Geometrical Models of Vertebral Arteries and Numerical Simulations of the Blood Flow Through Them

2008 ◽  
Author(s):  
Krzysztof Jozwik ◽  
Damian Obidowski
Keyword(s):  
Blood Flow ◽  
Numerical Simulations ◽  
Blood Vessels ◽  
Human Body ◽  
Special Kind ◽  
3D Models ◽  
Vertebral Arteries ◽  
The Individual ◽  
Physical Phenomena ◽  
The Brain

Vertebral arteries are a system of two blood vessels through which blood is carried to the rear region of the brain. This region of the human body has to be very well supplied with blood, without any breaks or deficiencies in the blood flow. Blood is delivered to the brain through carotid arteries as well. All these arteries are connected to the circle of Willis, which has to fulfill all demands of the human brain as far as the blood flow is concerned. However, vertebral arteries due to their position and shape are a special kind of blood vessels. They originate at various distances from the aortic ostium, may branch off at different angles, have various length, inner diameter and spatial shape. Three different geometries of vertebral arteries, which most frequently occur in the human body structure, have been chosen, and for each twenty five various combinations of artery inner diameters have been used to generate 3D models of these arteries. For seventy five different models thus created, the numerical simulations have been performed. The results obtained have indicated explicitly that differences in the flow and instantaneous velocity values in vertebral arteries and in the point they join to form the basilar artery do not result from pathological changes in the artery system, but may follow from physical phenomena that occur in arteries as a consequence of the pulsating character of the flow and the unique geometry, which is related to the individual human anatomical structure.

Fit Vs Faint: Assessing Work Causation in “Idiopathic Fall” Cases

2014 ◽  
Vol 19 (5) ◽  
pp. 3-12
Author(s):  
Lorne Direnfeld ◽  
David B. Torrey ◽  
Jim Black ◽  
LuAnn Haley ◽  
Christopher R. Brigham
Keyword(s):  
Blood Flow ◽  
Electrical Activity ◽  
Loss Of Consciousness ◽  
Brain Electrical Activity ◽  
Medical Terminology ◽  
Scientific Analysis ◽  
Medical Causation ◽  
The Individual ◽  
The Brain ◽  
Current Science

Abstract When an individual falls due to a nonwork-related episode of dizziness, hits their head and sustains injury, do workers’ compensation laws consider such injuries to be compensable? Bearing in mind that each state makes its own laws, the answer depends on what caused the loss of consciousness, and the second asks specifically what happened in the fall that caused the injury? The first question speaks to medical causation, which applies scientific analysis to determine the cause of the problem. The second question addresses legal causation: Under what factual circumstances are injuries of this type potentially covered under the law? Much nuance attends this analysis. The authors discuss idiopathic falls, which in this context means “unique to the individual” as opposed to “of unknown cause,” which is the familiar medical terminology. The article presents three detailed case studies that describe falls that had their genesis in episodes of loss of consciousness, followed by analyses by lawyer or judge authors who address the issue of compensability, including three scenarios from Arizona, California, and Pennsylvania. A medical (scientific) analysis must be thorough and must determine the facts regarding the fall and what occurred: Was the fall due to a fit (eg, a seizure with loss of consciousness attributable to anormal brain electrical activity) or a faint (eg, loss of consciousness attributable to a decrease in blood flow to the brain? The evaluator should be able to fully explain the basis for the conclusions, including references to current science.

Microfluidics of blood in blood vessels stenosis

2016 ◽  
Vol 11 (2) ◽  
pp. 210-217 ◽  
Author(s):  
A.T. Akhmetov ◽  
A.A. Valiev ◽  
A.A. Rakhimov ◽  
S.P. Sametov ◽  
R.R. Habibullina
Keyword(s):  
Blood Flow ◽  
Blood Vessels ◽  
Hydraulic Resistance ◽  
Microfluidic Device ◽  
Human Body ◽  
Vascular System ◽  
Hydrodynamic Conditions ◽  
Microstructure Change ◽  
Healthy Part

It is mentioned in the paper that hydrodynamic conditions of a flow in blood vessels with the stenosis are abnormal in relation to the total hemodynamic conditions of blood flow in a vascular system of a human body. A microfluidic device developed with a stepped narrowing for studying of the blood flow at abnormal conditions allowed to reveal blood structure in microchannels simulating the stenosis. Microstructure change is observed during the flow of both native and diluted blood through the narrowing. The study of hemorheological properties allowed us to determine an increasing contribution of the hydraulic resistance of the healthy part of the vessel during the stenosis formation.

Collective methods of propulsion and steering for untethered microscale nanorobots navigating in the human vascular network

2010 ◽  
Vol 224 (7) ◽  
pp. 1505-1513 ◽  
Author(s):  
S Martel
Keyword(s):  
Blood Flow ◽  
Blood Vessels ◽  
Human Body ◽  
Interventional Procedures ◽  
Vascular Network ◽  
Single Type ◽  
Tumour Targeting ◽  
Miniature Robots ◽  
Medical Diagnostic ◽  
Blood Flow Velocities

In the field of medical nanorobotics, nanometre-scale components and phenomena are exploited within the context of robotics to provide new medical diagnostic and interventional procedures, or at least to enhance the existing ones. The best route for such miniature robots to access various regions inside the human body is certainly the vascular network. Such a network is made of nearly 100 000 km of blood vessels varying in diameters from a few millimetres in the arteries down to ∼ 4 μm in the capillaries with respective important variations in blood flow velocities. When injected in the blood circulatory network using existing modern techniques such as catheterization, such robots must travel from larger-diameter vessels before reaching much tinier capillaries. As such, the use of a single type of microscale robots capable of travelling in various environments and conditions related to such different blood vessels while being trackable by an external system seems, at the present time, inconceivable. Therefore, as explained in this article, an approach based on the use of several types of microscale robots with complementary methods of propulsion and steering capable of operating in a collective manner is more likely to achieve better results. This is especially true for interventions such as direct tumour targeting where the tiniest blood vessels such as the ones found in the angiogenesis network must be travelled.

119 Visualization of Vascular Structures of the Brain Through a Novel Multispectral Fluorescence Microscope After Intravenous Application of ICG

Neurosurgery ◽  
2017 ◽  
Vol 64 (CN_suppl_1) ◽  
pp. 226-226
Author(s):  
Dimitrios Athanasopoulos
Keyword(s):  
Blood Flow ◽  
Blood Vessels ◽  
Intravenous Injection ◽  
White Light ◽  
Surgical Microscope ◽  
Light Image ◽  
Fluorescent Image ◽  
Surgical Clip ◽  
Vascular Structures ◽  
The Brain

Abstract INTRODUCTION Vascular structures are intraoperatively visualized through the eye-piece of a surgical microscope. The blood flow within the blood vessels can be demonstrated via indocyanine green (ICG) fluorescence. In this study we wanted to find out whether the development of a novel fluorescent surgical microscope, overlapping a multispectral fluorescent image on a white light image, is superior, equal or inferior, compared to the previous models. Moreover, it shall be proved, whether multispectral fluorescence enhances surgeon's orientation through the precise and clearer visualization of blood vessels and the blood flow. METHODS A total of 8 porcine animal models were used. After fixation of the animal's head the parietal cortex and the cortical blood vessels were exposed. A digital imaging of the arterial perfusion, capillary transition and venous drainage after intravenous injection of ICG (5 ml; 5 mg/ml) was then performed. The blood flow was artificially blocked by a surgical clip. After repetitive intravenous injection of ICG and visualisation with multispectral view, the surgical clip was removed and the reperfusion of the brain tissue was visualized with the real time ICG perfusion. RESULTS >The visualization of the anatomical structures of the surgical field under white light as well as the image overlapping were easily performed. The occlusion of blood vessels with surgical clips demonstrate a blockage of the ICG perfusion on the multispectral fluorescent image. The ICG perfusion was again demonstrated after removing the surgical clip and reperfusion of the blood vessel. CONCLUSION Multispectral fluorescence was shown to be superior to the classic ICG fluorescence. With the development of a novel multispectral surgical microscope, which overlaps a fluorescent image on a white light image, the data delivered to the surgeon are enhanced, compared to the previous models. Moreover, the surgeons's orientation is improved thanks to the clear visualization of blood vessels and the blood flow.

Effects of hematocrit variations on regional hemodynamics and oxygen transport in the dog

1980 ◽  
Vol 238 (4) ◽  
pp. H545-H522 ◽  
Author(s):  
F. C. Fan ◽  
R. Y. Chen ◽  
G. B. Schuessler ◽  
S. Chien
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Blood Vessels ◽  
Oxygen Transport ◽  
Oxygen Supply ◽  
Blood Flows ◽  
Regional Hemodynamics ◽  
Regional Blood Flows ◽  
Splenic Vessels ◽  
The Brain

The responses of alterations in regional hemodynamics and oxygen transport rate to hematocrit (Hct) were studied in 20 pentobarbitalized dogs. Hemodilution was carried out by isovolemic exchange with plasma in 12 dogs and the hemoconcentration with packed cells in 8 dogs. The cardiac output and regional blood flows were determined with the microsphere technique. In hemodilution, the increases of blood flow to the myocardium and the brain were out of proportion to the increase of cardiac output; the oxygen supply to the myocardium remained unchanged while that to the brain decreased only slightly. In hemoconcentration, vasodilation occurred in the myocardium and the brain to maintain constant oxygen supply. Splenic vessels had marked vasoconstriction with Hct alteration in either direction. Blood vessels in the liver, intestine, and kidney responded with a milder vasoconstriction and maintained a constant oxygen supply between Hct of 30-55%. Therefore, during Hct alteration, redistribution of blood flow to myocardium and brain occurred. The optimal Hct range for constant oxygen supply was different among various organs.

scholarly journals Treatment of Vasculitis: Beyond the Basics

2020 ◽  
Author(s):  
Muhammad Ishaq Ghauri ◽  
Muhammad Shariq Mukarram
Keyword(s):  
Blood Flow ◽  
Mycophenolate Mofetil ◽  
Blood Vessels ◽  
Human Body ◽  
Systemic Vasculitis ◽  
Organ Damage ◽  
Biological Agents ◽  
Cytotoxic Agents ◽  
Is Failure ◽  
Primary Vasculitis

Vasculitis is the inflammation of blood vessels in the human body. It causes changes and remodeling in the walls of the vessels that include thickening, narrowing and scarring. As a result, the blood flow to the organs and tissues gets restricted leading to organ damage. The cause of primary vasculitis is not known; however, most cases are thought to be autoimmune. In the present era, it is getting difficult to treat vasculitis with conventional therapies, which includes cyclophosphamide, methotrexate, azathioprine and mycophenolate mofetil, with increasing rates of relapses. Since ever, corticosteroids and cytotoxic agents or immunosuppressants have been the mainstay for treating systemic vasculitis. However, the introduction of newer biological agents have bring about a revolution in the treatment of relapses and in cases where there is failure to induce and sustain remission.

The Neurovascular Unit: Focus on the Regulation of Arterial Smooth Muscle Cells

2020 ◽  
Vol 16 (5) ◽  
pp. 502-515 ◽  
Author(s):  
Patrícia Quelhas ◽  
Graça Baltazar ◽  
Elisa Cairrao
Keyword(s):  
Blood Flow ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Blood Vessels ◽  
Neurovascular Unit ◽  
Muscle Cells ◽  
Cerebral Blood Vessels ◽  
Mural Cells ◽  
Brain Pericytes ◽  
The Brain

The neurovascular unit is a physiological unit present in the brain, which is constituted by elements of the nervous system (neurons and astrocytes) and the vascular system (endothelial and mural cells). This unit is responsible for the homeostasis and regulation of cerebral blood flow. There are two major types of mural cells in the brain, pericytes and smooth muscle cells. At the arterial level, smooth muscle cells are the main components that wrap around the outside of cerebral blood vessels and the major contributors to basal tone maintenance, blood pressure and blood flow distribution. They present several mechanisms by which they regulate both vasodilation and vasoconstriction of cerebral blood vessels and their regulation becomes even more important in situations of injury or pathology. In this review, we discuss the main regulatory mechanisms of brain smooth muscle cells and their contributions to the correct brain homeostasis.

Edema, Fainting, and Strokes

2021 ◽  
pp. 216-240
Author(s):  
Graham Mitchell
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Blood Vessels ◽  
High Blood Pressure ◽  
Fluid Pressure ◽  
Basement Membranes ◽  
Tissue Pressure ◽  
Efficient Mechanisms ◽  
The Brain ◽  
Mediated Reduction

High blood pressure in humans is often associated with heart failure, edema, strokes, and episodes of fainting. Giraffes never show these. Edema, the abnormal collection of fluid in the lower legs, is prevented in giraffes by a combination of thick basement membranes of capillary blood vessels, which probably reduce their permeability to proteins, a very high tissue pressure that resists flow of fluid out of capillaries, and efficient mechanisms for returning blood to the heart. Fainting occurs when blood flow (and thus oxygen and glucose supply) to the brain is reduced. When a giraffe lifts its head after drinking water there is a sudden reduction of blood flow to the head, and fainting should result. Fainting is avoided because the blood flow that remains is diverted completely to the brain by a unique arrangement of blood vessels and nerves, and by structures that maintain the perfusion pressure of the blood flowing through the brain. Strokes can be caused by rupture of small blood vessels in the brain when they are exposed to high blood pressure of the kind reached in the head of a giraffe when it drinks surface water. Rupture of brain blood vessels is prevented in giraffes by mechanisms that reduce pressure. The posture adopted while drinking, baroreceptor-mediated reduction in cardiac output, the effects of the carotid rete, diversion of blood away from the brain, an increase in cerebrospinal fluid pressure, and passive and active constriction of blood vessels, all contribute.

MODELING REDISTRIBUTION CEREBRAL CIRCULATION

2021 ◽  
Vol 1 (4) ◽  
pp. 13-18
Author(s):  
Vladislav Nikolaevich Nikitin ◽  
◽  
Ekaterina Valerevna Kozhemyakina ◽  
Keyword(s):  
Blood Flow ◽  
Internal Carotid ◽  
Cerebral Arteries ◽  
Circle Of Willis ◽  
Entire Body ◽  
Compensatory Mechanisms ◽  
Vertebral Arteries ◽  
The Central Nervous System ◽  
Flow Through ◽  
The Brain

The brain is one of the most important organs responsible for the health and functioning of the entire body. The blood supply to the brain is carried out through 2 internal carotid and 2 vertebral arteries in norm. The brain, like other body systems, has protective (compensatory) mechanisms aimed at maintaining the necessary blood flow, one of which is the circle of Willis. The article proposes a mechanism for how blood flow is redistributed through the arteries feeding the brain, which is based on the assumption that the central nervous system controls in such a way that it minimizes flows through the connective arteries of the circle of Willis, the flows along which are normal (with symmetry of the left and right sides) practically equal to zero. Сase of the structure of the circle of Willis is considered in norm. The indicated redistribution mechanism is still only the first step towards an attempt to predict cases of changes in blood flow through the cerebral arteries, especially in stroke. In further works, it is planned to consider the inverse problem, i.e. determine the flows through the internal carotid and vertebral arteries, provided that the flows through the cerebral arteries extending from the circle of Willis have normal flow values.

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