Digital Commons Network^™

Identifying Canonical And Replicable Multi-Scale Intrinsic Connectivity Networks In 100k+ Resting-State Fmri Datasets., A Iraji, Z Fu, A Faghiri, M Duda, J Chen, S Rachakonda, T Deramus, P Kochunov, B M Adhikari, A Belger, J M Ford, D H Mathalon, G D Pearlson, S G Potkin, A Preda, J A Turner, T G M Van Erp, J R Bustillo, K Yang, K Ishizuka, A Faria, A Sawa, K Hutchison, E A Osuch, Jean Theberge, C Abbott, B A Mueller, D Zhi, C Zhuo, S Liu, Y Xu, M Salman, J Liu, Y Du, J Sui, T Adali, V D Calhoun

Department of Medicine Publications

Despite the known benefits of data-driven approaches, the lack of approaches for identifying functional neuroimaging patterns that capture both individual variations and inter-subject correspondence limits the clinical utility of rsfMRI and its application to single-subject analyses. Here, using rsfMRI data from over 100k individuals across private and public datasets, we identify replicable multi-spatial-scale canonical intrinsic connectivity network (ICN) templates via the use of multi-model-order independent component analysis (ICA). We also study the feasibility of estimating subject-specific ICNs via spatially constrained ICA. The results show that the subject-level ICN estimations vary as a function of the ICN itself, the data length, …

Neuroimaging-Based Classification Of Ptsd Using Data-Driven Computational Approaches: A Multisite Big Data Study From The Enigma-Pgc Ptsd Consortium., Xi Zhu, Yoojean Kim, Orren Ravid, Xiaofu He, Benjamin Suarez-Jimenez, Sigal Zilcha-Mano, Amit Lazarov, Seonjoo Lee, Chadi G Abdallah, Michael Angstadt, Christopher L Averill, C Lexi Baird, Lee A Baugh, Jennifer U Blackford, Jessica Bomyea, Steven E Bruce, Richard A Bryant, Zhihong Cao, Kyle Choi, Josh Cisler, Andrew S Cotton, Judith K Daniels, Nicholas D Davenport, Richard J Davidson, Michael D Debellis, Emily L Dennis, Maria Densmore, Terri Deroon-Cassini, Seth G Disner, Wissam El Hage, Amit Etkin, Negar Fani, Kelene A Fercho, Jacklynn Fitzgerald, Gina L Forster, Jessie L Frijling, Elbert Geuze, Atilla Gonenc, Evan M Gordon, Staci Gruber, Daniel W Grupe, Jeffrey P Guenette, Courtney C Haswell, Ryan J Herringa, Julia Herzog, David Bernd Hofmann, Bobak Hosseini, Anna R Hudson, Ashley A Huggins, Jonathan C Ipser, Neda Jahanshad, Meilin Jia-Richards, Tanja Jovanovic, Milissa L Kaufman, Mitzy Kennis, Anthony King, Philipp Kinzel, Saskia B J Koch, Inga K Koerte, Sheri M Koopowitz, Mayuresh S Korgaonkar, John H Krystal, Ruth Lanius, Christine L Larson, Lauren A M Lebois, Gen Li, Israel Liberzon, Guang Ming Lu, Yifeng Luo, Vincent A Magnotta, Antje Manthey, Adi Maron-Katz, Geoffery May, Katie Mclaughlin, Sven C Mueller, Laura Nawijn, Steven M Nelson, Richard W J Neufeld, Jack B Nitschke, Erin M O'Leary, Bunmi O Olatunji, Miranda Olff, Matthew Peverill, K Luan Phan, Rongfeng Qi, Yann Quidé, Ivan Rektor, Kerry Ressler, Pavel Riha, Marisa Ross, Isabelle M Rosso, Lauren E Salminen, Kelly Sambrook, Christian Schmahl, Martha E Shenton, Margaret Sheridan, Chiahao Shih, Maurizio Sicorello, Anika Sierk, Alan N Simmons, Raluca M Simons, Jeffrey S Simons, Scott R Sponheim, Murray B Stein, Dan J Stein, Jennifer S Stevens, Thomas Straube, Delin Sun, Jean Theberge, Paul M Thompson, Sophia I Thomopoulos, Nic J A Van Der Wee, Steven J A Van Der Werff, Theo G M Van Erp, Sanne J H Van Rooij, Mirjam Van Zuiden, Tim Varkevisser, Dick J Veltman, Robert R J M Vermeiren, Henrik Walter, Li Wang, Xin Wang, Carissa Weis, Sherry Winternitz, Hong Xie, Ye Zhu, Melanie Wall, Yuval Neria, Rajendra A Morey

Department of Medicine Publications

BACKGROUND: Recent advances in data-driven computational approaches have been helpful in devising tools to objectively diagnose psychiatric disorders. However, current machine learning studies limited to small homogeneous samples, different methodologies, and different imaging collection protocols, limit the ability to directly compare and generalize their results. Here we aimed to classify individuals with PTSD versus controls and assess the generalizability using a large heterogeneous brain datasets from the ENIGMA-PGC PTSD Working group.

METHODS: We analyzed brain MRI data from 3,477 structural-MRI; 2,495 resting state-fMRI; and 1,952 diffusion-MRI. First, we identified the brain features that best distinguish individuals with PTSD from controls …

In Vivo Multi-Modal Imaging Approaches For Cancer, Stem And Immune Cells, Nourhan Shalaby

Electronic Thesis and Dissertation Repository

Introduction: Molecular imaging allows for non-invasive longitudinal visualization of cellular functions in vivo. This area of research has provided better understanding of fundamental molecular and biochemical processes, enabled optimization of pre-clinical and clinical assessments for new treatments, and allowed for more accurate and early detection of many pathologies. Extensive research for novel imaging techniques and emerging technologies have rapidly advanced the field. However, an ideal single imaging modality or approach does not exist. Alternatively, multi-modal imaging approaches are commonly applied to overcome limitations of individual technologies. In this thesis, we design, develop, validate, and image various cell types using …

Building A Magnetosome-Like Nanoparticle For Magnetic Resonance Imaging, Qin Sun

Electronic Thesis and Dissertation Repository

With its superb spatial and temporal resolution, magnetic resonance imaging (MRI) has great potential to track cellular activities that define early stages of disease. To improve molecular imaging techniques, we are developing MRI reporter gene expression based on the magnetosome. In magnetotactic bacteria (MTB), magnetosome formation compartmentalizes iron biominerals in membrane-enclosed vesicles. We hypothesize that essential magnetosome proteins interact in any cell type to form rudimentary magnetosome-like nanoparticles, providing a genetically-controlled contrast agent for molecular MRI.

MTB genes mamE, mamB, mamI, and mamL were cloned from M. magneticum sp. AMB-1 genomic DNA by PCR and inserted into …

Novel 129xe Magnetic Resonance Imaging And Spectroscopy Measurements Of Pulmonary Gas-Exchange, Alexander M. Matheson

Electronic Thesis and Dissertation Repository

Gas-exchange is the primary function of the lungs and involves removing carbon dioxide from the body and exchanging it within the alveoli for inhaled oxygen. Several different pulmonary, cardiac and cardiovascular abnormalities have negative effects on pulmonary gas-exchange. Unfortunately, clinical tests do not always pinpoint the problem; sensitive and specific measurements are needed to probe the individual components participating in gas-exchange for a better understanding of pathophysiology, disease progression and response to therapy.

In vivo Xenon-129 gas-exchange magnetic resonance imaging (¹²⁹Xe gas-exchange MRI) has the potential to overcome these challenges. When participants inhale hyperpolarized ¹²⁹Xe gas, it …

Increased Top-Down Control Of Emotions During Symptom Provocation Working Memory Tasks Following A Rct Of Alpha-Down Neurofeedback In Ptsd., Saurabh Bhaskar Shaw, Andrew A Nicholson, Tomas Ros, Sherain Harricharan, Braeden Terpou, Maria Densmore, Jean Theberge, Paul Frewen, Ruth A Lanius

Department of Medicine Publications

BACKGROUND: Posttraumatic stress disorder (PTSD) has been found to be associated with emotion under-modulation from the prefrontal cortex and a breakdown of the top-down control of cognition and emotion. Novel adjunct therapies such as neurofeedback (NFB) have been shown to normalize aberrant neural circuits that underlie PTSD psychopathology at rest. However, little evidence exists for NFB-linked neural improvements under emotionally relevant cognitive load. The current study sought to address this gap by examining the effects of alpha-down NFB in the context of an emotional n-back task.

METHODS: We conducted a 20-week double-blind randomized, sham-controlled trial of alpha-down NFB and collected …

How The Body Remembers: Examining The Default Mode And Sensorimotor Networks During Moral Injury Autobiographical Memory Retrieval In Ptsd., Breanne E Kearney, Braeden A Terpou, Maria Densmore, Saurabh B Shaw, Jean Theberge, Rakesh Jetly, Margaret C Mckinnon, Ruth A Lanius

Department of Medicine Publications

Neural representations of sensory percepts and motor responses constitute key elements of autobiographical memory. However, these representations may remain as unintegrated sensory and motor fragments in traumatic memory, thus contributing toward re-experiencing and reliving symptoms in trauma-related conditions such as post-traumatic stress disorder (PTSD). Here, we investigated the sensorimotor network (SMN) and posterior default mode network (pDMN) using a group independent component analysis (ICA) by examining their functional connectivity during a script-driven memory retrieval paradigm of (potentially) morally injurious events in individuals with PTSD and healthy controls. Moral injury (MI), where an individual acts or fails to act in a …

Planning System For The Optimization Of Electric Field Delivery Using Implanted Electrodes For Brain Tumor Control, Erin Iredale, Brynn Voigt, Adam Rankin, Kyungho W Kim, Jeff Z Chen, Susanne Schmid, Matthew O Hebb, Terry M Peters, Eugene Wong

Anatomy and Cell Biology Publications

BACKGROUND: The use of non-ionizing electric fields from low-intensity voltage sources (< 10 V) to control malignant tumor growth is showing increasing potential as a cancer treatment modality. A method of applying these low-intensity electric fields using multiple implanted electrodes within or adjacent to tumor volumes has been termed as intratumoral modulation therapy (IMT).

PURPOSE: This study explores advancements in the previously established IMT optimization algorithm, and the development of a custom treatment planning system for patient-specific IMT. The practicality of the treatment planning system is demonstrated by implementing the full optimization pipeline on a brain phantom with robotic electrode implantation, postoperative imaging, and treatment stimulation.

METHODS: The integrated planning pipeline in 3D Slicer begins with importing and segmenting patient magnetic resonance images (MRI) or computed tomography (CT) images. The segmentation process is manual, followed by a semi-automatic smoothing step that allows …

Magnetic Resonance Systems Development For Point-Of-Care Mri Platforms, Eric J. Lessard

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging utilizes electromagnets to produce anatomical images in both clinical and research settings. In the race towards increasing performance head-optimized scanners have begun playing a significant role in providing high quality imaging of the head. However, they are implemented using smaller geometries and as such fail to allow entrance of the patient past their shoulders. This is overcome by designing asymmetric gradient coils which have their imaging region located towards one end of the gradient coil, as opposed to the geometric center, allowing brain imaging. There exists interest in compact configurations which allow imaging further into the cervical …

In Vivo Magnetic Resonance Spectroscopy Of Hyperpolarized [1-, Lauren M Smith, Conrad B Pitts, Lanette J Friesen-Waldner, Neetin H Prabhu, Katherine E Mathers, Kevin J Sinclair, Trevor P Wade, Timothy Regnault, Charles A Mckenzie

Paediatrics Publications

BACKGROUND: Alterations in glycolysis are central to the increasing incidence of non-alcoholic fatty liver disease (NAFLD), highlighting a need for in vivo, non-invasive technologies to understand the development of hepatic metabolic aberrations.

PURPOSE: To use hyperpolarized magnetic resonance spectroscopy (MRS) and proton density fat fraction (PDFF) magnetic resonance imaging (MRI) techniques to investigate the effects of a chronic, life-long exposure to the Western diet (WD) in an animal model resulting in NAFLD; to investigate the hypothesis that exposure to the WD will result in NAFLD in association with altered pyruvate metabolism.

STUDY TYPE: Prospective.

ANIMAL MODEL: Twenty-eight male guinea pigs …

Measuring Inflammation In The Entire Myocardium In A Canine Model Of Myocardial Infarction With Hybrid Pet/Mri, Benjamin Wilk

Electronic Thesis and Dissertation Repository

Background: After myocardial infarction (MI), fibrosis and an ongoing dysregulated inflammatory response are associated with adverse cardiac remodeling. Fluorodeoxyglucose (FDG) positron emission tomography (PET) is sensitive to inflammation provided suppression protocols are implemented to restrict the uptake of glucose in myocytes. Magnetic resonance imaging can be used to determine extracellular volume, a surrogate measure of fibrosis. In some cases, patients present with markedly reduced flow in the setting of a large infarct, i.e. microvascular obstruction, restricting the delivery of FDG and contrast agents. To overcome this problem, a constant infusion was explored as an alternative to the clinical standard bolus …

Water-Fat Magnetic Resonance Imaging Of Adipose Tissue Compartments In The Normal Third Trimester Fetus, Stephanie A Giza, Tianna L Koreman, Simran Sethi, Michael R Miller, Debbie A Penava, Genevieve D Eastabrook, Charles A Mckenzie, Barbra De Vrijer

Obstetrics & Gynaecology Publications

BACKGROUND: Assessment of fetal adipose tissue gives information about the future metabolic health of an individual, with evidence that the development of this tissue has regional heterogeneity.

OBJECTIVE: To assess differences in the proton density fat fraction (PDFF) between fetal adipose tissue compartments in the third trimester using water-fat magnetic resonance imaging (MRI).

MATERIALS AND METHODS: Water-fat MRI was performed in a 1.5-T scanner. Fetal adipose tissue was segmented into cheeks, thorax, abdomen, upper arms, forearms, thighs and lower legs. PDFF and R2* values were measured in each compartment.

RESULTS: Twenty-eight women with singleton pregnancies were imaged between 28 and …

Ischemic Stroke Thrombus Characterization Through Quantitative Magnetic Resonance Imaging, Spencer D. Christiansen

Electronic Thesis and Dissertation Repository

Stroke is a pervasive, devastating disease and remains one of the most challenging conditions to treat. In particular, risk of recurrence is dramatically heightened after a primary stroke and requires urgent preventative therapy to effectively mitigate. However, the appropriate preventative therapy depends on the underlying source of the stroke, known as etiology, which is challenging to determine promptly. Current diagnostic tests for determining etiology underwhelm in both sensitivity and specificity, and in as much as 35% of cases etiology is never determined. In ischemic stroke, the composition of the occluding thrombus, specifically its red blood cell (RBC) content, has been …

The Application Of In Utero Magnetic Resonance Imaging In The Study Of The Metabolic And Cardiovascular Consequences Of The Developmental Origins Of Health And Disease, Stephanie A. Giza, Simran Sethi, Lauren M. Smith, Mary Ellen E.T. Empey, Lindsay E. Morris, Charles A. Mckenzie

Paediatrics Publications

Observing fetal development in utero is vital to further the understanding of later-life diseases. Magnetic resonance imaging (MRI) offers a tool for obtaining a wealth of information about fetal growth, development, and programming not previously available using other methods. This review provides an overview of MRI techniques used to investigate the metabolic and cardiovascular consequences of the developmental origins of health and disease (DOHaD) hypothesis. These methods add to the understanding of the developing fetus by examining fetal growth and organ development, adipose tissue and body composition, fetal oximetry, placental microstructure, diffusion, perfusion, flow, and metabolism. MRI assessment of fetal …

Comparing Neuromuscular System Function In Healthy And Mobility-Impaired Older Females, Neal B. Mckinnon

Electronic Thesis and Dissertation Repository

Objectives: The objective of this thesis was to evaluate and compare neuromuscular system function in a group of young, healthy old and mobility-impaired older females (gait speed less than 1m/s) in an attempt to identify which neuromuscular factors contribute most to the loss of mobility and functional performance with age.

Methods: The ankle dorsiflexor and knee extensor muscles were used as a model in these studies. First, in Chapter 2 quantitative electromyography (EMG) was used to evaluate motor unit (MU) numbers, properties and the fidelity of the neuromuscular junction. Next, Chapter 3 conducted magnetic resonance imaging (MRI) to examine contractile …

Computational Unfolding Of The Human Hippocampus, Jordan M. K. Dekraker

Electronic Thesis and Dissertation Repository

The hippocampal subfields are defined by their unique cytoarchitectures, which many recent studies have tried to map to human in-vivo MRI because of their promise to further our understanding of hippocampal function, or its dysfunction in disease. However, recent anatomical literature has highlighted broad inter-individual variability in hippocampal morphology and subfield locations, much of which can be attributed to different folding configurations within hippocampal (or archicortical) tissue. Inspired in part by analogous surface-based neocortical analysis methods, the current thesis aimed to develop a standardized coordinate framework, or surface-based method, that respects the topology of all hippocampal folding configurations. I developed …

Atrx Deletion In Neurons Leads To Sexually Dimorphic Dysregulation Of Mir-137 And Spatial Learning And Memory Deficits., Renee J. Tamming, Vanessa Dumeaux, Yan Jiang, Sarfraz Shafiq, Luana Langlois, Jacob Ellegood, Lily R. Qiu, Jason P. Lerch, Nathalie G. Bérubé

Paediatrics Publications

ATRX gene mutations have been identified in syndromic and non-syndromic intellectual disabilities in humans. ATRX is known to maintain genomic stability in neuroprogenitor cells, but its function in differentiated neurons and memory processes remains largely unresolved. Here, we show that the deletion of neuronal Atrx in mice leads to distinct hippocampal structural defects, fewer presynaptic vesicles, and an enlarged postsynaptic area at CA1 apical dendrite-axon junctions. We identify male-specific impairments in long-term contextual memory and in synaptic gene expression, linked to altered miR-137 levels. We show that ATRX directly binds to the miR-137 locus and that the enrichment of the …

Neural Activity During Self-Referential Processing In Children At Risk For Depression., Pan Liu, Matthew R J Vandermeer, Marc F Joanisse, Deanna M Barch, David J A Dozois, Elizabeth P Hayden

Psychology Publications

BACKGROUND: According to cognitive theories of depression, more negative and less positive self-schemas are thought to play a causal role in the disorder. Existing evidence speaks to the neural substrates of self-referential processes in both healthy and depressed individuals, but little is known about how the brain relates to self-referential processing in the context of depression risk in children. We therefore studied the neural substrates of self-referential processing in never-depressed preadolescent children at high and low risk for depression based on maternal depression history.

METHODS: A total of 87 never-depressed 10-12-year-old children (29 with maternal depression) completed a self-referential encoding …

Osteochondritis Dissecans In Pediatric Patients With Juvenile Idiopathic Arthritis., Bradley C Jackson, Debra L Bartley, Roberta A Berard

Paediatrics Publications

No abstract provided.

Pulmonary Imaging Of Chronic Obstructive Pulmonary Disease Using Multi-Parametric Response Maps, Jonathan Macneil

Electronic Thesis and Dissertation Repository

Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airflow obstruction caused by airway remodelling and parenchymal destruction. Clinically, observation of COPD is performed using spirometry, but this technique only provides a global measure of lung health. To supplement these clinical measurements, thoracic computed tomography (CT) and hyperpolarized gas magnetic resonance imaging (MRI) have been used to measure regional structure and function abnormalities. Although CT and MRI have been used to research COPD, combination of both modalities into an interrelated image has never been performed. Therefore, we developed an image processing pipeline to combine MRI-CT information into a multi-parametric response …

The Hijacked Self: Disrupted Functional Connectivity Between The Periaqueductal Gray And The Default Mode Network In Posttraumatic Stress Disorder Using Dynamic Causal Modeling., Braeden A Terpou, Maria Densmore, Jean Theberge, Paul Frewen, Margaret C Mckinnon, Andrew A Nicholson, Ruth A Lanius

Department of Medicine Publications

Self-related processes define assorted self-relevant or social-cognitive functions that allow us to gather insight and to draw inferences related to our own mental conditions. Self-related processes are mediated by the default mode network (DMN), which, critically, shows altered functionality in individuals with posttraumatic stress disorder (PTSD). In PTSD, the midbrain periaqueductal gray (PAG) demonstrates stronger functional connectivity with the DMN [i.e., precuneus (PCN), medial prefrontal cortex (mPFC)] as compared to healthy individuals during subliminal, trauma-related stimulus processing. Here, we analyzed the directed functional connectivity between the PAG and the PCN, as well as between the PAG and the mPFC to …

A Randomized, Controlled Trial Of Alpha-Rhythm Eeg Neurofeedback In Posttraumatic Stress Disorder: A Preliminary Investigation Showing Evidence Of Decreased Ptsd Symptoms And Restored Default Mode And Salience Network Connectivity Using Fmri., Andrew A Nicholson, Tomas Ros, Maria Densmore, Paul A Frewen, Richard W J Neufeld, Jean Theberge, Rakesh Jetly, Ruth A Lanius

Department of Medicine Publications

OBJECTIVE: The default-mode network (DMN) and salience network (SN) have been shown to display altered connectivity in posttraumatic stress disorder (PTSD). Restoring aberrant connectivity within these networks with electroencephalogram neurofeedback (EEG-NFB) has been shown previously to be associated with acute decreases in symptoms. Here, we conducted a double-blind, sham-controlled randomized trial of alpha-rhythm EEG-NFB in participants with PTSD (n = 36) over 20-weeks. Our aim was to provide mechanistic evidence underlying clinical improvements by examining changes in network connectivity via fMRI.

METHODS: We randomly assigned participants with a primary diagnosis of PTSD to either the experimental group (n = 18) …

Chronic Obstructive Pulmonary Disease: Thoracic Ct Texture Analysis And Machine Learning To Predict Pulmonary Ventilation, Andrew Westcott, Dante P I Capaldi, David G Mccormack, Aaron D Ward, Aaron Fenster, Grace Parraga

Medical Biophysics Publications

Background Fixed airflow limitation and ventilation heterogeneity are common in chronic obstructive pulmonary disease (COPD). Conventional noncontrast CT provides airway and parenchymal measurements but cannot be used to directly determine lung function. Purpose To develop, train, and test a CT texture analysis and machine-learning algorithm to predict lung ventilation heterogeneity in participants with COPD. Materials and Methods In this prospective study (

An Accurate Registration Of The Bigbrain Dataset With The Mni Pd25 And Icbm152 Atlases., Yiming Xiao, Jonathan C Lau, Taylor Anderson, Jordan Dekraker, D Louis Collins, Terry Peters, Ali R Khan

Brain and Mind Institute Researchers' Publications

Brain atlases that encompass detailed anatomical or physiological features are instrumental in the research and surgical planning of various neurological conditions. Magnetic resonance imaging (MRI) has played important roles in neuro-image analysis while histological data remain crucial as a gold standard to guide and validate such analyses. With cellular-scale resolution, the BigBrain atlas offers 3D histology of a complete human brain, and is highly valuable to the research and clinical community. To bridge the insights at macro- and micro-levels, accurate mapping of BigBrain and established MRI brain atlases is necessary, but the existing registration is unsatisfactory. The described dataset includes …

A Framework For Evaluating Correspondence Between Brain Images Using Anatomical Fiducials., Jonathan C Lau, Andrew G Parrent, John Demarco, Geetika Gupta, Jason Kai, Olivia W Stanley, Tristan Kuehn, Patrick J Park, Kayla Ferko, Ali R Khan, Terry M Peters

Brain and Mind Institute Researchers' Publications

Accurate spatial correspondence between template and subject images is a crucial step in neuroimaging studies and clinical applications like stereotactic neurosurgery. In the absence of a robust quantitative approach, we sought to propose and validate a set of point landmarks, anatomical fiducials (AFIDs), that could be quickly, accurately, and reliably placed on magnetic resonance images of the human brain. Using several publicly available brain templates and individual participant datasets, novice users could be trained to place a set of 32 AFIDs with millimetric accuracy. Furthermore, the utility of the AFIDs protocol is demonstrated for evaluating subject-to-template and template-to-template registration. Specifically, …

The Effect Of Spatial Averaging On Db/Dt Exposure Values For Implanted Medical Devices, Christopher Ap Brown

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) is a medical imaging modality that has seen continuous growth in the decades since its introduction. In conjunction with this increase in the use of MRI, there has also been a growth in the number of patients having implanted medical devices, such as pacemakers. These devices can have undesirable interactions with the MR system. The safety of these interactions must be guaranteed while ensuring that safety limits are not so conservative that they would preclude too many patients from benefiting from MRI. One factor that could make limits less restrictive is spatial averaging of the fields …

Development Of A Computational Method For Assessing Static Field Induced Torque On Medical Implants, Xiao Fan Ding

Electronic Thesis and Dissertation Repository

The objective of this thesis is the development of a computational method for finding the torque induced on an object when placed in the static magnetic field of an MR scanner. As a preliminary step, the classic EM problems of a sphere and infinitely long cylinder of linear material was modeled in commercially available simulation software. Upon verification of the parameters implemented, the second step is the simulation of simple objects with realistic material properties, stainless-steel cylinders. Physical cylinders were machined to match those in the simulations and underwent the ASTM standard method for measuring induced torque. An adjacent study …

Hyperpolarized Helium 3 Mri In Mild-To-Moderate Asthma: Prediction Of Postbronchodilator Reversibility, Rachel L Eddy, Sarah Svenningsen, Christopher Licskai, David G Mccormack, Grace Parraga

Medical Biophysics Publications

Background: Longitudinal progression to irreversible airflow limitation occurs in approximately 10% of patients with asthma, but it is difficult to identify patients who are at risk for this transition.

Purpose: To investigate 6-year longitudinal changes in hyperpolarized helium 3 (3He) MRI ventilation defects in study participants with mild-to-moderate asthma and identify predictors of longitudinal changes in postbronchodilator forced expiratory volume in 1 second (FEV1) reversibility

Materials and Methods: Spirometry and hyperpolarized 3He MRI were evaluated in participants with mild-to-moderate asthma in two prospectively planned visits approximately 6 years apart. Participants underwent methacholine challenge at baseline (January 2010 to April 2011) …

Brain Activity Associated With Dual-Task Performance Of Ankle Motor Control During Cognitive Challenge., Sue Peters, Janice J Eng, Teresa Liu-Ambrose, Michael R Borich, Elizabeth Dao, Ameen Amanian, Lara A Boyd

Physical Therapy Publications

INTRODUCTION: Skilled Ankle motor control is frequently required while performing secondary cognitively demanding tasks such as socializing and avoiding obstacles while walking, termed "Dual tasking." It is likely that Dual-task performance increases demand on the brain, as both motor and cognitive systems require neural resources. The purpose of this study was to use functional MRI to understand which brain regions are involved in resolving Dual-task interference created by requiring high levels of Ankle motor control during a cognitive task.

METHODS: Using functional MRI, brain activity was measured in sixteen young adults during performance of visually cued Ankle plantar flexion to …

Texture Analysis And Machine Learning To Predict Pulmonary Ventilation From Thoracic Computed Tomography, Andrew Westcott

Electronic Thesis and Dissertation Repository

Chronic obstructive pulmonary disease (COPD) leads to persistent airflow limitation, causing a large burden to patients and the health care system. Thoracic CT provides an opportunity to observe the structural pathophysiology of COPD, whereas hyperpolarized gas MRI provides images of the consequential ventilation heterogeneity. However, hyperpolarized gas MRI is currently limited to research centres, due to the high cost of gas and polarization equipment. Therefore, I developed a pipeline using texture analysis and machine learning methods to create predicted ventilation maps based on non-contrast enhanced, single-volume thoracic CT. In a COPD cohort, predicted ventilation maps were qualitatively and quantitatively related …