Modeling pulsatile flow past heart valves remains a relatively unexplored but critical area. Due to the geometric complexity and the interaction between the flowing blood and the heart valve leaflets, existing numerical techniques that require domain discretization, such as finite element methods or finite difference techniques, cannot fully represent the moving and deforming boundaries present in an operating valve. Our aim is to develop a technique to model the flow through heart valves which includes the interaction between the blood flow and the valve leaflets using the radial functions method (RFM). The RFM is a meshless technique that fully accounts for moving and deforming surfaces and thus is well suited to model the blood flow and its interaction with leaflet motion. Here we present a 2D fluid structure interaction (FSI) model of the blood flow through a bileaflet mechanical heart valve (MHV).

Cerebral aneurysms are a mayor cause of hemorrhagic stroke which is a highly significant and devastating disease. Currently there is an increased interest in using endovascular devices for flow diversion such as stents, for treating intracranial aneurysms [1]. Several studies have proven that the geometry and position of the stent in its deployed state play a mayor role in the way the blood flow is diverted. The design of flow diverters and the selection of the most appropriate device for a given aneurysm require a computational model to study the changes in the blood flow patterns after stenting. In this paper an innovative methodology for virtual deployment of stents within patient-specific anatomical models is presented. One remarkable property of this technique is the ability to easily interchange different stent designs within the same model in order to perform fast comparative characterizations.

High Intensity Focused Ultrasound (HIFU) shows considerable promise as a minimally-invasive technique for tumor ablation. A typical HIFU procedure involves focusing of acoustic energy in a small region, with the absorbed acoustic energy causing localized rise in tissue temperature. Temperature rise of the order of 40–60°C is achieved within seconds, causing immediate cell necrosis in the targeted region.

Remodeling plays an important role in normal arterial physiology and in the genesis and progression of vascular pathologies. Arteries respond to changes in their global mechanical environment, characterized by blood flow rate, arterial pressure, and longitudinal stretch by changing geometry, structure and composition. Remodeling results from altered vascular cell activity caused by perturbed local stresses and strains and, in general, tends to restore the local mechanical parameters to their baseline values. To date, experimental investigations in vivo and in organ culture have focused on remodeling responses initiated by controlled sustained changes in one global mechanical parameter while keeping the others at baseline values.

Invasive measurement of pulmonary vascular flow and pressure provides the hemodynamic status of the pulmonary circulation for children with pulmonary arterial hypertension (PAH). Clinicians are primarily interested in pulmonary vascular resistance, which is the mean pressure of the circuit divided by the mean flow through it [1], in that it is believed to well-quantify the right ventricular (RV) afterload, the primary determinant of mortality. However, previous and current investigations on the pulmonary vascular stiffness (PVS), input impedance and RV power [2–4] have found PVS to be an important contributor to power, and thus, afterload. These previous and current investigations focus on the analysis of clinical data, which is limited by the clinical equipment and techniques.

The architecture of the vascular wall is highly intricate and requires unique biomechanical properties in order to function properly. Native artery is composed of a mix of collagens, elastin, endothelial cells (ECs), smooth muscle cells (SMC), fibroblasts, and proteoglycans arranged into three distinct layers: the intima, media, and adventitia. Throughout artery, collagen and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery while undergoing pulsatile deformations [1]. The low-strain mechanical response of artery to blood flow is dominated by the elastic behavior, of elastin, which prevents pulsatile energy from being dissipated as heat [2]. A higher amount of energy loss indicates a decrease in recoverability, which could lead to eventual disruption of blood flow. An effective way to quantify recoverability is through hysteresis and compliance measurement. The hypothesis of this study was that the fabrication of a multi-layered electrospun tissue engineering scaffold composed of polycaprolactone (PCL), elastin, and collagen would demonstrate dynamic mechanical properties indicative of a highly elastic material, similar to the three distinct layers of native arterial tissue, while remaining conducive to tissue regeneration. PCL was chosen, in this case, to provide mechanical integrity and elasticity, while elastin and collagen would provide further elasticity and bioactivity [3,4].

In the past, various techniques such as indicator dilution, transit time, parametric imaging, or first-pass distribution have been used to estimate blood flow rates during angiographic contrast injections. We have previously employed the method of modeling contrast concentration curves to assess changes in flow exchange between parent cerebral vessels and cerebral aneurysms due to endovascular treatment by flow divertors [1]. There has been concern, however, that contrast injected under such situations may remain as a separate slug or stream flowing with blood or that contrast may settle from blood in the direction of gravity due to its higher density [2,3]. According to this argument, therefore, the analysis of the transport of angiographic contrast visualized under X-ray cannot be used to represent the transport of blood.

Cerebral aneurysms are widely believed to form and grow as a result of the interactions of hemodynamics and wall mechano-biology. Researchers have used a variety of tools to study these complex multi-factorial mechanisms including animal, in vitro , and computational models. The goal of these experiments has been to approximate the in vivo environment so that theories about the natural history of brain aneurysms can be developed and tested in realistic systems. Studying the link between hemodynamics and clinical observations of aneurysm progression is necessary to reach an understanding of the relative importance of the different mechanisms involved in these processes [1]. The objective of our research is to investigate the possible relationship between wall shear stress (WSS) — which is known to regulate mechano-biological processes at the arterial wall — produced by different blood flow patterns and the evolution and rupture of cerebral aneurysms.

Coronary circulation is mainly regulated by two serial resistances, namely, epicardial stenosis and microvascular impairments, both causing abnormal coronary blood circulation [1]. Delineation of the true severities of these diseases is important to guide clinical decision-making processes for the selection of appropriate treatment procedures [2]. The presently used diagnostic parameters: FFR (fractional flow reserve defined as the ratio of distal to proximal hyperemic pressure) and CFR (coronary flow reserve defined as ratio of basal to hyperemic flow) [1], for the evaluation of severity of epicardial coronary stenosis are well established in clinical practice. On the other hand, current methods to evaluate the microcirculatory status are limited [3].

Much research has been conducted to obtain detailed and accurate information of blood flow field for clarification and advanced diagnosis of circulatory diseases. In order to reproduce complicated real flow field, we have proposed the concept of integration of measurement and computation, and developed the ultrasonic-measurement-integrated (UMI) simulation [1, 2]. In this study, we propose MR-measurement-integrated (MR-MI) simulation by applying the methodology to the MR (Magnetic Resonance) measurement. In the MR-MI simulation, the difference between the computational result and the PC MRI (Phase-Contrast Magnetic Resonance Imaging) measurement data of the three-dimensional velocity vector field is fed back to the numerical simulation (see Fig. 1). The objective in this study is to investigate the characteristics of MR-MI simulation by numerical experiment dealing with a model steady blood flow field in a cerebral aneurysm.

Ventricular assist devices (VADs) have received widespread application to treat adults with end-stage heart failure. However, application to the pediatric population has been limited due to the excessive size; and therefore miniature, pediatric VADs (PVADs) are now being developed for the pediatric population to expand the current treatment options available to young patients with congenital heart defects and acquired heart disease. These pumps are typically connected via the left ventricular apex (via an inflow cannula) to the ascending aorta (via an outflow cannula). The distal anastomosis between outflow cannula and aorta has been studied by other researchers [1, 2] revealing complex fluid dynamic phenomena due to the non-physiologic confluence of native blood flow and outflow from the VAD. The corresponding pediatric anastomosis differs in dimensions and proportions to the adult, and has not yet been studied. The objective of this initial study is to examine the influence of cannula design, location, angle of insertion, and flow rate on the macro- and micro-fluid dynamics in the pediatric aorta. This parametric study is intended to provide both developers and surgeons with insight that would lead to optimization of both the cannula and surgical procedure, with particular emphasis at avoiding recirculation and stagnation flows commonly associated with platelet activation and thrombus generation [2, 3].

A highly resolved 3D geometry of a bileflet mechanical heart valve (MHV) was constructed to study the contribution of the forward and regurgitant flow phases to platelet damage. Platelet stress accumulation during repetitive passages past the valve was calculated using a damage accumulation model in pertinent trajectories. Additionally a discrete particles dynamics (DPD) multiscale modeling approach, which widely departs from the traditional continuum approach, was applied to this MHV geometry. It generated viscous blood flow velocity distributions, and is envisioned to further facilitate multiscale simulations of flow induced thrombogenicity in blood recirculating devices.

This paper describes development of the prediction method of thrombus formation by Computational Fluid Dynamics (CFD) on pipe orifice shear flows. These shear flows are typical models of the flow in the rotary blood pump. In this investigation, the thrombus formation in blood plasma flow is visualized, and modified lattice Boltzmann method are used to predict the backward forwarding step flow, that is simple model of the orifice flow.

Vascular applications in regenerative medicine include blood vessel substitutes and vasculogenesis in ischemic or engineered tissues. For these repair processes to be successful, there is a need for a stable supply of endothelial and smooth muscle cells. For blood vessel substitutes, the immediate goal is to enable blood flow, but vasoactivity is necessary for long term success. In engineered vessels, it is thought that endothelial cells will serve as an anti-thrombogenic lumenal layer, while smooth muscle cells contribute to vessel contractility. In other clinical applications, what is needed is not a vessel substitute but the promotion of new vessel formation (vasculogenesis). A simplified account of vasculogenesis is that endothelial cells assemble to form vessel-like structures that can then be stabilized by smooth muscle cells. Overall, the need for new vasculature to transfer oxygen and nutrients is important to reperfuse not only ischemic tissue in vivo , but also dense, structurally complex engineered tissue. The impact of these vascular therapies, however, is limited in part by the low yield and inadequate in vitro proliferation potential of primary endothelial and smooth muscle cells. Thus, there is a need to address the cell sourcing issue for vascular cell-based therapies, potentially using stem cells.

In 1948, Pennes [1] presented a mathematical model of heat transfer in human tissue. The effect of blood flow on heat transfer was modeled as heat sink or source whose magnitude is proportional to the volumetric perfusion rate and difference between arterial and venous temperature [2]. Pennes assumed that thermal equilibrium occurs in the capillary beds, although Chen [3] showed that it occurs in bigger vessels before the blood enters the beds. Weinbaum et al. [2] and Zhu et al. [4] studied the thermal effect of vessels in the range of 50 to 1,000 μm on muscle tissue, and recognized the importance of countercurrent heat exchange. Hirata et al. [5] showed that the heat loss in the forearm is enhanced by the venous blood returning through the superficial veins and that arterious-venous anastomoses (AVAs) presented in the hands are important to thermoregulation.

Stenting is the most commonly used medical procedure to restore blood flow in stenotic arteries. During this endovascular intervention, a small tube-like structure is implanted in the narrowed section of the diseased artery. The vast majority of stents are crimped (i.e. plastically deformed) on a folded balloon (balloon expandable stents). After insertion through a small incision in the femoral or radial artery using a catheter, the balloon is inflated and the stent deploys. Following to the expansion, the balloon is deflated and retracted and from then on, the stent acts as a mechanical scaffold for the enlarged lumen.

Today cardiac complications are the leading cause of death in the developed world [1]. Millions of people suffer from cardiovascular disease, with most of the cases caused by or related to atherosclerosis. Historically, blood flow in stenosed arteries has been restored by means of balloon angioplasty. In 1987 stents were introduced to the procedure in order to provide structural support to the diseased artery.

An MR thermometry technique with sub-degree celsius accuracy is needed to measure in vivo temperatures vs. time in porcine brains at ultra-high fields. Porcine models are used to study thermoregulatory temperature response of the ultra-high field radiofrequency (RF) heating. The porcine hot critical temperature limit is comparable to and lower than that of humans. Also, porcine thermoregulatory mechanisms are similar to humans. Thus, conservative porcine thermoregulatory temperature responses can help develop new RF safety thresholds for ultra-high field human MRI. Sub-degree C temperature accuracy is needed since RF safety guidelines limit the maximum in vivo head temperature change due to RF heating to 1 °C over the core body temperature. Three-dimensional temperature maps over time are required since non-uniform RF power deposition at ultra-high fields and blood flow produce non-uniform in vivo temperatures with local hot spots. Thermogenic hazards are related to in vivo temperatures and temperature-time history — and not to the typically measured whole head average specific absorption rate.

The blood circulation system plays an important role inside human body. It connects all the tissues and organs, transports nutrition to cells and takes away the waste so that the vivo circumstance of cells inside human body is maintained. In specific, it is through the microcirculation system of blood flow in capillaries that the mass and energy transfer between the blood and tissues are achieved.

Non-uniform extravasation from blood vessels, elevated interstitial fluid pressure (IFP), and transport by bulk fluid motion in the extracellular space have all been determined to contribute to the non-uniform tissue distribution of systemically delivered agents in solid tumors. The aforementioned factors can lead to inadequate and uneven uptake in tumor tissue which has been shown to be a major obstacle to macromolecules in clinical cancer therapy [1]. Recently developed computational tumor models have described blood flow either in a single vessel or capillary network with variations in space and time [2]. These studies do not account for heterogeneous tissue transport properties in regions of leakier vessels [3].