Engineering Commons^™

A Novel Method For Characterization Of Peripheral Nerve Fiber Size Distributions By Group Delay, Robert B. Szlavik

Biomedical Engineering

The ability to determine the characteristics of peripheral nerve fiber size distributions would provide additional information to clinicians for the diagnosis of specific pathologies of the peripheral nervous system. Investigation of these conditions, using electrodiagnostic techniques, is advantageous in the sense that such techniques tend to be minimally invasive yet provide valuable diagnostic information. One of the principal electrodiagnostic tools available to the clinician is the nerve conduction velocity test. While the peripheral nerve conduction velocity test can provide useful information to the clinician regarding the viability of the nerve under study, it is a single-parameter test that yields no …

Monitoring Tissue Engineering Using Magnetic Resonance Imaging, Huihui Xu, Shadi F. Othman, Richard L. Magin

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Assessment of tissue regeneration is essential to optimize the stages of tissue engineering (cell proliferation, tissue development and implantation). Optical and X-ray imaging have been used in tissue engineering to provide useful information, but each has limitations: for example, poor depth penetration and radiation damage. Magnetic resonance imaging (MRI) largely overcomes these restrictions, exhibits high resolution (approximately 100 μm) and can be applied both in vitro and in vivo. Recently, MRI has been used in tissue engineering to generate spatial maps of tissue relaxation times (T₁, T₂), water diffusion coefficients, and the stiffness (shear moduli) of …

Characterization Of Vascular Smooth Muscle Cell Mechanical And Frictional Properties Using Atomic Force Microscopy, Jason Hemmer

All Dissertations

A working hypothesis within the Laboratory of Vascular Research is that mechanical loading on vascular smooth muscle cells (VSMCs), especially due to solid contact from endovascular devices, contributes to the development of restenosis. In order to better understand the role of mechanical loading on VSMCs in vascular disease development, it is imperative to understand the mechanical properties of VSMCs themselves. To measure the viscoelastic and frictional properties of living VSMCs in an in vitro setting, an atomic force microscope (AFM) was utilized, thereby allowing for mechanical testing of living cells in a fluid environment. In the first phase of research, …

Effect Of Clinically Relevant Mechanical Forces On Smooth Muscle Cell Response In Model Of Balloon Angioplasty, Kara Acampora

All Dissertations

Restenosis remains a common problem affecting the patency of endovascular intervention such as balloon angioplasty and stent placement as treatments for atherosclerosis. Denudation of the endothelial layer and the increased injury from balloon deployment can cause phenotypic changes in surrounding vascular smooth muscle cells (SMCs) in vivo. The presented work modeled this mechanical environment in vitro to investigate the role of the altered mechanical environment on the phenotypic response of SMCs. Through the system design and CFD channel characterization, a six-independent-channel system providing low oscillating wall shear stress (WSS) was manufactured to apply concurrent shear and tensile forces with uniform …

Vascular Tissue Engineering: The Creation Of Living, Non-Thrombogenic, Functional Blood Vessels Based On Elastin Scaffolds, Aditee Kurane

All Dissertations

Cardiovascular diseases are the leading cause of death worldwide. Blood vessel replacement is a common treatment for vascular diseases such as atherosclerosis, restenosis and aneurysm, with over 300,000 bypass procedures performed each year. However, vein grafts are limited due to their availability. Although synthetic vascular replacements have been successful for large diameter arteries, they have shown minimal success in arteries with diameters <6mm. This is because most synthetic materials induce thrombus formation which, within a few months of implantation, causes failure of the vascular graft due to occlusion. Tissue engineering is a promising approach to the fabrication of non-thrombogenic vascular grafts, but a reliable and expandable cell source for tissue-engineered vascular graft (TEVG) has not been established.
The work presented here is motivated by the current unavailability of an ideal tissue engineered blood vessel replacement. Our overall goal is to create a living tissue engineered vascular graft that is biodegradable, non-thromobogenic, presents low antigenicity and …

Ecm Stabilization Strategies For Bioprosthetic Heart Valves For Improved Durability, Devanathan Raghavan

All Dissertations

Abstract
Approximately 85,000 heart valve replacement surgeries are performed every year in United States and about 300,000 surgeries worldwide. It is estimated that half of them are mechanical valve replacements and the other half bioprosthetic valve replacements. The use of bioprosthetic heart valves is slowly increasing. Bioprosthetic heart valves are made from porcine aortic valves or bovine pericardium. Commercially these bioprostheses are currently crosslinked using glutaraldehyde (GLUT) to prevent tissue degradation and reduce tissue antigenicity. GLUT crosslinks these bioprostheses by stabilizing the collagen present in the tissue via a Schiff base reaction of the aldehyde with the hydroxylysine / lysine …

A Device For Noninvasive Assessment Of Vascular Impairment Risk In The Lower Extremity, Michael J. Hoffmann, Paul E. Knudson, M. Barbara Silver-Thorn

Biomedical Engineering Faculty Research and Publications

The repeatability and resolution of the clinical gold standard of vascular assessment, the ankle-brachial index (ABI), was compared to that of a new device that dynamically assesses tissue perfusion during external loading utilizing laser Doppler flowmetry. Eight subjects of varying levels of vascular impairment were tested in successive weeks using two different sites on the subject's posterior calf. These new measures included the perfusion decrease as well as the unloading delay during cyclic loading. Some new dynamic tissue perfusion measures demonstrated comparable levels of reproducibility with the ABI (e.g., 10%-20%). Only the unloading delay showed potentially enhanced resolution over ABI …

Synthesis And Characterization Of Novel Temperature-Responsive Dendritic Peg-Pdlla Star Polymers For Drug Delivery, Arunvel Kailasan

Theses and Dissertations

This study describes a novel thermoresponsive dendritic polyethylene glycol-poly(D, L-lactide) (PEG-PDLLA) core-shell nanoparticle with potential for drug delivery and controlled release. A series of dendritic PEG-PDLLA nanoparticles were synthesized through conjugation of PEG to Starburst™ polyamidoamine (PAMAM) dendrimer G3.0 and subsequent ring-opening polymerization of DLLA, in which PEG chain length (i.e., MW=1500, 6000 or 12000 Dalton) was varied; however, the feeding molar ratio of DLLA monomers to the overall PEG repeat units on the dendrimer surface was kept at 1:1. Linear PEG-PDLLA copolymers were also syntheiszed under the same condition and used as control. According to our results, dendritic PEG-PDLLA …

Accelerometer Based Measurement Of Body Movement For Communication, Play, And Creative Expression, Mark Nolan, Edward Burke, Frank Duignan

Conference Papers

This paper presents a newly designed wireless accelerometer-based movement measurement device. The device is capable of measuring activity ranging from gross body movements to more subtle vibrations emanating from the body, including laryngeal vibration and the mechanomyogram (mechanical vibrations from working muscles). The main body of the device, which is less than 20cm3 in volume and weighs less than 50g, contains a microcontroller, wireless transceiver, battery, and one accelerometer. A supplementary accelerometer module is connected to the main device by thin wires. This module is very light weight and can therefore be directly attached to the skin to measure laryngeal …

Angiogenic Potential Of Human Macrophages On Electrospun Bioresorbable Vascular Grafts, Koyal Garg

Theses and Dissertations

The aim of this study was to investigate macrophage interactions with electrospun scaffolds and quantify the expression of vital angiogenic growth factors in vitro. This study will further help in evaluating the potential of these electrospun constructs as vascular grafts for tissue repair and regeneration in situ. Human peripheral blood macrophages were seeded in serum free media on electrospun (10 mm) discs of polydioxanone (PDO), elastin and PDO:elastin blends (50:50, 70:30 and 90:10). The growth factor secretion was analyzed by ELISA. Macrophages produced high levels of vascular endothelial growth factor (VEGF) and acidic fibroblast growth factor (aFGF). Transforming growth factor …

Extracellular Matrix Protein Orientation By Adsorption On Self-Assembled Monolayers Controls Nonviral Gene Delivery, Beth A. Duensing, Angela K. Pannier

Department of Agricultural and Biological Systems Engineering: Presentations and White Papers

To date, most efforts to understand and improve the efficiency of nonviral gene delivery have focused on altering the physicochemical properties of delivery systems and developing new delivery strategies. The importance of the cellular microenvironment in achieving successful nonviral gene transfer has not been thoroughly examined, though proteins of the extracellular matrix (ECM) mediate cell adhesion and serve to regulate cellular behavior that may, in turn, dictate the cellular responsiveness to nonviral gene delivery. Self-assembled monolayers (SAMs) of alkanethiols on gold were used to control adsorption of ECM molecules and thus control the architecture of the extracellular environment presented to …

Design And Optimization Of A Blood Vessel Mimic Bioreactor System For The Evaluation Of Intravascular Devices In Simple And Complex Vessel Geometries, Sara M. Leifer

Master's Theses

Coronary artery disease affects millions of people and the ability to detect and treat the disease is advancing at a rapid rate. As a result, the development of intravascular technologies is the focus of many medical device manufacturers. Specifically, coronary stent implantation is being performed in an increasing number of patients and a number of new stent designs have been introduced to the market, resulting in the need for improved preclinical testing methods. An in vitro tissue engineered “blood vessel mimic” (BVM) system has previously been established and its feasibility for the initial testing of newly emerging intravascular technology has …

Methodology Development For Three-Dimensional Mr-Guided Near Infrared Spectroscopy Of Breast Tumors, Colin M. Carpenter, Subhadra Srinivasan, Brian W. Pogue, Keith D. Paulsen

Dartmouth Scholarship

Combined Magnetic Resonance (MR) and Near Infrared Spectroscopy (NIRS) has been proposed as a unique method to quantify hemodynamics, water content, and cellular size and packing density of breast tumors, as these tissue constituents can be quantified with increased resolution and overlaid on the structural features identified by the MR. However, the choices in how to reconstruct and visualize this information can have a dramatic impact on the feasibility of implementing this modality in the clinic. This is especially true in 3 dimensions, as there is often limited optical sampling of the breast tissue, and methods need to accurately reflect …

Implantable Biosensors For Real-Time Strain And Pressure Monitoring, Ee Lim Tan, Brandon D. Pereles, Brock Horton, Ranyuan Shao, Mohammed Zourob, Keat Ghee Ong

Michigan Tech Publications, Part 1

Implantable biosensors were developed for real-time monitoring of pressure and strain in the human body. The sensors, which are wireless and passive, consisted of a soft magnetic material and a permanent magnet. When exposed to a low frequency AC magnetic field, the soft magnetic material generated secondary magnetic fields that also included the higher-order harmonic modes. Parameters of interest were determined by measuring the changes in the pattern of these higher-order harmonic fields, which was achieved by changing the intensity of a DC magnetic field generated by a permanent magnet. The DC magnetic field, or the biasing field, was altered …

Teaching Physiology To Biomedical Engineers Using Team-Based Learning And Inquiry Research, Trevor R. Cardinal

Biomedical Engineering

Presentation given at conference.

Stochastic Event Reconstruction Of Atmospheric Contaminant Dispersion Using Bayesian Inference, Inanc Senocak, Nicolas W. Hengartner, Margaret B. Short, W. Brent Daniel

Mechanical and Biomedical Engineering Faculty Publications and Presentations

Environmental sensors have been deployed in various cities for early detection of contaminant releases into the atmosphere. Event reconstruction and improved dispersion modeling capabilities are needed to estimate the extent of contamination, which is required to implement effective strategies in emergency management. To this end, a stochastic event reconstruction capability that can process information from an environmental sensor network is developed. A probability model is proposed to take into account both zero and non-zero concentration measurements that can be available from a sensor network because of a sensor’s specified limit of detection. The inference is based on the Bayesian paradigm …

Volume Effects On Yield Strength Of Equine Cortical Bone, R. F. Bigley, J. C. Gibeling, S. M. Stover, S. J. Hazelwood, D. P. Fyhrie, R. B. Martin

Biomedical Engineering

Volume effects are a fundamental determinant of structural failure. A material exhibits a volume effect if its failure properties are dependent on the specimen volume. Many brittle ceramics exhibit volume effects due to loading a structure in the presence of “critical” flaws. The number of flaws, their locations, and the effect of stress field within the stressed volume play a role in determining the structure’s failure properties. Since real materials are imperfect, structures composed of large volumes of material have higher probabilities of containing a flaw than do small volumes. Consequently, large material volumes tend to fail at lower stresses …

Parameter Estimation Of The Arterial System, James Charles Carter Ii

Mechanical & Aerospace Engineering Theses & Dissertations

There are a number of disorders that originate from or involve faulty operation of the cardiovascular system. Diseases such as atherosclerosis, diabetes and hypertension can have a debilitating effect on blood flow. This makes the tools for simulating the effects of such diseases on blood flow important. Measures, such as pulse wave velocity, that are generated by models of the cardiovascular system can be important indicators of cardiac health. Although physically measurable, obtaining some parameters comes with a high cost and discomfort to the patient. Models can provide an assessment of many important parameters. The purpose of this project was …

Sequestration And Ultrasound-Induced Release Of Doxorubicin From Stabilized Pluronic P105 Micelles, John D. Pruitt, William G. Pitt

Faculty Publications

Controlled drug delivery from micelles requires that the micelles remain stable when diluted below their critical micelle concentration, such as upon injection into blood. A cross-linked, interpenetrating network of N,N-diethylacrylamide (NNDEA) was polymerized in the core of Pluronic P105 micelles to stabilize temporarily the micelles at concentrations below the critical micellar concentration of free P105. The stabilized Pluronic micelles (called Plurogels) were able to sequester the drug doxorubicin (Dox) and protect HL-60 cells from the drug at concentrations where non-stabilized Pluronic provided no protection. The protection lasted ~ 12 hr, which is similar to the half-life of the particles. Application …

Fatigue Testing Of Three Peristernal Median Sternotomy Closure Techniques, Cameron Wangsgard, David J. Cohen, Lanny V. Griffin

Biomedical Engineering

Failure of a sternotomy closure because of closure system fatigue is a complication that may result in dehiscence and put the individual at risk for serious complications. The purpose of this study was to assess the fatigue performance of three peristernal median sternotomy closure techniques (figure-of-eight stainless-steel wires, figure-of-eight stainless-steel cables, or Pectofix Dynamic Sternal Fixation [DSF] stainless-steel plates) in order to quantify the potential risk of fatigue failure of these devices when subject to cyclic loads in physiologically relevant loading directions.

Metabolic Engineering Of A Thermophilic Bacterium To Produce Ethanol At High Yield, A. Joe Shaw, Kara K. Podkaminer, Sunil G. Desai, John S. Bardsley, Stephen R. Rogers, Philip G. Thorne, David A. Hogsett, Lee R. Lynd

Dartmouth Scholarship

We report engineering Thermoanaerobacterium saccharolyticum, a thermophilic anaerobic bacterium that ferments xylan and biomass-derived sugars, to produce ethanol at high yield. Knockout of genes involved in organic acid formation (acetate kinase, phosphate acetyltransferase, and L-lactate dehydrogenase) resulted in a strain able to produce ethanol as the only detectable organic product and substantial changes in electron flow relative to the wild type. Ethanol formation in the engineered strain (ALK2) utilizes pyruvate:ferredoxin oxidoreductase with electrons transferred from ferredoxin to NAD(P), a pathway different from that in previously described microbes with a homoethanol fermentation. The homoethanologenic phenotype was stable for >150 generations …

An Engineering Evaluation Of Ankle Prosthetics, Christopher Thian, Stephen Tiernan, Fiona Mcevoy, Robert Flavin

Conference Papers

There are a wide range of different types of ankle replacements on the market today each with a
different mechanical design. Unfortunately the results of ankle replacements are not as good as hip
and knee replacements; this is due to the complexity of the ankle joint. In the early days of ankle
replacements some of the prosthetics only lasted 4 months. Recent developments have improved the
longevity of the replacements although, there are still many complications and failures of the
replacements, these include; the prosthetic components migrating into the bone, the components
failing due to stresses induced by the forces …

Assessment Of The Effects Of Increasing Levels Of Physiological Realism In The Computational Fluid Dynamics Analyses Of Implanted Coronary Stents, Jonathan Murphy, Fergal Boyle

Conference Papers

Coronary stent implantation can improve blood flow in an artery that has been narrowed by the build up of arterial plaque. However, the implantation of the stent will change the geometry of the vessel wall. The haemodynamic effects of the stents presence and alteration of the vessel wall are unclear. The redistribution of flow induced vessel wall shear stress (WSS) and wall shear stress gradient (WSSG) may directly contribute to restenosis (re-blockage). Computational fluid dynamics (CFD) is used extensively to identify these parameters in stented vessels. However, simplifications to the model of the stented artery are common. In this paper, …

Cephalometric Analysis Using Magnetic Resonance Imaging, Wade A. Williams

Loma Linda University Electronic Theses, Dissertations & Projects

Purpose: The purpose of this study was to determine if T1-weighted 3D magnetic resonance images performed at 3.0 Tesla could be used to conduct routine orthodontic cephalometric analysis.

Methods: Three cranial imaging methods were compared using sixteen non-growing subjects (10 male and 6 female) who were not claustrophobic, did not have any metallic restorations on the distal of first molars, had no medical implants and the female subjects were not pregnant. Sagittal cranial images were produced by three methods: (1) a digital lateral cephalometric (LC) radiograph (Orthophos XG Plus, Sirona^TM, Bensheim, Germany), (2) a 12-inch FOV cone beam …

Enhanced Na+/H+ Exchange During Ischemia And Reperfusion Impairs Mitochondrial Bioenergetics And Myocardial Function, Mohammed Aldakkak, David F. Stowe, James S. Heisner, Marisha Spence, Amadou K.S. Camara

Biomedical Engineering Faculty Research and Publications

Inhibition of Na+/H+ exchange (NHE) during ischemia reduces cardiac injury due to reduced reverse mode Na+/Ca2+ exchange. We hypothesized that activating NHE-1 at buffer pH 8 during ischemia increases mitochondrial oxidation, Ca2+ overload, and reactive O2 species (ROS) levels and worsens functional recovery in isolated hearts and that NHE inhibition reverses these effects. Guinea pig hearts were perfused with buffer at pH 7.4 (control) or pH 8 +/- NHE inhibitor eniporide for 10 minutes before and for 10 minutes after 35- minute ischemia and then for 110 minutes with pH 7.4 buffer alone. Mitochondrial NADH and FAD, [Ca2+], and superoxide …

Low-Flow Perfusion Of Guinea Pig Isolated Hearts With 26°C Air-Saturated Lifor Solution For 20 Hours Preserves Function And Metabolism, David F. Stowe, Amadou K.S. Camara, James S. Heisner, Mohammed Aldakkak, David R. Harder

Biomedical Engineering Faculty Research and Publications

Background

Donor human hearts cannot be preserved for >5 hours between explantation and recipient implantation. A better approach is needed to preserve transplantable hearts for longer periods, ideally at ambient conditions for transport. We tested whether Lifor solution could satisfactorily preserve guinea pig isolated hearts perfused at low flow with no added oxygen at room temperature for 20 hours.

Methods

Hearts were isolated from 18 guinea pigs and perfused initially with oxygenated Krebs–Ringer (KR) solution at 37°C. Hearts were then perfused with recirculated Lifor or cardioplegia (CP) solution (K⁺ 15 mmol/liter) equilibrated with room air at 20% of control …

Classification Of Hand Held Shapes And Locations In Continuous Signing, Swetha Karri

Theses

Sign language for the deaf and hearing impaired replaces speech with manually produced signs. Each sign has been categorized as being combinations of handshape, movement, orientation, location, and facial expressions. Of the five sign parameters, this thesis focuses on classification of two of the main parameters, the hand shapes and locations, in continuous signing.

Since the nature of hand shapes is transient and not static, neural networks was used as a classifier for hand shapes. And since locations in sign language are defined by linguistic variables rather than by hard core position values, fuzzy logic was used as a classifier …

Photoplethysmorgraph-Derived Respiration, Priyanka Pankaj Shah

Theses

Stress & Motivated Behavioral Institute (SMBI) has developed a research program to provide an objective evaluation of the physiological and neurocognitive impact of human electromuscular muscular interference (HEMI) devices in humans. The initial step is to understand their physiological impact, which is characterized by vital signs. Volunteers are recruited from HEMI training programs with the provision that data collection can not interfere with training. Thus, an ambulatory system was assembled. There are two main issues in the current ambulatory system, one of which is the reliability of the respiration signal obtained using a strain gauge respiration band, mainly due to …

Design And Fabrication Of A Microneedle For The Implantation Of Floating Microstimulators, Faysal Ahmed

Theses

Neural prosthetics are used to stimulate any remaining functional nervous tissue in order to restore function in visual, auditory, or other physiological components associated with the nervous system. Microelectrodes have been used in stimulating and detecting electrical activity in neurons. When stimulating or recording neural tissue activity using microelectrodes, there are usually many problems and difficulties in obtaining the correct functionality and results. There is great difficulty in placing these microelectrodes in a specific location in the central nervous system due to various problems with the methodology used. Many different techniques such as the traditional interconnected microelectrodes have been an …

Biomechanical Testing Of Upright Range Of Motion Versus Overhead Supine Range Of Motion, Linda Uko

Theses

Rehabilitation of an elbow, following injury, is not a well-studied subject. Clinically, there is not a general consensus on which recovery method is optimal for healing an unstable elbow. When dealing with medial collateral ligament deficiency, many authors have proposed several forearm positions that will yield proper healing of the unstable elbow. Some researchers believe that active mobilization of the elbow with the arm in a vertical position is a safe protocol for rehabilitation with the forearm oriented in a supine pronated position. It was also mentioned that the compressive forces due to the active mobilization of the arm will …