Biomedical Engineering and Bioengineering Commons^™

Parallel Facilitatory Reflex Pathways From The Foot And Hip To Flexors And Extensors In The Injured Human Spinal Cord, Maria Knikou, Elizabeth Kay, Brian D. Schmit

Biomedical Engineering Faculty Research and Publications

Spinal integration of sensory signals associated with hip position, muscle loading, and cutaneous sensation of the foot contributes to movement regulation. The exact interactive effects of these sensory signals under controlled dynamic conditions are unknown. The purpose of the present study was to establish the effects of combined plantar cutaneous afferent excitation and hip movement on the Hoffmann (H) and flexion reflexes in people with a spinal cord injury (SCI). The flexion and H-reflexes were elicited through stimulation of the right sural (at non-nociceptive levels) and posterior tibial nerves respectively. Reflex responses were recorded from the ipsilateral tibialis anterior (TA) …

Reach Adaptation And Final Position Control Amid Environmental Uncertainty After Stroke, Robert A. Scheidt, Tina M. Stoeckmann

Biomedical Engineering Faculty Research and Publications

We characterized how hemiparetic stroke survivors and neurologically intact individuals adapt reaching movements to compensate for unpredictable environmental perturbations. We tested the hypotheses that like unimpaired subjects, hemiparetic stroke survivors adapt using sensory information obtained during only the most recent movements and that the reliability of target acquisition decreases as the degree of sensorimotor impairment increases. Subjects held the handle of a two-joint robotic arm that applied forces to the hand while reaching between targets in a horizontal plane. The robot simulated a dynamic environment that varied randomly in strength from one trial to the next. The trial sequence of …

Neural And Electromyographic Correlates Of Wrist Posture Control, Aaron J. Suminski, Stephen M. Rao, Kristine M. Mosier, Robert A. Scheidt

Biomedical Engineering Faculty Research and Publications

In identical experiments in and out of a MR scanner, we recorded functional magnetic resonance imaging and electromyographic correlates of wrist stabilization against constant and time-varying mechanical perturbations. Positioning errors were greatest while stabilizing random torques. Wrist muscle activity lagged changes in joint angular velocity at latencies suggesting trans-cortical reflex action. Drift in stabilized hand positions gave rise to frequent, accurately directed, corrective movements, suggesting that the brain maintains separate representations of desired wrist angle for feedback control of posture and the generation of discrete corrections. Two patterns of neural activity were evident in the blood-oxygenation-level-dependent (BOLD) time series …

Quantifying Kinematics Of Purposeful Movements To Real, Imagined, Or Absent Functional Objects: Implications For Modelling Trajectories For Robot-Assisted Adl Tasks, Kimberly J. Wisneski, Michelle J. Johnson

Biomedical Engineering Faculty Research and Publications

Background

Robotic therapy is at the forefront of stroke rehabilitation. The Activities of Daily Living Exercise Robot (ADLER) was developed to improve carryover of gains after training by combining the benefits of Activities of Daily Living (ADL) training (motivation and functional task practice with real objects), with the benefits of robot mediated therapy (repeatability and reliability). In combining these two therapy techniques, we seek to develop a new model for trajectory generation that will support functional movements to real objects during robot training. We studied natural movements to real objects and report on how initial reaching movements are affected by …

Distensibility Differs Between Sall Arteries And Veins In The Newborn Piglet Lung, John B. Gordon, Steven Thomas Haworth, Robert C. Molthen, Gary S. Krenz, Anne V. Clough

Biomedical Engineering Faculty Research and Publications

BACKGROUND: We previously used micro-CT techniques to measure pulmonary artery distensibility in 3 week old piglets. Pressure/diameter relationships were measured for each artery and the slope (a) was then plotted against its diameter intercept at 0 pressure (Do). The resultant diameter independent distensibility parameter, a, was estimated by linear regression to be 1.6% per mmHg for arteries between 0.2 and 3.0 mm Do.

OBJECTIVE: This study sought to determine whether; 1) distensibility of smaller arteries was similar to that of arteries with Do> 0.2 mm; and 2) whether small vein and artery distensibility was similar.

DESIGN/METHODS: Lower lobes were isolated …

Modulation Of Stretch Reflexes Of The Finger Flexors By Sensory Feedback From The Proximal Upper Limb Poststroke, Gilles Hoffmann, Derek G. Kamper, Jennifer H. Kahn, William Zev Rymer, Brian D. Schmit

Biomedical Engineering Faculty Research and Publications

Neural coupling of proximal and distal upper limb segments may have functional implications in the recovery of hemiparesis after stroke. The goal of the present study was to investigate whether the stretch reflex response magnitude of spastic finger flexor muscles poststroke is influenced by sensory input from the shoulder and the elbow and whether reflex coupling of muscles throughout the upper limb is altered in spastic stroke survivors. Through imposed extension of the metacarpophalangeal (MCP) joints, stretch of the relaxed finger flexors of the four fingers was imposed in 10 relaxed stroke subjects under different conditions of proximal sensory input, …

Pre- And Post-Alpha Motoneuronal Control Of The Soleus H-Reflex During Sinusoidal Hip Movements In Human Spinal Cord Injury, Maria Knikou, Debjani Chaudhuri, Elizabeth Kay, Brian D. Schmit

Biomedical Engineering Faculty Research and Publications

The aim of this study was to establish the contribution of hip-mediated sensory feedback to spinal interneuronal circuits during dynamic conditions in people with incomplete spinal cord injury (SCI). Specifically, we investigated the effects of synergistic and antagonistic group I afferents on the soleus H-reflex during imposed sinusoidal hip movements. The soleus H-reflex was conditioned by stimulating the common peroneal nerve (CPN) at short (2, 3, and 4 ms) and long (80, 100, and 120 ms) conditioning test (C-T) intervals to assess the reciprocal and pre-synaptic inhibition of the soleus H-reflex, respectively. The soleus H-reflex was also conditioned by medial …

99mTc-Labeled C2a Domain Of Synaptotagmin I As A Target-Specific Molecular Probe For Noninvasive Imaging Of Acute Myocardial Infarction, Ming Zhao, Xiaoguang Zhu, Shundong Ji, Jundong Zhou, Kutlan S. Ozker, Wei Fang, Robert C. Molthen, Robert S. Hellman

Biomedical Engineering Faculty Research and Publications

Abstract: The exposure of phosphatidylserine (PtdS) is a common molecular marker for both apoptosis and necrosis and enables the simultaneous detection of these distinct modes of cell death. Our aim was to develop a radiotracer based on the PtdS-binding activity of the C2A domain of synaptotagmin I and assess ^99mTc-C2A-GST (GST is glutathione S-transferase) using a reperfused acute myocardial infarction (AMI) rat model. Methods: The binding of C2A-GST toward apoptosis and necrosis was validated in vitro. After labeling with ^99mTc via 2-iminothiolane thiolation, radiochemical purity and radiostability were tested. Pharmacokinetics and biodistribution were studied in healthy rats. …

Alterations In Regional Vascular Geometry Produced By Theoretical Stent Implantation Influence Distributions Of Wall Shear Stress: Analysis Of A Curved Coronary Artery Using 3d Computational Fluid Dynamics Modeling, John F. Ladisa, Lars E. Olson, Douglas Anthony Hettrick, David C. Warltier, Judy R. Kersten, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Background

The success of stent implantation in the restoration of blood flow through areas of vascular narrowing is limited by restenosis. Several recent studies have suggested that the local geometric environment created by a deployed stent may influence regional blood flow characteristics and alter distributions of wall shear stress (WSS) after implantation, thereby rendering specific areas of the vessel wall more susceptible to neointimal hyperplasia and restenosis. Stents are most frequently implanted in curved vessels such as the coronary arteries, but most computational studies examining blood flow patterns through stented vessels conducted to date use linear, cylindrical geometric models. It …

A Prototype Table-Top Inverse-Geometry Volumetric Ct System, Taly Gilat Schmidt, Josh Star-Lack, N. Robert Bennett, Samuel R. Mazin, Edward G. Solomon, Rebecca Fahrig, Norbert J. Pelc

Biomedical Engineering Faculty Research and Publications

A table-top volumetric CT system has been implemented that is able to image a 5-cm-thick volume in one circular scan with no cone-beam artifacts. The prototype inverse-geometry CT (IGCT) scanner consists of a large-area, scanned x-ray source and a detector array that is smaller in the transverse direction. The IGCT geometry provides sufficient volumetric sampling because the source and detector have the same axial, or slice direction, extent. This paper describes the implementation of the table-top IGCT scanner, which is based on the NexRay Scanning-Beam Digital X-ray system (NexRay, Inc., Los Gatos, CA) and an investigation of the system performance. …

Explant Analysis Of Total Disc Replacement, Paul A. Anderson, Steven M. Kurtz, Jeffrey M. Toth

Biomedical Engineering Faculty Research and Publications

Explant analysis of human disc prostheses allow early evaluation of the host response to the prosthesis and the response of the prosthesis from the host. Furthermore, early predictions of failure and wear can be obtained. Thus far, about 2-3% of disc prostheses have been removed. Observed wear patterns are similar to that of appendicular prostheses including abrasions/scratching, burnishing, surface deformation, fatigue, and embedded debris. Chemically the polymeric components have shown little degradation in short-term implantation. In metal on metal prostheses the histologic responses consist of large numbers of metallic particles with occasional macrophages and giant cells. Only rare cases of …

Vascular Tortuosity Is Culprit To Abnormal Perfusion In 9l Gliosarcoma Tumor, M. M. Darpolar, Robert C. Molthen, F. C. Wu, Kathleen M. Schmainda

Biomedical Engineering Faculty Research and Publications

No abstract provided.

Lung Circulation Modeling: Status And Prospect, Anne V. Clough, Said H. Audi, Robert C. Molthen, Gary S. Krenz

Biomedical Engineering Faculty Research and Publications

Mathematical modeling has been used to interpret anatomical and physiological data obtained from metabolic and hemodynamic studies aimed at investigating structure-function relationships in the vasculature of the lung, and how these relationships are affected by lung injury and disease. The indicator dilution method was used to study the activity of redox processes within the lung. A steady-state model of the data was constructed and used to show that pulmonary endothelial cells may play an important role in reducing redox active compounds and that those reduction rates can be altered with oxidative stress induced by exposure to high oxygen environments. In …

Influence Of Pulmonary Arterial Endothelial Cells On Quinone Redox Status: Effect Of Hyperoxia-Induced Nad(P)H:Quinone Oxidoreductase 1, Marilyn P. Merker, Said H. Audi, Robert D. Bongard, Brian J. Lindemer, Gary S. Krenz

Biomedical Engineering Faculty Research and Publications

The objective of this study was to examine the impact of chronic hyperoxic exposure (95% O₂ for 48 h) on intact bovine pulmonary arterial endothelial cell redox metabolism of 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ). DQ or durohydroquinone (DQH₂) was added to normoxic or hyperoxia-exposed cells in air-saturated medium, and the medium DQ concentrations were measured over 30 min. DQ disappeared from the medium when DQ was added and appeared in the medium when DQH₂ was added, such that after ∼15 min, a steady-state DQ concentration was approached that was ∼4.5 times lower for the hyperoxia-exposed than the normoxic …

Ischemia Reperfusion Dysfunction Changes Model-Estimated Kinetics Of Myofilament Interaction Due To Inotropic Drugs In Isolated Hearts, Samhita S. Rhodes, Amadou Ks Camara, Kristina M. Ropella, Said H. Audi, Matthias L. Riess, Paul S. Pagel, David F. Stowe

Biomedical Engineering Faculty Research and Publications

Background

The phase-space relationship between simultaneously measured myoplasmic [Ca²⁺] and isovolumetric left ventricular pressure (LVP) in guinea pig intact hearts is altered by ischemic and inotropic interventions. Our objective was to mathematically model this phase-space relationship between [Ca²⁺] and LVP with a focus on the changes in cross-bridge kinetics and myofilament Ca²⁺ sensitivity responsible for alterations in Ca²⁺-contraction coupling due to inotropic drugs in the presence and absence of ischemia reperfusion (IR) injury.

Methods

We used a four state computational model to predict LVP using experimentally measured, averaged myoplasmic [Ca²⁺] transients …

Resistance To Fracture Of Two All-Ceramic Crown Materials Following Endodontic Access, Kelly Copps Wood, David W. Berzins, Qing Luo, Geoffrey A. Thompson, Jeffrey M. Toth, William W. Nagy

Biomedical Engineering Faculty Research and Publications

Statement of problem

There is currently no protocol for managing endodontic access openings for all-ceramic crowns. A direct restorative material is generally used to repair the access opening, rendering a repaired crown as the definitive restoration. This endodontic procedure, however, may weaken the restoration or initiate microcracks that may propagate, resulting in premature failure of the restoration.

Purpose

The purpose of this in vitro study was to evaluate how an endodontic access opening prepared through an all-ceramic crown altered the structural integrity of the ceramic, and the effect of a repair of this access on the load to failure of …

Recent Trends In Robot-Assisted Therapy Environments To Improve Real-Life Functional Performance After Stroke, Michelle J. Johnson

Biomedical Engineering Faculty Research and Publications

Upper and lower limb robotic tools for neuro-rehabilitation are effective in reducing motor impairment but they are limited in their ability to improve real world function. There is a need to improve functional outcomes after robot-assisted therapy. Improvements in the effectiveness of these environments may be achieved by incorporating into their design and control strategies important elements key to inducing motor learning and cerebral plasticity such as mass-practice, feedback, task-engagement, and complex problem solving.

This special issue presents nine articles. Novel strategies covered in this issue encourage more natural movements through the use of virtual reality and real objects and …

Polyetheretherketone As A Biomaterial For Spinal Applications, Jeffrey M. Toth, Mei Wang, Bradley T. Estes, Jeffrey L. Scifert, Howard B. Seim, A. Simon Turner

Biomedical Engineering Faculty Research and Publications

Threaded lumbar interbody spinal fusion devices (TIBFD) made from titanium have been reported to be 90% effective for single-level lumbar interbody fusion, although radiographic determination of fusion has been intensely debated in the literature. Using blinded radiographic, biomechanic, histologic, and statistical measures, we evaluated a radiolucent polyetheretherketone (PEEK)-threaded interbody fusion device packed with autograft or rhBMP-2 on an absorbable collagen sponge in 13 sheep at 6 months. Radiographic fusion, increased spinal level biomechanical stiffness, and histologic fusion were demonstrated for the PEEK cages filled with autograft or rhBMP-2 on a collagen sponge. No device degradation or wear debris was observed. …

A Simple, Inexpensive, And Effective Light- Carrying Laryngoscopic Blade For Orotracheal Intubation Of Rats, Robert C. Molthen

Biomedical Engineering Faculty Research and Publications

The research paradigm of using large laboratory animals, in which oroendotracheal intubations are relatively easy, is shifting toward the use of small animals, such as rodents, in which oropharyngeal access is limited, the arytenoid cartilage cycles are faster, and the glottis is much smaller. The considerable growth recently seen in preclinical imaging studies is accompanied by an increased number of rats and mice requiring in vivo intubation for airway management. Tracheal access is important for ventilation, administration of inhaled anesthetics, instillation of drugs or imaging agents, and maintenance of airway patency to reduce mortality during and after operations. I fashioned …

Motivating Rehabilitation By Distorting Reality, James L. Patton, Yejun Wei, Chris Scharver, Robert V. Kenyon, Robert A. Scheidt

Biomedical Engineering Faculty Research and Publications

We have found, through a series of recent experiments, encouraging evidence that the neuro-motor system is motivated to change motor patterns when exposed to visuo-motor tasks. We have also shown that the learning of these tasks can be heightened with forces and/or visual distortions that appropriately manipulate the error. This process does not require intense concentration and it is often considered a game. We describe the next generation of robotic large-workspace, three dimensional haptics/graphics systems for rehabilitation

Remapping Hand Movements In A Novel Geometrical Environment, Kristine M. Mosier, Robert A. Scheidt, Santiago Acosta, Ferdinando A. Mussa-Ivaldi

Biomedical Engineering Faculty Research and Publications

The issue of how the Euclidean properties of space are represented in the nervous system is a main focus in the study of visual perception, but is equally relevant to motor learning. The goal of our experiments was to investigate how the properties of space guide the remapping of motor coordination. Subjects wore an instrumented data glove that recorded the finger motions. Signals generated by the glove operated a remotely controlled endpoint: a cursor on a computer monitor. The subjects were instructed to execute movements of this endpoint with controlled motions of the fingers. This required inverting a highly redundant …

Effect Of Chronic Hyperoxic Exposure On Duroquinone Reduction In Adult Rat Lungs, Said H. Audi, Robert D. Bongard, Gary S. Krenz, David A. Rickaby, Steven Thomas Haworth, Jessica Eisenhauer, David L. Roerig, Marilyn P. Merker

Biomedical Engineering Faculty Research and Publications

NAD(P)H:quinone oxidoreductase 1 (NQO1) plays a dominant role in the reduction of the quinone compound 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ) to durohydroquinone (DQH₂) on passage through the rat lung. Exposure of adult rats to 85% O₂ for ≥7 days stimulates adaptation to the otherwise lethal effects of >95% O₂. The objective of this study was to examine whether exposure of adult rats to hyperoxia affected lung NQO1 activity as measured by the rate of DQ reduction on passage through the lung. We measured DQH₂ appearance in the venous effluent during DQ infusion at different concentrations into …

A Three-Dimensional Reconstruction Algorithm For An Inverse-Geometry Volumetric Ct System, Taly Gilat Schmidt, Rebecca Fahrig, Norbert J. Pelc

Biomedical Engineering Faculty Research and Publications

An inverse-geometry volumetric computed tomography (IGCT) system has been proposed capable of rapidly acquiring sufficient data to reconstruct a thick volume in one circular scan. The system uses a large-area scanned source opposite a smaller detector. The source and detector have the same extent in the axial, or slice, direction, thus providing sufficient volumetric sampling and avoiding cone-beam artifacts. This paper describes a reconstruction algorithm for the IGCT system. The algorithm first rebins the acquired data into two-dimensional (2D) parallel-ray projections at multiple tilt and azimuthal angles, followed by a 3D filtered backprojection. The rebinning step is performed by gridding …

Axial Stent Strut Angle Influences Wall Shear Stress After Stent Implantation: Analysis Using 3d Computational Fluid Dynamics Models Of Stent Foreshortening, John F. Ladisa, Lars E. Olson, Douglas Anthony Hettrick, David C. Warltier, Judy R. Kersten, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Introduction

The success of vascular stents in the restoration of blood flow is limited by restenosis. Recent data generated from computational fluid dynamics (CFD) models suggest that the vascular geometry created by an implanted stent causes local alterations in wall shear stress (WSS) that are associated with neointimal hyperplasia (NH). Foreshortening is a potential limitation of stent design that may affect stent performance and the rate of restenosis. The angle created between axially aligned stent struts and the principal direction of blood flow varies with the degree to which the stent foreshortens after implantation.

Methods

In the current investigation, we …

Microfocal X-Ray Computed Tomography Post-Processing Operations For Optimizing Reconstruction Volumes Of Stented Arteries During 3d Computational Fluid Dynamics Modeling, John F. Ladisa, Lars E. Olson, Kristina M. Ropella, Robert C. Molthen, Steven Thomas Haworth, Judy R. Kersten, David C. Warltier, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Restenosis caused by neointimal hyperplasia (NH) remains an important clinical problem after stent implantation. Restenosis varies with stent geometry, and idealized computational fluid dynamics (CFD) models have indicated that geometric properties of the implanted stent may differentially influence NH. However, 3D studies capturing the in vivo flow domain within stented vessels have not been conducted at a resolution sufficient to detect subtle alterations in vascular geometry caused by the stent and the subsequent temporal development of NH. We present the details and limitations of a series of post-processing operations used in conjunction with microfocal X-ray CT imaging and reconstruction to …

Interaction Of Visual And Proprioceptive Feedback During Adaptation Of Human Reaching Movements, Robert A. Scheidt, Michael A. Conditt, Emanuele L. Secco, Ferdinando A. Mussa-Ivaldi

Biomedical Engineering Faculty Research and Publications

People tend to make straight and smooth hand movements when reaching for an object. These trajectory features are resistant to perturbation, and both proprioceptive as well as visual feedback may guide the adaptive updating of motor commands enforcing this regularity. How is information from the two senses combined to generate a coherent internal representation of how the arm moves? Here we show that eliminating visual feedback of hand-path deviations from the straight-line reach (constraining visual feedback of motion within a virtual, “visual channel”) prevents compensation of initial direction errors induced by perturbations. Because adaptive reduction in direction errors occurred with …

Alterations In Wall Shear Stress Predict Sites Of Neointimal Hyperplasia After Stent Implantation In Rabbit Iliac Arteries, John F. Ladisa, Lars E. Olson, Robert C. Molthen, Douglas Anthony Hettrick, Phillip F. Pratt, Michael D. Hardel, Judy R. Kersten, David C. Warltier, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Restenosis resulting from neointimal hyperplasia (NH) limits the effectiveness of intravascular stents. Rates of restenosis vary with stent geometry, but whether stents affect spatial and temporal distributions of wall shear stress (WSS) in vivo is unknown. We tested the hypothesis that alterations in spatial WSS after stent implantation predict sites of NH in rabbit iliac arteries. Antegrade iliac artery stent implantation was performed under angiography, and blood flow was measured before casting 14 or 21 days after implantation. Iliac artery blood flow domains were obtained from three-dimensional microfocal X-ray computed tomography imaging and reconstruction of the arterial casts. Indexes of …

Circumferential Vascular Deformation After Stent Implantation Alters Wall Shear Stress Evaluated With Time-Dependent 3d Computational Fluid Dynamics Models, John F. Ladisa, Lars E. Olson, Ismail Guler, Douglas Anthony Hettrick, Judy R. Kersten, David C. Warltier, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

The success of vascular stents in the restoration of blood flow is limited by restenosis. Recent data generated from computational fluid dynamics (CFD) models suggest that stent geometry may cause local alterations in wall shear stress (WSS) that have been associated with neointimal hyperplasia and subsequent restenosis. However, previous CFD studies have ignored histological evidence of vascular straightening between circumferential stent struts. We tested the hypothesis that consideration of stent-induced vascular deformation may more accurately predict alterations in indexes of WSS that may subsequently account for histological findings after stenting. We further tested the hypothesis that the severity of these …

Antegrade Iliac Artery Stent Implantation For The Temporal And Spatial Examination Of Stent-Induced Neointimal Hyperplasia And Alterations In Regional Fluid Dynamics, John F. Ladisa, Heidi T. Meier, Lars E. Olson, Judy R. Kersten, David C. Warltier, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Neointimal hyperplasia remains an important problem after stent implantation. Previous investigations examining vascular responses to stent implantation and effects of drugs have used a retrograde deployment approach that may inadvertently alter the local fluid dynamics surrounding the stent. We present a model of antegrade iliac artery stent implantation that facilitates the analysis of stent-induced alterations in neointimal hyperplasia and wall shear stress in vivo. Methods: Stent delivery catheters were inserted through the left carotid artery in anesthetized rabbits (n=37). Catheters were advanced under fluoroscopic guidance to the distal iliac arteries, where the stent was deployed. Hemotoxylin and eosin …

An In Vitro Comparison Of The Rake Angles Between K3 And Profile Endodontic File Systems, David Y. Chow, Sheila E. Stover, James Bahcall, Andris Jaunberzins, Jeffrey M. Toth

Biomedical Engineering Faculty Research and Publications

The purpose of this study was to compare rake angles of the ProFile and K3 file systems. Twenty-five 40/0.06 taper files were obtained for each system. Five files from the same manufacturer were placed perpendicularly into a vial of Epoxicure Resin and left to set for 24 h. The set-ups were removed from the vials and each were sectioned 5 mm from the tip of the files and polished. A photomicrograph was taken of each file with 100× magnification. Five sets of ProFile and five sets of K3 files were processed in this manner. Images were captured digitally, and rake …