRI) of Couette flow system is considered.