Biomedical Engineering and Bioengineering Commons^™

Transcatheter Heart Valve Subassembly Device, Adam Aslam, Matthew Bezkrovny, Daniel Degree

Mechanical Engineering

No abstract provided.

Continuous Size-Based Separation Of Microparticles In A Microchannel With Symmetric Sharp Corner Structures, Liang-Liang Fan, Xu-Kun He, Yu Hun, Li Du, Liang Zhao, Jiang Zhe

Dr. Jiang Zhe

A new microchannel with a series of symmetric sharp corner structures is reported for passive size-dependent particle separation. Micro particles of different sizes can be completely separated based on the combination of the inertial lift force and the centrifugal force induced by the sharp corner structures in the microchannel. At appropriate flow rate and Reynolds number, the centrifugal force effect on large particles, induced by the sharp corner structures, is stronger than that on small particles; hence after passing a series of symmetric sharp corner structures, large particles are focused to the center of the microchannel, while small particles are …

Novel Materials For The Direct Removal Of Water And Ions From The Body For Patients With Dialysis Needs, Lisa Furby, Ravinder Gupta, Ajay Mahajan, Jarlen Don, Tsuchin Chu, Bakul Dave, Bradley Schwartz

Dr. Ajay Mahajan

This paper describes a novel material for the direct removal of water and ions from the body of patients with End Stage Renal Disease (ESRD). The work is part of a larger project that is envisioned to be a new type of dialysis process that could replace or enhance existing dialysis methods. The main idea is to implant a unit either and/or outside the body of the patients with renal failure so that they do not have to go through the painstaking and exhausting hemodialysis or peritoneal dialysis processes existing today. The proposed work in its final embodiment will eliminate …

Construction And Validation Of A Complaint Model Of The Cerebrospinal Fluid System With Fluid Filled Syrinx, Bryn Martin, Wojciech Kalata, John Oshinski, Francis Loth, Thomas Royston

Dr. Bryn Martin

No abstract provided.

Pathological Biomechanics Of Cerebrospinal Fluid Pressure In Syringomyelia: Fluid Structure Interaction Of An In Vitro Coaxial Elastic Tube System, Bryn Martin, Richard Labuda, Thomas Royston, John Oshinski, Bermans Iskandar, Francis Loth

Dr. Bryn Martin

Full explanation for the formation and pathogenesis of syringomyelia (SM), a neurological pathology characterized by the formation of a cystic cavity (syrinx) in the center of the spinal cord (SC), has not yet been given. The SM pathology forms a coaxial elastic tube system with the inner tube formed by the spinal cord having a syrinx and the outer tube formed by the spinal column (dura and vertebrae).

The Influence Of Coughing On Cerebrospinal Fluid Pressure In An In Vitro Syringomyelia Model With Spinal Canal Stenosis, Bryn Martin, Francis Loth

Dr. Bryn Martin

Five in vitro models were constructed which were representative of various pathologies of the spinal canal (SC) associated with syringomyelia (SM). The models were subjected to a cough type flow impulse while monitoring the pressure environment in the syrinx and subarachnoid space (SAS) regions of the model. The results indicated that conditions can arise during a cough which would provide pressure forces to encourage cerebrospinal fluid (CSF) movement into the syrinx cavity.

A Multimode Sonic And Ultrasonic Diagnostic Imaging System With Application To Peripheral Vascular Characterization, Todd Spohnholtz, Thomas Royston, Yigit Yazicioglu, Bryn Martin, Francis Loth

Dr. Bryn Martin

No abstract provided.

Characterization Of The Discrepancies Between Four-Dimensional Phase-Contrast Magnetic Resonance Imaging And In-Silico Simulations Of Cerebrospinal Fluid Dynamics, Soroush Heidari, Alexander Bunck, Francis Loth, R. Tubbs, Theresia Yiallourou, Jan Kroeger, Walter Heindel, Bryn Martin

Dr. Bryn Martin

The purpose of the present study was to compare subject-specific magnetic resonance imaging (MRI)-based computational fluid dynamics (CFD) simulations with time-resolved three-directional (3D) velocity-encoded phase-contrast MRI (4D PCMRI) measurements of the cerebrospinal fluid (CSF) velocity field in the cervical spinal subarachnoid space (SSS). Three-dimensional models of the cervical SSS were constructed based on MRI image segmentation and anatomical measurements for a healthy subject and patient with Chiari I malformation. CFD was used to simulate the CSF motion and compared to the 4D PCMRI measurements. Four-dimensional PCMRI measurements had much greater CSF velocities compared to CFD simulations (1.4 to 5.6× greater). …

Quantitative Comparison Of 4d Mri Flow Measurements To 3d Computational Fluid Dynamics Simulation Of Cerebrospinal Fluid Movement In The Spinal Subarachnoid Space, Theresia Yiallourou, Leonie Asboth, J. Kroeger, David Maintz, A. Bunck, Nikolaos Stergiopulos, Bryn Martin

Dr. Bryn Martin

Computational fluid dynamic (CFD) simulations have provided detailed information about the complex flow and pressure field within the cerebrospinal fluid (CSF) system. The solutions of these simulations are sensitive to boundary conditions and thus need validation with in vivo measurements. However, validation of CFD flow results and MRI CSF flow measurements have been limited to through-plane pcMR measurements.

Impact Of Aortic Grafts On Hemodynamics: A 1d Computational Assessment, O. Vardoulis, E. Coppens, Bryn Martin, P. Reymond, N. Stergiopulos

Dr. Bryn Martin

Vascular prostheses currently used in aortic replacement surgery do not have the same mechanical properties as human arteries. In vivo studies have revealed that aortic grafts augment heart load and alter blood pressure and flow waveforms. A one-dimensional model of the arterial tree was developed in order to analyze the different mechanisms by which grafts placed in the ascending aorta (proximal) and descending aorta (distal) affect hemodynamics. Graft compliance and properties were based on in vitro tests

A Coupled Simulation Of Spinal Cord Blood Flow And Cerebrospinal Fluid Motion In The Spinal Subarachnoid Space Based On In Vivo Measurements, Bryn Martin, Philippe Reymond, Olivier Baledent, Jan Novy, Nikos Stergiopulos

Dr. Bryn Martin

A preliminary coupled 1-D model of the systemic arterial tree and cerebrospinal fluid (CSF) system was constructed. The systemic tree model includes arteries greater than 2 mm in diameter and a simplified spinal cord vasculature. Coupling of the arterial tree and CSF system is accomplished by a transfer function based on in vivo cerebral blood flow (CBF) and CSF pulsation measurements in 17 young healthy adults.

Spinal Subarachnoid Space Pressure Measurements In An In Vitro Spinal Stenosis Model: Implications On Syringomyelia Theories, Bryn Martin, Richard Labuda, Thomas Royston, John Oshinski, Bermans Iskandar, Francis Loth

Dr. Bryn Martin

Full explanation for the pathogenesis of syringomyelia (SM), a neuropathology characterized by the formation of a cystic cavity (syrinx) in the spinal cord (SC), has not yet been provided. It has been hypothesized that abnormal cerebrospinal fluid (CSF) pressure, caused by subarachnoid space (SAS) flow blockage (stenosis), is an underlying cause of syrinx formation and subsequent pain in the patient.

Coupled Vibration Of A Fluid‐Filled And Submerged Vascular Tube With Internal Transitional/ Turbulent Flow Due To A Constriction, Yigit Yazicioglu, Thomas Royston, Todd Spohnholtz, Bryn Martin, Francis Loth

Dr. Bryn Martin

No abstract provided.

Mr Measurement Of Cerebrospinal Fluid Velocity Wave Speed In The Spinal Canal, Wojciech Kalata, Bryn Martin, John Oshinski, Michael Jerosch-Herold

Dr. Bryn Martin

Noninvasive measurement of the speed with which the cere-brospinal fluid (CSF) velocity wave travels through the spinal canal is of interest as a potential indicator of CSF system pressure and compliance, both of which may play a role in the development of craniospinal diseases. However, measurement of CSF velocity wave speed (VWS) has eluded researchers primarily due to either a lack of access to CSF velocity measurements or poor temporal resolution.

Syringomyelia Hydrodynamics: An In Vitro Study Based On In Vivo Measurements, Bryn Martin, Wojciech Kalata, Francis Loth, Thomas Royston, John Oshinski

Dr. Bryn Martin

A simplified in vitro model of the spinal canal, based on in vivo magnetic resonance imaging, was used to examine the hydrodynamics of the human spinal cord and subarachnoid space with syringomyelia. In vivo magnetic resonance imaging (MRI) measurements of subarachnoid (SAS) geometry and cerebrospinal fluid velocity were acquired in a patient with syringomyelia and used to aid in the in vitro model design and experiment. The in vitro model contained a fluid-filled coaxial elastic tube to represent a syrinx.

Acoustic Radiation From A Fluid-Filled, Subsurface Vascular Tube With Internal Turbulent Flow Due To A Constriction, Yigit Yazicioglu, Thomas Royston, Todd Spohnholtz, Bryn Martin, Francis Loth, Hisham Bassiouny

Dr. Bryn Martin

The vibration of a thin-walled cylindrical, compliant viscoelastic tube with internal turbulent flow due to an axisymmetric constriction is studied theoretically and experimentally. Vibration of the tube is considered with internal fluid coupling only, and with coupling to internal-flowing fluid and external stagnant fluid or external tissue-like viscoelastic material. The theoretical analysis includes the adaptation of a model for turbulence in the internal fluid and its vibratory excitation of and interaction with the tube wall and surrounding

Towards Non-Invasive Assessment Of The Elastic Properties Of The Spinal Aqueduct, Bryn Martin, Thomas Royston, John Oshinski, Francis Loth

Dr. Bryn Martin

Analytical models are developed for cerebrospinal fluid (CSF) pressure wave propagation speed based on viscoelastic properties and geometry of the subarachnoid space (SAS). The models were compared to experimental tests on various compliant coaxial tube phantom models of the spinal SAS having different thicknesses and mechanical properties, with the ultimate goal of developing a noninvasive in vivo technique for determining the elastic properties of the spinal aqueduct.

Assessment Of Aortic Graft Impact On Hemodynamics, Orestis Vardoulis, Bryn Martin, Philippe Reymond, Nikos Stergiopulos

Dr. Bryn Martin

In vivo studies have revealed that aortic grafts augment heart load and alter blood pressure and flow waveforms [1]. A one-dimensional model of the arterial tree was developed in order to analyze the different mechanisms by which proximal and distal aortic grafts affect hemodynamics. Graft compliance and properties were based on in vitro tests. Predicted pressures at the aortic root were compared for the control, proximal and distal graft case.

Magnetic Resonance 4d Flow Analysis Of Cerebrospinal Fluid Dynamics In Chiari I Malformation With And Without Syringomyelia, Alexander Bunck, Jan Kroger, Alena Juettner, Angela Brentrup, Barbara Fiedler, Gerard Crelier, Bryn Martin, Walter Heindel, David Maintz, Wolfram Scwindt, Thomas Niederstadt

Dr. Bryn Martin

Objective

To analyse cerebrospinal fluid (CSF) hydrodynamics in patients with Chiari type I malformation (CM) with and without syringomyelia using 4D magnetic resonance (MR) phase contrast (PC) flow imaging.

Hydrodynamics Of Cerebrospinal Fluid In Spinal Canal With Chiari Malformation And Syringomyelia, Wojciech Kalata, Bryn Martin, Josh Oshinski, Francis Loth

Dr. Bryn Martin

No abstract provided.

The Effect Of Continuous Positive Airway Pressure On Total Cerebral Blood Flow In Healthy Awake Volunteers, Theresia Yiallourou, Celine Odier, Raphael Heinzer, Lorenz Hirt, Bryn Martin, Nikolaos Stergiopulos

Dr. Bryn Martin

Continuous positive airway pressure (CPAP) is the gold standard treatment for obstructive sleep apnea. However, the physiologic impact of CPAP on cerebral blood flow (CBF) is not well established. Ultrasound can be used to estimate CBF, but there is no widespread accepted protocol. We studied the physiologic influence of CPAP on CBF using a method integrating arterial diameter and flow velocity (FV) measurements obtained for each vessel supplying blood to the brain.

Ventricle Equilibrium Position In Healthy And Normal Pressure Hydrocephalus Brains Using An Analytical Model, K. Shahim, J. Drezet, Bryn Martin, S. Momjian

Dr. Bryn Martin

The driving force that causes enlargement of the ventricles remains unclear in case of normal pressure hydrocephalus (NPH). Both healthy and NPH brain conditions are characterized by a low transparenchymal pressure drop, typically 1 mm Hg. The present paper proposes an analytical model for normal and NPH brains using Darcy’s and Biot’s equations and simplifying the brain geometry to a hollow sphere with an internal and external radius. Self-consistent solutions for the large deformation problem that is associated with large ventricle dilation are presented and the notion of equilibrium or stable ventricle position is highlighted for both healthy and NPH …

Comparison Of 4d Phase-Contrast Mri Flow Measurements To Computational Fluid Dynamics Simulations Of Cerebrospinal Fluid Motion In The Cervical Spine, Theresia Yiallourou, Jan Robert Kroger, Nikolaos Stergiopulos, David Maintz, Bryn A. Martin, Alexander C. Bunck

Dr. Bryn Martin

Cerebrospinal fluid (CSF) dynamics in the cervical spinal subarachnoid space (SSS) have been thought to be important to help diagnose and assess craniospinal disorders such as Chiari I malformation (CM). In this study we obtained time-resolved three directional velocity encoded phase-contrast MRI (4D PC MRI) in three healthy volunteers and four CM patients and compared the 4D PC MRI measurements to subject-specific 3D computational fluid dynamics (CFD) simulations. The CFD simulations considered the geometry to be rigid-walled and did not include small anatomical structures such as nerve roots, denticulate ligaments and arachnoid trabeculae. Results were compared at nine axial planes …

A Coupled Hydrodynamic Model Of The Cardiovascular And Cerebrospinal Fluid System, Bryn Martin, Philippe Reymond, Jan Reymond, Jan Novy, Olivier Baledent, Nikolaos Stergiopulos

Dr. Bryn Martin

Coupling of the cardiovascular and cerebrospinal fluid (CSF) system is considered to be important to understand the pathophysiology of cerebrovascular and craniospinal disease and intrathecal drug delivery. A coupled cardiovascular and CSF system model was designed to examine the relation of spinal cord (SC) blood flow (SCBF) and CSF pulsations along the spinal subarachnoid space (SSS). A one-dimensional (1-D) cardiovascular tree model was constructed including a simplified SC arterial network. Connection between the cardiovascular and CSF system was accomplished by a transfer function based on in vivo measurements of CSF and cerebral blood flow. A 1-D tube model of the …