Fixation of a human rib by an intramedullary telescoping splint anchored by bone cement

A novel concept for rib fixation is presented that involves the use of a bioresorbable polymer intramedullary telescoping splint. Bone cement is used to anchor each end of the splint inside the medullary canal on each side of the fracture site. In this manner, rib fixation is achieved without fixation device protrusion from the rib, making the splint completely intramedullary. Finite element analysis is used to demonstrate that such a splint/cement composite can preserve rib fixation subjected to cough-intensity force loadings. Computational fluid dynamics and porcine rib experiments were used to study the anchor formation process required to complete the fixation

Formation dynamics of ultrasound contrast agent materials

Abstract not available

Development of optimized vascular fractal tree models using level set distance function

Using the concepts of fractal scaling and constrained constructive optimization (CCO), a branching tree model, which has physiologically meaningful geometric properties, can be constructed [12-14]. A vascular branching tree model created in this way, although statistically correct in representing the vascular physiology, still does not possess a physiological correct arrangement of the major arteries. A distance-function based technique for 'staged growth' of vascular models has been developed in this work to address this issue. Time-dependent constraints based on a signed-distance level set function have been added, so that the tree models will first be grown near the designated surface(s) and, then, gradually allowed to penetrate into the enclosed volume. The proposed technique has been applied to construct a model of the human cerebral vasculature, which is characterized by the above-mentioned distribution of the arteries

Dynamics of pulsatile flow in fractal models of vascular branching networks

Efficient regulation of blood flow is critically important to the normal function of many organs, especially the brain. To investigate the circulation of blood in complex, multi-branching vascular networks, a computer model consisting of a virtual fractal model of the vasculature and a mathematical model describing the transport of blood has been developed. Although limited by some constraints, in particular, the use of simplistic, uniformly distributed model for cerebral vasculature and the omission of anastomosis, the proposed computer model was found to provide insights into blood circulation in the cerebral vascular branching network plus the physiological and pathological factors which may affect its functionality. The numerical study conducted on a model of the middle cerebral artery region signified the important effects of vessel compliance, blood viscosity variation as a function of the blood hematocrit, and flow velocity profile on the distributions of flow and pressure in the vascular network

Dynamics of pulsatile flow in a fractal model of the cerebral microvascular system

Abstract not available

Synthesis of ultrasound contrast agent materials

Abstract not available

Modeling of flow through the circle of Willis and cerebral vasculature to assess the effects of changes in the peripheral small cerebral vasculature on the inflows

The cerebral hemodynamics through the circle of Willis (CoW) was modeled by coupling a three-dimensional (3D) Computational Fluid Dynamics (CFD) model of the CoW with a one-dimensional (1D) branching tree model of the peripheral cerebral vasculature. CFD was used to model the 3D transient flow through idealized and patient-specific CoW geometries. A 1D pipe network model was also used to predict the flow through the idealized CoW. The coupled model provided useful insight into the variation of the flow through the CoW as a result of possible physiological and pathological changes (for example associated with ‘onset’ of Alzheimer’s Disease) in the peripheral networks of small cerebral vasculature. A comparison was made between the complete CoW and geometric variations with communicating arteries missing. A CoW inflow ratio showed that vasoconstriction of the peripheral vasculature of the posterior cerebral artery predominantly decreases the flow rate in the vertebral arteries, while vasoconstriction of the peripheral vasculature of the anterior and middle cerebral arteries predominantly decreases the flow rate of the internal carotid arteries. These changes in inflow in arteries that are easily monitored may be used to determine if there is vasoconstriction of the peripheral small cerebral vasculature which may indicate diseased states

Modeling of flow through the circle of Willis and cerebral vasculature to assess the effects of changes in the peripheral small cerebral vasculature on the inflows

The cerebral hemodynamics through the circle of Willis (CoW) was modeled by coupling a three-dimensional (3D) Computational Fluid Dynamics (CFD) model of the CoW with a one-dimensional (1D) branching tree model of the peripheral cerebral vasculature. CFD was used to model the 3D transient flow through idealized and patient-specific CoW geometries. A 1D pipe network model was also used to predict the flow through the idealized CoW. The coupled model provided useful insight into the variation of the flow through the CoW as a result of possible physiological and pathological changes (for example associated with ‘onset’ of Alzheimer’s Disease) in the peripheral networks of small cerebral vasculature. A comparison was made between the complete CoW and geometric variations with communicating arteries missing. A CoW inflow ratio showed that vasoconstriction of the peripheral vasculature of the posterior cerebral artery predominantly decreases the flow rate in the vertebral arteries, while vasoconstriction of the peripheral vasculature of the anterior and middle cerebral arteries predominantly decreases the flow rate of the internal carotid arteries. These changes in inflow in arteries that are easily monitored may be used to determine if there is vasoconstriction of the peripheral small cerebral vasculature which may indicate diseased states