Engineering Commons^™

Supernormal Conduction And Suppression Of Spatially Discordant Alternans Of Cardiac Action Potentials, Linyuan Jing, Anuj Agarwal, Abhijit R. Patwardhan

Biomedical Engineering Faculty Publications

Spatially discordant alternans (DA) of action potential durations (APD) is thought to be more pro-arrhythmic than concordant alternans. Super normal conduction (SNC) has been reported to suppress formation of DA. An increase in conduction velocity (CV) as activation rate increases, i.e., a negative CV restitution, is widely considered as hallmark of SNC. Our aim in this study is to show that it is not an increase in CV for faster rates that prevents formation of DA, rather, it is the ratio of the CV for the short relative to the long activation that is critical in DA suppression. To illustrate …

Recent Advances In Optical Spectroscopic And Imaging Methods For Medicine And Biology, Yu Shang, Zhiyu Qian, Rickson C. Mesquita, Mathieu Dehaes

Biomedical Engineering Faculty Publications

No abstract provided.

2d Cine Dense With Low Encoding Frequencies Accurately Quantifies Cardiac Mechanics With Improved Image Characteristics, Gregory J. Wehner, Jonathan D. Grabau, Jonathan D. Suever, Christopher M. Haggerty, Linyuan Jing, David Powell, Sean M. Hamlet, Moriel H. Vandsburger, Xiaodong Zhong, Brandon K. Fornwalt

Biomedical Engineering Faculty Publications

BACKGROUND: Displacement Encoding with Stimulated Echoes (DENSE) encodes displacement into the phase of the magnetic resonance signal. The encoding frequency (k_e) maps the measured phase to tissue displacement while the strength of the encoding gradients affects image quality. 2D cine DENSE studies have used a k_e of 0.10 cycles/mm, which is high enough to remove an artifact-generating echo from k-space, provide high sensitivity to tissue displacements, and dephase the blood pool. However, through-plane dephasing can remove the unwanted echo and dephase the blood pool without relying on high k_e. Additionally, the high sensitivity comes …

Noncontact Diffuse Correlation Tomography Of Human Breast Tumor, Lian He, Yu Lin, Chong Huang, Daniel Irwin, Margaret M. Szabunio, Guoqiang Yu

Biomedical Engineering Faculty Publications

Our first step to adapt our recently developed noncontact diffuse correlation tomography (ncDCT) system for three-dimensional (3-D) imaging of blood flow distribution in human breast tumors is reported. A commercial 3-D camera was used to obtain breast surface geometry, which was then converted to a solid volume mesh. An ncDCT probe scanned over a region of interest on the mesh surface and the measured boundary data were combined with a finite element framework for 3-D image reconstruction of blood flow distribution. This technique was tested in computer simulations and in vivo human breasts with low-grade carcinoma. Results from computer simulations …

Noncontact Diffuse Optical Assessment Of Blood Flow Changes In Head And Neck Free Tissue Transfer Flaps, Chong Huang, Yu Lin, Yu Shang, Guoqiang Yu, Jeffrey Radabaugh, Rony Aouad, Thomas J. Gal, Amit B. Patel, Joseph Valentino

Biomedical Engineering Faculty Publications

Knowledge of tissue blood flow (BF) changes after free tissue transfer may enable surgeons to predict the failure of flap thrombosis at an early stage. This study used our recently developed noncontact diffuse correlation spectroscopy to monitor dynamic BF changes in free flaps without getting in contact with the targeted tissue. Eight free flaps were elevated in patients with head and neck cancer; one of the flaps failed. Multiple BF measurements probing the transferred tissue were performed during and post the surgical operation. Postoperative BF values were normalized to the intraoperative baselines (assigning “1”) for the calculation of relative BF …

Effects Of Individualized Centrifugation Training On Orthostatic Tolerance In Men And Women, Nandu Goswami, Joyce Evans, Stefan Schneider, Melanie Von Der Wiesche, Edwin Mulder, Andreas Rössler, Helmut Hinghofer-Szalkay, Andrew P. Blaber

Biomedical Engineering Faculty Publications

AIMS: Exposure to artificial gravity (AG) at different G loads and durations on human centrifuges has been shown to improve orthostatic tolerance in men. However, the effects on women and of an individual-specific AG training protocol on tolerance are not known.

METHODS: We examined the effects of 90 minutes of AG vs. 90 minutes of supine rest on the orthostatic tolerance limit (OTL), using head up tilt and lower body negative pressure until presyncope of 7 men and 5 women. Subjects were placed in the centrifuge nacelle while instrumented and after one-hour they underwent either: 1) AG exposure …

Treating Proximal Tibial Growth Plate Injuries Using Poly(Lactic-Co-Glycolic Acid) Scaffolds, Amanda Clark, J. Zach Hilt, Todd A. Milbrandt, David A. Puleo

Biomedical Engineering Faculty Publications

Growth plate fractures account for nearly 18.5% of fractures in children. Depending on the type and severity of the injury, inhibited bone growth or angular deformity caused by bone forming in place of the growth plate can occur. The current treatment involves removal of the bony bar and replacing it with a filler substance, such as a free fat graft. Unfortunately, reformation of the bony bar frequently occurs, preventing the native growth plate from regenerating. The goal of this pilot study was to determine whether biodegradable scaffolds can enhance native growth plate regeneration following a simulated injury that resulted in …

A NTh-Order Linear Algorithm For Extracting Diffuse Correlation Spectroscopy Blood Flow Indices In Heterogeneous Tissues, Yu Shang, Guoqiang Yu

Biomedical Engineering Faculty Publications

Conventional semi-infinite analytical solutions of correlation diffusion equation may lead to errors when calculating blood flow index (BFI) from diffuse correlation spectroscopy (DCS) measurements in tissues with irregular geometries. Very recently, we created an algorithm integrating a Nth-order linear model of autocorrelation function with the Monte Carlo simulation of photon migrations in homogenous tissues with arbitrary geometries for extraction of BFI (i.e., αD_B ). The purpose of this study is to extend the capability of the Nth-order linear algorithm for extracting BFI in heterogeneous tissues with arbitrary geometries. The previous linear algorithm was modified to extract BFIs …

Diffuse Correlation Spectroscopy (Dcs) For Assessment Of Tissue Blood Flow In Skeletal Muscle: Recent Progress, Yu Shang, Katelyn Gurley, Guoqiang Yu

Biomedical Engineering Faculty Publications

Near-infrared diffuse correlation spectroscopy (DCS) is an emerging technology for monitoring blood flow in various tissues. This article reviews the recent progress of DCS for the assessment of skeletal muscle blood flow, including the developments in technology allowing use during dynamic exercise and muscular electrical stimulation, the utilization for diagnosis of muscle vascular diseases, and the applications for evaluating treatment effects. The limitations of current DCS studies and future perspective are finally discussed.

Simultaneous Measurement Of Deep Tissue Blood Flow And Oxygenation Using Noncontact Diffuse Correlation Spectroscopy Flow-Oximeter, Ting Li, Yu Lin, Yu Shang, Lian He, Chong Huang, Margaret M. Szabunio, Guoqiang Yu

Biomedical Engineering Faculty Publications

We report a novel noncontact diffuse correlation spectroscopy flow-oximeter for simultaneous quantification of relative changes in tissue blood flow (rBF) and oxygenation (Δ[oxygenation]). The noncontact probe was compared against a contact probe in tissue-like phantoms and forearm muscles (n = 10), and the dynamic trends in both rBF and Δ[oxygenation] were found to be highly correlated. However, the magnitudes of Δ[oxygenation] measured by the two probes were significantly different. Monte Carlo simulations and phantom experiments revealed that the arm curvature resulted in a significant underestimation (~-20%) for the noncontact measurements in Δ[ …

Load-Relaxation Properties Of The Human Trunk In Response To Prolonged Flexion: Measuring And Modeling The Effect Of Flexion Angle, Nima Toosizadeh, Maury A. Nussbaum, Babak Bazrgari, Michael L. Madigan

Biomedical Engineering Faculty Publications

Experimental studies suggest that prolonged trunk flexion reduces passive support of the spine. To understand alterations of the synergy between active and passive tissues following such loadings, several studies have assessed the time-dependent behavior of passive tissues including those within spinal motion segments and muscles. Yet, there remain limitations regarding load-relaxation of the lumbar spine in response to flexion exposures and the influence of different flexion angles. Ten healthy participants were exposed for 16 min to each of five magnitudes of lumbar flexion specified relative to individual flexion-relaxation angles (i.e., 30, 40, 60, 80, and 100%), during which lumbar flexion …

Noninvasive Optical Characterization Of Muscle Blood Flow, Oxygenation, And Metabolism In Women With Fibromyalgia, Yu Shang, Katelyn Gurley, Brock Symons, Douglas Long, Ratchakrit Srikuea, Leslie J. Crofford, Charlotte A. Peterson, Guoqiang Yu

Biomedical Engineering Faculty Publications

INTRODUCTION: Women with fibromyalgia (FM) have symptoms of increased muscular fatigue and reduced exercise tolerance, which may be associated with alterations in muscle microcirculation and oxygen metabolism. This study used near-infrared diffuse optical spectroscopies to noninvasively evaluate muscle blood flow, blood oxygenation and oxygen metabolism during leg fatiguing exercise and during arm arterial cuff occlusion in post-menopausal women with and without FM.

METHODS: Fourteen women with FM and twenty-three well-matched healthy controls participated in this study. For the fatiguing exercise protocol, the subject was instructed to perform 6 sets of 12 isometric contractions of knee extensor muscles with intensity steadily …

Noninvasive Optical Quantification Of Absolute Blood Flow, Blood Oxygenation, And Oxygen Consumption Rate In Exercising Skeletal Muscle, Katelyn Gurley, Yu Shang, Guoqiang Yu

Biomedical Engineering Faculty Publications

This study investigates a method using novel hybrid diffuse optical spectroscopies [near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS)] to obtain continuous, noninvasive measurement of absolute blood flow (BF), blood oxygenation, and oxygen consumption rate (V̇O₂) in exercising skeletal muscle. Healthy subjects (n=9) performed a handgrip exercise to increase BF and V̇O₂ in forearm flexor muscles, while a hybrid optical probe on the skin surface directly monitored oxy-, deoxy-, and total hemoglobin concentrations ([HbO₂], [Hb], and THC), tissue oxygen saturation (S_tO₂), relative BF (rBF), and relative oxygen …