Biomedical Engineering and Bioengineering Commons^™

Effects Of Wrist Tendon Vibration On Arm Tracking In People Poststroke, Megan O. Conrad, Robert A. Scheidt, Brian D. Schmit

Biomedical Engineering Faculty Research and Publications

The goal of this study was to evaluate the influence of wrist tendon vibration on a multijoint elbow/shoulder tracking task. We hypothesized that tendon vibration applied at the wrist musculature would improve upper arm tracking performance in chronic stroke survivors through increased, Ia-afferent feedback to the central nervous system (CNS). To test this hypothesis, 10 chronic stroke and 5 neurologically intact subjects grasped the handle of a planar robot as they tracked a target through a horizontal figure-8 pattern. A total of 36 trials were completed by each subject. During the middle trials, 70-Hz tendon vibration was applied at the …

Computational Simulations For Aortic Coarctation: Representative Results From A Sampling Of Patients, John F. Ladisa, Alberto Figueroa, Irene E. Vignon-Clementel, Hyun Jin Kim, Nan Xiao, Laura M. Ellwein, Frandics P. Chan, Jeffrey A. Feinstein, Charles A. Taylor

Biomedical Engineering Faculty Research and Publications

Treatments for coarctation of the aorta (CoA) can alleviate blood pressure (BP) gradients(D), but long-term morbidity still exists that can be explained by altered indices of hemodynamics and biomechanics. We introduce a technique to increase our understanding of these indices for CoA under resting and nonresting conditions, quantify their contribution to morbidity, and evaluate treatment options. Patient-specific computational fluid dynamics (CFD) models were created from imaging and BP data for one normal and four CoA patients (moderate native CoA: D12 mmHg, severe native CoA: D25 mmHg and postoperative end-to-end and end-to-side patients: D0 mmHg). Simulations incorporated vessel deformation, downstream vascular …

Computational Simulations Demonstrate Altered Wall Shear Stress In Aortic Coarctation Patients Previously Treated By Resection With End-To-End Anastomosis, John F. Ladisa, Ronak Jashwant Dholakia, Alberto Figueroa, Irene E. Vignon-Clementel, Frandics P. Chan, Margaret M. Samyn, Joseph Richard Cava, Charles A. Taylor, Jeffrey A. Feinstein

Biomedical Engineering Faculty Research and Publications

Background.  Atherosclerotic plaque in the descending thoracic aorta (dAo) is related to altered wall shear stress (WSS) for normal patients. Resection with end-to-end anastomosis (RWEA) is the gold standard for coarctation of the aorta (CoA) repair, but may lead to altered WSS indices that contribute to morbidity.

Methods.  Computational fluid dynamics (CFD) models were created from imaging and blood pressure data for control subjects and age- and gender-matched CoA patients treated by RWEA (four males, two females, 15 ± 8 years). CFD analysis incorporated downstream vascular resistance and compliance to generate blood flow velocity, time-averaged WSS (TAWSS), and oscillatory shear …

Spatial And Temporal Variation Of Rod Photoreceptor Reflectance In The Human Retina, Robert F. Cooper, Adam M. Dubis, Ashavini M. Pavaskar, Jungtae Rha, Alfredo Dubra, Joseph Carroll

Biomedical Engineering Faculty Research and Publications

Using adaptive optics imaging tools to image the living retina, numerous investigators have reported temporal fluctuation in the reflectivity of individual cone photoreceptors. In addition, there is cone-to-cone (spatial) variation in reflectivity. As it has only recently become possible to image the complete rod photoreceptor mosaic in the living human retina, we sought to characterize the reflectivity of individual rods and compare their behavior to that of foveal/parafoveal cones. Across two subjects, we were able to successfully track the reflectance behavior of 1,690 rods and 1,980 cones over 12 hours. Rod and cone photoreceptors showed similar regional and temporal variability …

Carotid Plaque Regression Following 6-Month Statin Therapy Assessed By 3t Cardiovascular Magnetic Resonance: Comparison With Ultrasound Intima Media Thickness, Raymond Q. Migrino, Mark Bowers, Leanne Harmann, Robert W. Prost, John F. Ladisa

Biomedical Engineering Faculty Research and Publications

Background

Cardiovascular magnetic resonance (CMR) allows volumetric carotid plaque measurement that has advantage over 2-dimensional ultrasound (US) intima-media thickness (IMT) in evaluating treatment response. We tested the hypothesis that 6-month statin treatment in patients with carotid plaque will lead to plaque regression when measured by 3 Tesla CMR but not by IMT.

Methods

Twenty-six subjects (67 ± 2 years, 7 females) with known carotid plaque (> 1.1 mm) and coronary or cerebrovascular atherosclerotic disease underwent 3T CMR (T1, T2, proton density and time of flight sequences) and US at baseline and following 6 months of statin therapy (6 had initiation, …

Global Flow Impacts Time-To-Passage Judgments Based On Local Motion Cues, Scott A. Beardsley, Elif M. Sikoglu, Heiko Hecht, Lucia M. Vaina

Biomedical Engineering Faculty Research and Publications

We assessed the effect of the coherence of optic flow on time-to-passage judgments in order to investigate the strategies that observers use when local expansion information is reduced or lacking. In the standard display, we presented a cloud of dots whose image expanded consistent with constant observer motion. The dots themselves, however, did not expand and were thus devoid of object expansion cues. Only the separations between the dots expanded. Subjects had to judge which of two colored target dots, presented at different simulated depths and lateral displacements would pass them first. Image velocities of the target dots were chosen …

Sensorimotor Control Of 3d Arm Movement And Stability In Post-Stroke Hemiparesis, Kakanand Alfonsomarie Srungboonmee

Dissertations (1934 -)

Deficits of the affected arm in people with post-stroke hemiparesis have been generally associated with decreased strength and increased spasticity. These deficits are varied in proximal (shoulder) and distal (elbow) joints which results in an overall impairment during movement or during stabilization of hand position in space. In this study, reaching of the hemiparetic arm in 3D workspace was characterized by a curved and non-smooth endpoint trajectory and a reduced functional range of motion, compared to the unimpaired arm. Smoother trajectories were observed in the acceleration phase more than the deceleration phase, which was common to both the stroke subjects …

Role Of Tendon Vibration In Multijoint Reflex Coupling In The Hemiparetic Arm Post Stroke, Bani Gadhoke

Master's Theses (2009 -)

Post stroke hemiparesis causes reflex coupling in multiple muscles of the arm, leading to atypical movements that hamper motor control. In particular, people post-stroke can become unstable while holding the arm at the end of a planar motion. Recently, we have found that tendon vibration of the wrist flexors improves the stability of the arm during a hold task. The objective of the current study was to identify the effects of vibration applied to the wrist flexors on the biceps and triceps stretch reflexes, generated using a tendon tapper. In people post-stroke, tendon tap perturbations of the biceps and triceps …

Detection Of Specific Biological Antigens Using Ac Electrochemical Impedance Spectroscopy, Darrel Angelo Mazzari

Dissertations (1934 -)

When certain antigens are present in our environment, a rapid, on-site, accurate, selective, and repeatable detection method can be invaluable in preventing illness or saving lives. Rapid detection of these antigens is important to avert spreading infections.

Currently, capturing a sample and sending it to a laboratory can take weeks to get results, which can be much too long. Conventional sensing methodologies include various electrical measurements as capacitive, potentiometric, piezoelectric, surface plasmon resonance (SPR), and quartz crystal microbalance (QCM). Of particular power and interest is Alternating Current (AC) Electrochemical Impedance Spectroscopy (EIS) which provides for the characterization of the electrical …

Modeling And Computational Framework For The Specification And Simulation Of Large-Scale Spiking Neural Networks, David James Herzfeld

Master's Theses (2009 -)

Recurrently connected neural networks, in which synaptic connections between neurons can form directed cycles, have been used extensively in the literature to describe various neurophysiological phenomena, such as coordinate transformations during sensorimotor integration. Due to the directed cycles that can exist in recurrent networks, there is no well-known way to a priori specify synaptic weights to elicit neuron spiking responses to stimuli based on available neurophysiology. Using a common mean field assumption, that synaptic inputs are uncorrelated for sufficiently large populations of neurons, we show that the connection topology and a neuron's response characteristics can be decoupled. This assumption allows …

Asymmetric Transfer Of Task Dependent Perceptual Learning In Visual Motion Processing, Sampada Charudatta Wakde

Master's Theses (2009 -)

The effects of perceptual learning (PL) on the sensory representation are not fully understood, especially for higher–level visual mechanisms more directly relevant to behavior. The objective of this research is to elucidate the mechanisms that mediate task dependent learning by determining where and how task dependent learning occurs in the later stages of visual motion processing.

Eighteen subjects were trained to perform a dual–2TAFC visual discrimination task in which they were required to simultaneously detect changes in the direction of moving dots (task–1) and the proportion of red dots (task–2) shown in two stimulus apertures presented in either the left …

Differential Responses Of Targeted Lung Redox Enzymes To Rat Exposure To 60 Or 85% Oxygen, Zhuohui Gan, David L. Roerig, Anne V. Clough, Said H. Audi

Biomedical Engineering Faculty Research and Publications

Rat exposure to 60% O₂ (hyper-60) or 85% O₂ (hyper-85) for 7 days confers susceptibility or tolerance, respectively, of the otherwise lethal effects of exposure to 100% O₂. The objective of this study was to determine whether activities of the antioxidant cytosolic enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1) and mitochondrial complex III are differentially altered in hyper-60 and hyper-85 lungs. Duroquinone (DQ), an NQO1 substrate, or its hydroquinone (DQH₂), a complex III substrate, was infused into the arterial inflow of isolated, perfused lungs, and the venous efflux rates of DQH₂ and DQ were measured. …

Adaptive Real-Time Decoding Of Brain Signals For Long-Term Control Of A Neuro-Prosthetic Device, Tushar Ashok Dharampal

Master's Theses (2009 -)

Changes in the statistical properties of neural signals recorded at the brain machine interface (BMI) pose significant challenges for accurate long-term control of prostheses interfaced directly with the brain by continuously altering the relationship between neural responses and desired action. In this thesis, we develop and test an adaptive decoding algorithm that can recover from changes in the statistical properties of neural signals within minutes. The adaptive decoding algorithm uses a Kalman filter as part of a dual-filter design to continuously optimize the relationship between the observed neural responses and the desired action of the prosthesis. Performance of the algorithm …

Examining The Relationships Among Injury Outcomes, Velocity And Grip Strength During Dynamic Platform Perturbation, Braden Cripe

Master's Theses (2009 -)

Studies examining the relationship between inputs and outputs for simulated models of dynamically perturbed horizontal platforms are scarce. Most of these scenarios include a standing operator with upper extremity grip, oftentimes subjected to lateral impulses, which may lead to occupant injury. While the detailed study of these collision scenarios is sparse, the prevalence of their application is great.

This thesis aims to identify how two input parameters, velocity change (ÄV) and grip strength, affect injury assessment reference values (IARVs). This is accomplished by using Mathematical Dynamic Modeling (MADYMO) software to simulate the scenarios defined by those inputs. In the simulation, …

Methods For Detecting High-Frequency Oscillations In Ongoing Brain Signals: Application To The Determination Of Epileptic Seizure Onset Zones, Chiran Dilip Doshi

Master's Theses (2009 -)

Epilepsy is a neurological disorder with varied expression. Patients with focal onset seizures that are resistant to medications can benefit from ablative surgery. However, localization of the seizure onset zone (SOZ) and characterization of propagation to secondary areas can be challenging. The present study aimed at developing the appropriate signal processing methodology to detect bursts of interictal high-frequency oscillations (HFOs), as a possible signature of the SOZ, in patients with drug-resistant partial epilepsy. Additionally, invasive interictal and ictal intracranial electroencephalography (iEEG) data and non-invasive electromagnetic source imaging with magnetoencephalography (MEG) data from three subjects were analyzed. We developed a novel …

Tools For Creating Wide-Field Views Of The Human Retina Using Optical Coherence Tomography, Ashavini M. Pavaskar

Master's Theses (2009 -)

Optical Coherence Tomography (OCT) has allowed in-vivo viewing of details of retinal layers like never before. With the development of spectral domain OCT (SD-OCT) details of nearly 2µm axial resolution and higher imaging speed have been reported. Nevertheless, a single volume scan of the retina is typically restricted to 6mm x 6mm in size. Having a larger field of view of the retina will definitely enhance the clinical utility of the OCT.

A tool was developed for creating wide-field thickness maps of the retina by combining the use of already available tools like i2k Retina (DualAlign, LLC, Clifton Park, NY) …

Development Of An Experimental Model To Quantify Lumbar Spine Kinematics During Military Seat Ejection, Steven George Storvik

Master's Theses (2009 -)

The initial phase of a military ejection sequence exerts substantial axial loads on the spinal column. Eccentric inertial loading on the thoracolumbar spine can lead to injury. Most serious injuries due to ejection are in the form of a vertebral fracture, most commonly occurring at the thoracolumbar junction. The objective of the current study was to understand characteristics of a military seat ejection by employing an experimental model designed to simulate the boost or in-rail phase. The model incorporates realistic boundary conditions and is capable of quantifying metrics associated with injury tolerance such as applied accelerations and resultant loads and …

Noninvasive Imaging Of The Human Rod Photoreceptor Mosaic Using A Confocal Adaptive Optics Scanning Ophthalmoscope, Alfredo Dubra, Yusufu N. Sulai, Jennifer L. Norris, Robert F. Cooper, Adam M. Dubis, David R. Williams, Joseph Carroll

Biomedical Engineering Faculty Research and Publications

The rod photoreceptors are implicated in a number of devastating retinal diseases. However, routine imaging of these cells has remained elusive, even with the advent of adaptive optics imaging. Here, we present the first in vivo images of the contiguous rod photoreceptor mosaic in nine healthy human subjects. The images were collected with three different confocal adaptive optics scanning ophthalmoscopes at two different institutions, using 680 and 775 nm superluminescent diodes for illumination. Estimates of photoreceptor density and rod:cone ratios in the 5°–15° retinal eccentricity range are consistent with histological findings, confirming our ability to resolve the rod mosaic by …

Effect Of Ankle Orientation On Heel Loading And Knee Stability For Post-Stroke Individuals Wearing Ankle-Foot Orthoses, M. Barbara Silver-Thorn

Biomedical Engineering Faculty Research and Publications

Background: Those who experience lower extremity weakness or paralysis following a stroke often exhibit gait deviations caused by the inability to completely lift their foot during swing. An ankle-foot orthosis (AFO) is commonly prescribed for individuals post stroke with this mobility impairment.

Study design: Randomized controlled trial.

Objectives: To determine whether significant differences could be observed in post-stroke individuals ambulating with an experimental AFO set at three different ankle orientations.

Methods: Gait analysis was conducted for eight post-stroke individuals ambulating with an experimental AFO set in three different randomly selected ankle orientations: 5° dorsiflexion, 5° plantarflexion, and neutral alignment. Temporospatial …

Salen Mn Complexes Mitigate Radiation Injury In Normal Tissues, Rosalind A. Rosenthal, Brian Fish, Richard P. Hill, Karl D. Huffman, Zelmira Lazarova, Javed Mahmood, Meetha Medhora, Robert C. Molthen, John E. Moulder, Stephen T. Sonis, Philip J. Tofilon, Susan R. Doctrow

Biomedical Engineering Faculty Research and Publications

Salen Mn complexes, including EUK-134, EUK-189 and a newer cyclized analog EUK-207, are synthetic SOD/catalase mimetics that have beneficial effects in many models of oxidative stress. As oxidative stress is implicated in some forms of delayed radiation injury, we are investigating whether these compounds can mitigate injury to normal tissues caused by ionizing radiation. This review describes some of this research, focusing on several tissues of therapeutic interest, namely kidney, lung, skin, and oral mucosa. These studies have demonstrated suppression of delayed radiation injury in animals treated with EUK-189 and/or EUK-207. While an antioxidant mechanism of action is postulated, it …

A Rapid And Computationally Inexpensive Method To Virtually Implant Current And Next-Generation Stents Into Subject-Specific Computational Fluid Dynamics Models, Timothy J. Gundert, Shawn C. Shadden, Andrew R. Williams, Bon-Kwon Koo, Jeffrey A. Feinstein, John F. Ladisa

Biomedical Engineering Faculty Research and Publications

Computational modeling is often used to quantify hemodynamic alterations induced by stenting, but frequently uses simplified device or vascular representations. Based on a series of Boolean operations, we developed an efficient and robust method for assessing the influence of current and next-generation stents on local hemodynamics and vascular biomechanics quantified by computational fluid dynamics. Stent designs were parameterized to allow easy control over design features including the number, width and circumferential or longitudinal spacing of struts, as well as the implantation diameter and overall length. The approach allowed stents to be automatically regenerated for rapid analysis of the contribution of …

What Is Inverse-Geometry Ct?, Taly Gilat Schmidt

Biomedical Engineering Faculty Research and Publications

Inverse-geometry computed tomography (IGCT) systems are being developed to provide improved volumetric imaging. In conventional multislice CT systems, x-rays are emitted from a small area and irradiate a large-area detector. In an IGCT system, x-ray sources are distributed over a large area, with each beam irradiating a small-area detector. Therefore, in the inverse geometry, a series of narrow x-ray beams are switched on and off while the gantry rotates. In conventional CT geometry, cone-beam and scatter artifacts increase with the imaged volume thickness. An inverse geometry may be less susceptible to scatter effects, because only a fraction of the field …

Mitochondrial Approaches To Protect Against Cardiac Ischemia And Reperfusion Injury, Amadou K.S. Camara, Martin Bienengraeber, David F. Stowe

Biomedical Engineering Faculty Research and Publications

The mitochondrion is a vital component in cellular energy metabolism and intracellular signaling processes. Mitochondria are involved in a myriad of complex signaling cascades regulating cell death vs. survival. Importantly, mitochondrial dysfunction and the resulting oxidative and nitrosative stress are central in the pathogenesis of numerous human maladies including cardiovascular diseases, neurodegenerative diseases, diabetes, and retinal diseases, many of which are related. This review will examine the emerging understanding of the role of mitochondria in the etiology and progression of cardiovascular diseases and will explore potential therapeutic benefits of targeting the organelle in attenuating the disease process. Indeed, recent advances …

The Dominant Role Of The Hip In Multijoint Reflex Responses In Human Spinal Cord Injury, Tanya Onushko

Dissertations (1934 -)

Following a spinal cord injury (SCI), people often experience exaggerated reflexes, such that mild provocations can cause prolonged and uncontrolled muscle activity throughout the entire leg. These reflexes can be problematic and are known to interfere with functional tasks, such as transferring to and from a wheelchair, and they may interfere with locomotor function by prolonging muscle activity and/or inappropriately activating muscles during attempts to walk. While these multijoint reflexes have been shown to originate from several afferent cues, hip afferent input is a particularly potent sensory signal that readily triggers multijoint reflexes. The overall objective of this dissertation was …

Micro-Ct Characterization Of Human Trabecular Bone In Osteogenesis Imperfecta, John Jameson, Carolyne Albert, Peter Smith, Robert C. Molthen, Gerald F. Harris

Biomedical Engineering Faculty Research and Publications

Osteogenesis imperfecta (OI) is a genetic syndrome affecting collagen synthesis and assembly. Its symptoms vary widely but commonly include bone fragility, reduced stature, and bone deformity. Because of the small size and paucity of human specimens, there is a lack of biomechanical data for OI bone. Most literature has focused on histomorphometric analyses, which rely on assumptions to extrapolate 3-D properties. In this study, a micro-computed tomography (μCT) system was used to directly measure structural and mineral properties in pediatric OI bone collected during routine surgical procedures. Surface renderings suggested a poorly organized, plate-like orientation. Patients with a history of …

Race- And Sex-Related Differences In Retinal Thickness And Foveal Pit Morphology, Melissa Wagner-Schuman, Adam M. Dubis, Rick Nordgren, Yuming Lei, Daniel Odell, Hellen Chiao, Eric Weh, William Fischer, Yusufu N. Sulai, Alfredo Dubra, Joseph Carroll

Biomedical Engineering Faculty Research and Publications

Purpose.

To examine sex- and race-associated differences in macular thickness and foveal pit morphology by using spectral-domain optical coherence tomography (SD-OCT).

Methods.

One hundred eighty eyes of 90 healthy patients (43 women, 47 men) underwent retinal imaging with spectral-domain OCT. The lateral scale of each macular volume scan was corrected for individual differences in axial length by ocular biometry. From these corrected volumes, Early Treatment Diabetic Retinopathy Study (ETDRS) grids of retinal thickness were generated and compared between the groups. Foveal morphology was measured with previously described algorithms.

Results.

Compared with the Caucasians, the Africans and African Americans had reduced …

Energy Deposition In The Breast During Ct Scanning: Quantification And Implications For Dose Reduction, Franco Rupcich, Iacovos Kyprianou, Andreu Badal, Taly Gilat Schmidt

Biomedical Engineering Faculty Research and Publications

Studies suggest that dose to the breast leads to a higher lifetime attributable cancer incidence risk from a chest CT scan for women compared to men. Numerous methods have been proposed for reducing dose to the breast during CT scanning, including bismuth shielding, tube current modulation, partial-angular scanning, and reduced kVp. These methods differ in how they alter the spectrum and fluence across projection angle. This study used Monte Carlo CT simulations of a voxelized female phantom to investigate the energy (dose) deposition in the breast as a function of both photon energy and projection angle. The resulting dose deposition …

Effects Of Acute Rho Kinase Inhibition On Chronic Hypoxia-Induced Changes In Proximal And Distal Pulmonary Arterial Structure And Function, Rebecca R. Vanderpool, Ah Ram Kim, Robert C. Molthen, Naomi Chesler

Biomedical Engineering Faculty Research and Publications

Hypoxic pulmonary hypertension (HPH) is initially a disease of the small pulmonary arteries. Its severity is usually quantified by pulmonary vascular resistance (PVR). Acute Rho kinase inhibition has been found to reduce PVR toward control values in animal models, suggesting that persistent pulmonary vasoconstriction is the dominant mechanism for increased PVR. However, HPH may also cause proximal arterial changes, which are relevant to right ventricular (RV) afterload. RV afterload can be quantified by pulmonary vascular impedance, which is obtained via spectral analysis of pulsatile pressure-flow relationships. To determine the effects of HPH independent of persistent pulmonary vasoconstriction in proximal and …

Multimodality Imaging Of Abnormal Vascular Perfusion And Morphology In Preclinical 9l Gliosarcoma Model, Moses M. Darpolor, Robert C. Molthen, Kathleen M. Schmainda

Biomedical Engineering Faculty Research and Publications

This study demonstrates that a dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) perfusion parameter may indicate vascular abnormality in a brain tumor model and reflects an effect of dexamethasone treatment. In addition, X-ray computed tomography (CT) measurements of vascular tortuosity and tissue markers of vascular morphology were performed to investigate the underpinnings of tumor response to dexamethasone.

Reorganization Of Finger Coordination Patterns During Adaptation To Rotation And Scaling Of A Newly Learned Sensorimotor Transformation, Xiaolin Liu, Kristine M. Mosier, Ferdinando A. Mussa-Ivaldi, Maura Casadio, Robert A. Scheidt

Biomedical Engineering Faculty Research and Publications

We examined how people organize redundant kinematic control variables (finger joint configurations) while learning to make goal-directed movements of a virtual object (a cursor) within a low-dimensional task space (a computer screen). Subjects participated in three experiments performed on separate days. Learning progressed rapidly on day 1, resulting in reduced target capture error and increased cursor trajectory linearity. On days 2 and 3, one group of subjects adapted to a rotation of the nominal map, imposed either stepwise or randomly over trials. Another group experienced a scaling distortion. We report two findings. First, adaptation rates and memory-dependent motor command updating …