Biomedical Engineering and Bioengineering Commons^™

Quasi-Exact Helical Cone Beam Reconstruction For Micro Ct, Jicun Hu, Robert C. Molthen, Roger Johnson, Steven Haworth, Christopher Dawson

Biomedical Engineering Faculty Research and Publications

A cone beam micro-CT system is set up to collect truncated helical cone beam data. This system includes a micro-focal X-ray source, a precision computer-controlled X-Y-Z-theta stage, and an image-intensifier coupled to a large format CCD detector. The helical scanning mode is implemented by rotating and translating the stage while keeping X-ray source and detector stationary. A chunk of bone and a mouse leg are scanned and quasi-exact reconstruction is performed using the approach proposed in J. Hu et al. (2001). This approach introduced the original idea of accessory paths with upper and lower virtual detectors having infinite axial extent. …

A Pneumatically Actuated Manipulandum For Neuromotor Control Research, Aaron J Suminski, Kristina M. Ropella, Robert A. Scheidt

Biomedical Engineering Faculty Research and Publications

Functional magnetic resonance imaging (fMRI) techniques have great potential for identifying which neural structures are involved in the control of goal-directed reaching movements. However, fMRI techniques alone are not capable of probing the neural mechanisms involved in acquisition of novel motor behaviors because such studies require that the moving limb be perturbed in a controlled fashion. We outline a plan to design and develop a non-metallic, pneumatically actuated tool that, along with systems identification techniques and functional magnetic resonance imaging (fMRI), will characterize and quantify how the human central nervous system uses sensory information during practice-based motor learning.

Pulmonary Arterial Morphometry From Microfocal X-Ray Computed Tomography, Kelly L. Karau, Robert C. Molthen, Anita H. Dhyani, Steven Thomas Haworth, Christopher C. Hanger, David L. Roerig, Roger H. Johnson, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

The objective of this study was to develop an X-ray computed tomographic method for pulmonary arterial morphometry. The lungs were removed from a rat, and the pulmonary arterial tree was filled with perfluorooctyl bromide to enhance X-ray absorbance. At each of four pulmonary arterial pressures (30, 21, 12, and 5.4 mmHg), the lungs were rotated within the cone of the X-ray beam that was projected from a microfocal X-ray source onto an image intensifier, and 360 images were obtained at 1° increments. The three-dimensional image volumes were reconstructed with isotropic resolution with the use of a cone beam reconstruction algorithm. …

Microfocal X-Ray Ct Imaging And Pulmonary Arterial Distensibility In Excised Rat Lungs, Kelly L. Karau, Roger H. Johnson, Robert C. Molthen, Anita H. Dhyani, Steven Thomas Haworth, Christopher C. Hanger, David L. Roerig, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

The objective of this study was to develop an X-ray computed tomographic method for measuring pulmonary arterial dimensions and locations within the intact rat lung. Lungs were removed from rats and their pulmonary arterial trees were filled with perfluorooctyl bromide to enhance X-ray absorbance. The lungs were rotated within the cone of the X-ray beam projected from a microfocal X-ray source onto an image intensifier, and 360 images were obtained at 1° increments. The three-dimensional image volumes were reconstructed with isotropic resolution using a cone beam reconstruction algorithm. The vessel diameters were obtained by fitting a functional form to the …

Learning To Move Amid Uncertainty, Robert A. Scheidt, Jonathan B. Dingwell, Ferdinando A. Mussa-Ivaldi

Biomedical Engineering Faculty Research and Publications

We studied how subjects learned to make movements against unpredictable perturbations. Twelve healthy human subjects made goal-directed reaching movements in the horizontal plane while holding the handle of a two-joint robotic manipulator. The robot generated viscous force fields that perturbed the limb perpendicular to the desired direction of movement. The amplitude (but not the direction) of the viscous field varied randomly from trial to trial. Systems identification techniques were employed to characterize how subjects adapted to these random perturbations. Subject performance was quantified primarily using the peak deviation from a straight-line hand path. Subjects adapted their arm movements to the …

Semiautomated Skeletonization Of The Pulmonary Arterial Tree In Micro-Ct Images, Christopher C. Hanger, Steven Thomas Haworth, Robert C. Molthen, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

We present a simple and robust approach that utilizes planar images at different angular rotations combined with unfiltered back-projection to locate the central axes of the pulmonary arterial tree. Three-dimensional points are selected interactively by the user. The computer calculates a sub- volume unfiltered back-projection orthogonal to the vector connecting the two points and centered on the first point. Because more x-rays are absorbed at the thickest portion of the vessel, in the unfiltered back-projection, the darkest pixel is assumed to be the center of the vessel. The computer replaces this point with the newly computer-calculated point. A second back-projection …

Pulmonary Arterial Remodeling Revealed By Microfocal X-Ray Tomography, Kelly L. Karau, Robert C. Molthen, Anita H. Dhyani, Steven Thomas Haworth, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

Animal models and micro-CT imaging are useful for understanding the functional consequences of, and identifying the genes involved in, the remodeling of vascular structures that accompanies pulmonary vascular disease. Using a micro-CT scanner to image contrast-enhanced arteries in excised lungs from fawn hooded rats (a strain genetically susceptible to hypoxia induced pulmonary hypertension), we found that portions of the pulmonary arterial tree downstream from a given diameter were morphometrically indistinguishable. This 'self-consistency' property provided a means for summarizing the pulmonary arterial tree architecture and mechanical properties using a parameter vector obtained from measurements of the contiguous set of vessel segments …

Direct Current Electrical Stimulation Increases The Fusion Rate Of Spinal Fusion Cages, Jeffrey M. Toth, Howard Seim, Jeffrey D. Schwardt, Wendy B. Humphrey, Joel A. Wallskog, A. Simon Turner

Biomedical Engineering Faculty Research and Publications

Study Design. A randomized experimental evaluation of direct current stimulation in a validated animal model with an experimental control group, using blinded radiographic, biomechanical, histologic, and statistical measures.

Objectives. To evaluate the efficacy of the adjunctive use of direct current stimulation on the fusion rate and speed of healing of titanium interbody fusion cages packed with autograft in a sheep lumbar interbody fusion model.

Summary of Background Data. Titanium lumbar interbody spinal fusion cages have been reported to be 90% effective for single-level lumbar interbody fusion. However, fusion rates are reported to be between 70% and 80% in patients with …

Persistence Of Motor Adaptation During Constrained, Multi-Joint, Arm Movements, Robert A. Scheidt, David J. Reinkensmeyer, Michael A. Conditt, W. Zev Reymer, Ferdinando A. Mussa-Ivaldi

Biomedical Engineering Faculty Research and Publications

We studied the stability of changes in motor performance associated with adaptation to a novel dynamic environment during goal-directed movements of the dominant arm. Eleven normal, human subjects made targeted reaching movements in the horizontal plane while holding the handle of a two-joint robotic manipulator. This robot was programmed to generate a novel viscous force field that perturbed the limb perpendicular to the desired direction of movement. Following adaptation to this force field, we sought to determine the relative role of kinematic errors and dynamic criteria in promoting recovery from the adapted state. In particular, we compared kinematic and dynamic …

Micro-Ct Image-Derived Metrics Quantify Arterial Wall Distensibility Reduction In A Rat Model Of Pulmonary Hypertension, Roger H. Johnson, Kelly L. Karau, Robert C. Molthen, Steven Thomas Haworth, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

We developed methods to quantify arterial structural and mechanical properties in excised rat lungs and applied them to investigate the distensibility decrease accompanying chronic hypoxia-induced pulmonary hypertension. Lungs of control and hypertensive (three weeks 11% O₂) animals were excised and a contrast agent introduced before micro-CT imaging with a special purpose scanner. For each lung, four 3D image data sets were obtained, each at a different intra-arterial contrast agent pressure. Vessel segment diameters and lengths were measured at all levels in the arterial tree hierarchy, and these data used to generate features sensitive to distensibility changes. Results indicate …

Control Strategies For The Transition From Multijoint To Single-Joint Arm Movements Studied Using A Simple Mechanical Constraint, Robert A. Scheidt, W. Zev Rymer

Biomedical Engineering Faculty Research and Publications

Changes were studied in neuromotor control that were evoked by constraining the motion of the elbow joint during planar, supported movements of the dominant arm in eight normal human subjects. Electromyograph (EMG) recordings from shoulder and arm muscles were used to determine whether the normal multijoint muscle activity patterns associated with reaching to a visual target were modified when the movement was reduced to a single-joint task, by pinning the elbow to a particular location in the planar work space. Three blocks of 150 movements each were used in the experiments. Subjects were presented with the unconstrained task in the …

3d Micro-Ct For Functional Genomics, R. H. Johnson, Robert C. Molthen, Christopher C. Hanger, Kelly Lynn Karau, Steven Haworth, Christopher Dawson

Biomedical Engineering Faculty Research and Publications

No abstract provided.

Quantification Of Pulmonary Arterial Wall Distensibility Using Parameters Extracted From Volumetric Micro-Ct Images, Roger H. Johnson, Kelly Lynn Karau, Robert C. Molthen, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

Stiffening, or loss of distensibility, of arterial vessel walls is among the manifestations of a number of vascular diseases including pulmonary arterial hypertension. We are attempting to quantify the mechanical properties of vessel walls of the pulmonary arterial tree using parameters derived from high-resolution volumetric x-ray CT images of rat lungs. The pulmonary arterial trees of the excised lungs are filled with a contrast agent. The lungs are imaged with arterial pressures spanning the physiological range. Vessel segment diameters are measured from the inlet to the periphery, and distensibilities calculated from diameters as a function of pressure. The method shows …

Anatomy Of Soft Tissues Of The Spinal Canal, Hogan Quinn, Jeffrey M. Toth

Biomedical Engineering Faculty Research and Publications

Background and Objectives.

Important issues regarding the spread of solutions in the epidural space and the anatomy of the site of action of spinal and epidural injections are unresolved. However, the detailed anatomy of the spinal canal has been incompletely determined. We therefore examined the microscopic anatomy of the spinal canal soft tissues, including relationships to the canal walls.

Methods.

Whole mounts were prepared of decalcified vertebral columns with undisturbed contents from three adult humans. Similar material was prepared from a macaque and baboon immediately on death to control for artifact of tissue change after death. Other tissues examined included …

Detection Of Changes In Lung Tissue Properties With Multiple-Indicator Dilution, David L. Roerig, Said H. Audi, John H. Linehan, Gary S. Krenz, S. B. Ahlf, W. Lin, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

We evaluated the potential utility of a group of indicators, each of which targets a particular tissue property, as indicators in the multiple-indicator dilution method to detect and to identify abnormalities in lung tissue properties resulting from lung injury models. We measured the pulmonary venous outflow concentration vs. time curves of [¹⁴C]diazepam, ³HOH, [¹⁴C]phenylethylamine, and a vascular reference indicator following their bolus injection into the pulmonary artery of isolated perfused rabbit lungs under different experimental conditions, resulting in changes in the lung tissue composition. The conditions included granulomatous inflammation, induced by the intravenous injection of …

The Use Of Recombinant Human Bone Morphogenetic Protein 2 (Rhbmp-2) To Promote Spinal Fusion In A Nonhuman Primate Anterior Interbody Fusion Model, Brian P. Hecht, Jeffrey S. Fischgrund, Harry N. Harkowitz, Lori Penman, Jeffrey M. Toth, Ali Shirkhoda

Biomedical Engineering Faculty Research and Publications

Study Design. A study on the efficacy of recombinant human bone morphogenetic protein 2 (rhBMP-2) in a nonhuman primate anterior interbody fusion model.

Objectives. To investigate the efficacy of rhBMP-2 with an absorbable collagen sponge carrier to promote spinal fusion in a nonhuman primate anterior interbody fusion model.

Summary of Background Data. RhBMP-2 is an osteoinductive growth factor capable of inducing new bone formation in vivo. Although dosage studies using rhBMP-2 have been performed on species of lower phylogenetic level, they cannot be extrapolated to the primate. Dosage studies on nonhuman primates are essential before proceeding with human primate application. …

An Iterative Approach To The Beam Hardening Correction In Cone Beam Ct (Proceedings), Jiang Hsieh, Robert C. Molthen, Christopher A. Dawson, Roger H. Johnson

Biomedical Engineering Faculty Research and Publications

No abstract provided.

Efficacy Of Beam-Hardening Correction For Vascular Morphometry Using 3d Conebeam Micro-Ct, Roger H. Johnson, Jiang Hsieh, Robert C. Molthen, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

No abstract provided.

Pulmonary Disposition Of Lipophilic Amine Compounds In The Isolated Perfused Rabbit Lung, Said H. Audi, Christopher A. Dawson, John H. Linehan, Gary S. Krenz, S. B. Ahlf, David L. Roerig

Biomedical Engineering Faculty Research and Publications

We measured the pulmonary venous concentration vs. time curves for [³H]alfentanil, [¹⁴C]lidocaine, and [³H]codeine after the bolus injection of each of these lipophilic amine compounds (LAC) and a vascular-reference indicator (fluorescein isothiocyanate-dextran) into the pulmonary artery of isolated perfused rabbit lungs. A range of flows and perfusate albumin concentrations was studied. To evaluate the information content of the data, we developed a kinetic model describing the pulmonary disposition of these LAC that was based on indicator dilution theory, and we sought a robust approach for interpreting the estimated model parameters. We found that the …

Sensory Changes In Adults With Unilateral Transtibial Amputation, Judith B. Kosasih, Barbara Silver-Thorn

Biomedical Engineering Faculty Research and Publications

The purpose of this study was to describe the sensory changes in adults with unilateral transtibial amputation

(TTA), as any loss of sensation may have significant impact on the successful use of a prosthesis. Sensory modalities of light touch, deep pressure, vibration, and superficial pain (pinprick) were examined on the residual and contralateral limbs of 16 veterans with TTA. Six subjects demonstrated normal sensation on the contralateral limb and impaired sensation of superficial pain, vibration, and/or light touch on the residual limb. Superficial pain was the most frequently impaired sensation, and vibration and superficial pain sensation appeared to be age-dependent, …

Water Transport And The Distribution Of Aquaporin-1 In Pulmonary Air Spaces, Richard M. Effros, C. Darin, Elizabeth R. Jacobs, R. A. Rogers, Gary S. Krenz, E. E. Schneeberger

Biomedical Engineering Faculty Research and Publications

Recent evidence suggests that water transport between the pulmonary vasculature and air spaces can be inhibited by HgCl₂, an agent that inhibits water channels (aquaporin-1 and -5) of cell membranes. In the present study of isolated rat lungs, clearances of labeled (³HOH) and unlabeled water were compared after instillation of hypotonic or hypertonic solutions into the air spaces or injection of a hypotonic bolus into the pulmonary artery. The clearance of ³HOH between the air spaces and perfusate after intratracheal instillation and from the vasculature to the tissues after pulmonary arterial injections was invariably greater …

Laparoscopic Assisted Fusion Of The Lumbosacral Spine: A Biomechanical And Histologic Analysis Of The Open Versus Laparoscopic Technique In An Animal Model, Lee H. Riley Iii, Jason C. Eck, Hiryuki Yoshida, Jeffrey M. Toth, Nguyen Cahn, Tae Hong Lim, Linda M. Mcgrady

Biomedical Engineering Faculty Research and Publications

Study Design. An animal model for laparoscopic lumbosacral fusion.

Objectives. To compare the biomechanical and histologic results of open to laparoscopic lumbosacral discectomy and fusion in an animal model.

Background Data. Early clinical reports of laparoscopic lumbosacral fusions are encouraging, but animal experiments have not been reported.

Methods. Ten pigs (50-80 kg) were divided into two groups. Group 1 underwent an open anterior lumbosacral discectomy and fusion at L7-S1 using autologous bone graft and a titanium MOSS (DePuy Motech) cage. Group 2 was identical to Group 1 except that a laparoscopic technique was used. The animals were killed at 3 …

Experimental Spinal Fusion With Recombinant Human Bone Morphogenetic Protein-2 Without Decortication Of Osseous Elements, Harvinder Sandhu, Linda E.A. Kanim, Jeffrey M. Toth, J. Michael Kabo, David Liu, Rick B. Delamarter, Edgar G. Dawson

Biomedical Engineering Faculty Research and Publications

Study Design. L4-L5 intertransverse process fusions were produced with 58 μg, 230 μg, or 920 μg of recombinant human bone morphogenetic protein-2 in 20 dogs. Eleven had traditional decortication of posterior elements before insertion of the implant. Nine were left undecorticated. All animals were evaluated 3 months after surgery.

Objectives. To determine whether decortication is a prerequisite for successful fusion in the presence of osteoinductive proteins such as bone morphogenetic protein-2.

Summary of Background Data. Recombinant osteoinductive proteins can induce de novo bone in ectopic soft-tissue sites in the absence of bone marrow elements. Traditional methods for achieving spinal fusion …

Generic, Geometric Finite Element Analysis Of The Transtibial Residual Limb And Prosthetic Socket, Barbara Silver-Thorn, Dudley S. Childress

Biomedical Engineering Faculty Research and Publications

Finite element analysis was used to investigate the stress distribution between the residual limb and prosthetic socket of persons with transtibial amputation (TTA). The purpose of this study was to develop a tool to provide a quantitative estimate of prosthetic interface pressures to improve our understanding of residual limb/prosthetic socket biomechanics and prosthetic fit. FE models of the residual limb and prosthetic socket were created. In contrast to previous FE models of the prosthetic socket/residual limb system, these models were not based on the geometry of a particular individual, but instead were based on a generic, geometric approximation of the …

Effective Doses Of Recombinant Human Bone Morphogenetic Protein-2 In Experimental Spinal Fusion, Harvinder Sandhu, Linda E.A. Kanim, J. Michael Kabo, Jeffrey M. Toth, Erik N. Zeegen, David Liu, Rick B. Delamarter, Edgar G. Dawson

Biomedical Engineering Faculty Research and Publications

Study Design

Nineteen dogs underwent L4-L5 intertransverse process fusions with either 58 μg, 115 μg, 230 μg, 460 μg, or 920 μg of recombinant human bone morphogenetic protein-2 carried by a polylactic acid polymer. A previous study (12 dogs) compared 2300 μg of recombinant human bone morphogenetic protein-2, autogenous iliac bone, and carrier alone in this model. All fusions subsequently were compared.

Objectives

To characterize the dose-response relationship of recombinant human bone morphogenetic protein-2 in a spinal fusion model.

Summary of Background Data

Recombinant osteoinductive morphogens, such as recombinant human bone morphogenetic protein-2, are effective in vertebrate diaphyseal defect and …

Parametric Analysis Using The Finite Element Method To Investigate Prosthetic Interface Stresses For Persons With Trans-Tibial Amputation, Barbara Silver-Thorn, Dudley S. Childress

Biomedical Engineering Faculty Research and Publications

A finite element (FE) model of the below-knee residual limb and prosthetic socket was created to investigate the effects of parameter variations on the interface stress distribution during static stance. This model was based upon geometric approximations of anthropometric residual limb geometry. The model was not specific to an individual with amputation, but could be scaled to approximate the limb of a particular subject. Parametric analyses were conducted to investigate the effects of prosthetic socket design and residual limb geometry on the residual limb/prosthetic socket interface stresses. Behavioral trends were illustrated via sensitivity analysis.

The results of the parametric analyses …

A Review Of Prosthetic Interface Stress Investigations, Barbara Silver-Thorn, John W. Steege, Dudley S. Childress

Biomedical Engineering Faculty Research and Publications

Over the last decade, numerous experimental and numerical analyses have been conducted to investigate the stress distribution between the residual limb and prosthetic socket of persons with lower limb amputation. The objectives of these analyses have been to improve our understanding of the residual limb/prosthetic socket system, to evaluate the influence of prosthetic design parameters and alignment variations on the interface stress distribution, and to evaluate prosthetic fit. The purpose of this paper is to summarize these experimental investigations and identify associated limitations. In addition, this paper presents an overview of various computer models used to investigate the residual limb …

Estimation Of The Pulmonary Capillary Transport Function In Isolated Rabbit Lungs., Said H. Audi, J H. Linehan, Gary S. Krenz, C A. Dawson, S B. Ahlf, David L. Roerig

Biomedical Engineering Faculty Research and Publications

Recently, we presented a method for estimating the pulmonary capillary volume and transport function based on the use of a reference indicator and two or more indicators that rapidly equilibrate (radially) with the tissue (i.e., the concentrations in the vascular and extravascular spaces at a given axial location are in equilibrium) during transit through the capillaries in a bolus-injection indicator dilution method (S. H. Audi, G. S. Krenz, J. H. Linehan, D. A. Rickaby, and C. A. Dawson. J. Appl. Physiol. 77: 332-351, 1994). The objectives of the present study were 1) to determine whether [¹⁴C]diazepam …

Non‐Rayleigh Statistics Of Ultrasonic Backscattered Echo From Tissues, V. Manjo Narayanan, Robert C. Molthen, P. M. Shankar, J. M. Reid

Biomedical Engineering Faculty Research and Publications

The envelope of the backscattered signal from tissues can exhibit non‐Rayleigh statistics if the number density of scatterers is small or if the variations in the scattering cross sections are random. The K distribution which has been used extensively in radar, is introduced to model this non‐Rayleigh behavior. The generalized K distribution is extremely useful since it encompasses a wide range of distributions such as Rayleigh, Lognormal, and Rician. Computer simulations were conducted using a simple one‐dimensional discrete scatteringmodel to investigate the properties of the echo envelope. In addition to cases of low number densities, significant departures from Rayleigh statistics …

Instrumentation And Control For A Microprocessor-Based Coronary Perfusion System, Daniel L. Priester

Master's Theses (1922-2009) Access restricted to Marquette Campus

No abstract provided.