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, …

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 …

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 …

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 …

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

Paediatrics Publications

No abstract provided.

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) …

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, …

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 …

White Matter Biomarkers Associated With Motor Change In Individuals With Stroke: A Continuous Theta Burst Stimulation Study, K P Wadden, Sue Peters, M R Borich, J L Neva, K S Hayward, C S Mang, N J Snow, K E Brown, T S Woodward, S K Meehan, L A Boyd

Physical Therapy Publications

Continuous theta burst stimulation (cTBS) is a form of noninvasive repetitive brain stimulation that, when delivered over the contralesional hemisphere, can influence the excitability of the ipsilesional hemisphere in individuals with stroke. cTBS applied prior to skilled motor practice interventions may augment motor learning; however, there is a high degree of variability in individual response to this intervention. The main objective of the present study was to assess white matter biomarkers of response to cTBS paired with skilled motor practice in individuals with chronic stroke. We tested the effects of stimulation of the contralesional hemisphere at the site of the …

7t Magnetic Resonance Spectroscopy Of Non-Lesional Temporal Lobe Epilepsy, John Robert Adams

Electronic Thesis and Dissertation Repository

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy, and one that is generally amenable to surgical treatment when surgery is necessary. Unfortunately, roughly 25-30% of the patient population have no visible lesions on clinical MRI scans. Without anatomical abnormalities to help guide surgical resection, the success of surgical treatment decreases substantially. However, metabolic abnormalities may exist that could allow for accurate localization of epileptic tissue in this cohort. Magnetic resonance spectroscopy (MRS) is a technique that can detect and measure the concentration of metabolically important molecules within tissue, giving insight into the underlying cellular metabolism.

In …

Magnetic Resonance Imaging In The Diagnosis Of White Matter Signal Abnormalities., Ravi Datar, Asuri Narayan Prasad, Keng Yeow Tay, Charles Anthony Rupar, Pavlo Ohorodnyk, Michael Miller, Chitra Prasad

Paediatrics Publications

Background White matter abnormalities (WMAs) pose a diagnostic challenge when trying to establish etiologic diagnoses. During childhood and adult years, genetic disorders, metabolic disorders and acquired conditions are included in differential diagnoses. To assist clinicians and radiologists, a structured algorithm using cranial magnetic resonance imaging (MRI) has been recommended to aid in establishing working diagnoses that facilitate appropriate biochemical and genetic investigations. This retrospective pilot study investigated the validity and diagnostic utility of this algorithm when applied to white matter signal abnormalities (WMSAs) reported on imaging studies of patients seen in our clinics. Methods The MRI algorithm was applied to …

Oscillometry And Pulmonary Mri Measurements Of Ventilation Heterogeneity In Obstructive Lung Disease: Relationship To Quality Of Life And Disease Control, Heather M Young, Fumin Guo, Rachel L Eddy, Geoffrey Maksym, Grace Parraga

Medical Biophysics Publications

Ventilation heterogeneity is a hallmark finding in obstructive lung disease and may be evaluated using a variety of methods, including multiple-breath gas washout and pulmonary imaging. Such methods provide an opportunity to better understand the relationships between structural and functional abnormalities in the lungs, and their relationships with important clinical outcomes. We measured ventilation heterogeneity and respiratory impedance in 100 subjects [50 patients with asthma, 22 ex-smokers, and 28 patients with chronic obstructive pulmonary disease (COPD)] using oscillometry and hyperpolarized

Type-2 Diabetes Mellitus Reduces Cortical Thickness And Decreases Oxidative Metabolism In Sensorimotor Regions After Stroke., Jennifer K Ferris, Sue Peters, Katlyn E Brown, Katherine Tourigny, Lara A Boyd

Physical Therapy Publications

Individuals with type-2 diabetes mellitus experience poor motor outcomes after ischemic stroke. Recent research suggests that type-2 diabetes adversely impacts neuronal integrity and function, yet little work has considered how these neuronal changes affect sensorimotor outcomes after stroke. Here, we considered how type-2 diabetes impacted the structural and metabolic function of the sensorimotor cortex after stroke using volumetric magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). We hypothesized that the combination of chronic stroke and type-2 diabetes would negatively impact the integrity of sensorimotor cortex as compared to individuals with chronic stroke alone. Compared to stroke alone, individuals with …

Imaging Biomarkers Of Pulmonary Structure And Function, Dante Capaldi

Electronic Thesis and Dissertation Repository

Asthma and chronic obstructive pulmonary disease (COPD) are characterized by airflow limitations resulting from airway obstruction and/or tissue destruction. The diagnosis and monitoring of these pulmonary diseases is primarily performed using spirometry, specifically the forced expiratory volume in one second (FEV₁), which measures global airflow obstruction and provides no regional information of the different underlying disease pathologies. The limitations of spirometry and current therapies for lung disease patients have motivated the development of pulmonary imaging approaches, such as computed tomography (CT) and magnetic resonance imaging (MRI). Inhaled hyperpolarized noble gas MRI, specifically using helium-3 (³He) and …

Human Neuroimaging Reveals The Subcomponents Of Grasping, Reaching And Pointing Actions., Cristiana Cavina-Pratesi, Jason D Connolly, Simona Monaco, Teresa D Figley, A David Milner, Thomas Schenk, Jody C Culham

Brain and Mind Institute Researchers' Publications

Although the neural underpinnings of visually guided grasping and reaching have been well delineated within lateral and medial fronto-parietal networks (respectively), the contributions of subcomponents of visuomotor actions have not been explored in detail. Using careful subtraction logic, here we investigated which aspects of grasping, reaching, and pointing movements drive activation across key areas within visuomotor networks implicated in hand actions. For grasping tasks, we find activation differences based on the precision required (fine > coarse grip: anterior intraparietal sulcus, aIPS), the requirement to lift the object (grip + lift > grip: aIPS; dorsal premotor cortex, PMd; and supplementary motor area, SMA), …

Evaluating Small Airways Disease In Asthma And Copd Using The Forced Oscillation Technique And Magnetic Resonance Imaging, Heather M. Young

Electronic Thesis and Dissertation Repository

Obstructive lung disease, including asthma and chronic obstructive pulmonary disease (COPD), is characterized by heterogeneous ventilation. Unfortunately, the underlying structure-function relationships and the relationships between measurements of heterogeneity and patient quality-of-life in obstructive lung disease are not well understood. Hyperpolarized noble gas MRI is used to visualize and quantify ventilation distribution and the forced oscillation technique (FOT) applies a multi-frequency pressure oscillation at the mouth to measure respiratory impedance to airflow (including resistance and reactance). My objective was to use FOT, ventilation MRI and computational airway tree modeling to better understand ventilation heterogeneity in asthma and COPD. FOT-measured respiratory system …

Mri Ventilation Abnormalities Predict Quality-Of-Life And Lung Function Changes In Mild-To-Moderate Copd: Longitudinal Tincan Study, Miranda Kirby, Rachel L Eddy, Damien Pike, Sarah Svenningsen, Harvey O Coxson, Don D Sin, David G Mccormack, Grace Parraga

Medical Biophysics Publications

CT biomarkers of emphysema (15th percentile of the CT density histogram, HU15%) and airways disease (wall thickness of airways with 10 mm internal perimeter, Pi10) have shown promise for providing prognostic information.2 Although recent data3 showed that the change in CT emphysema may be used to estimate the efficacy of therapy in patients with α-1-antitrypsin-deficiency, thus far none of the currently developed CT biomarkers have been shown to reflect changes in outcomes that are important to patients with COPD. MRI with inhaled noble gases provide highly sensitive and unique microstructural and functional information in COPD.4 MRI biomarkers of COPD are …

Multi-Nuclear Magnetic Resonance Imaging Of Obstructive Lung Disease, Khadija Sheikh

Electronic Thesis and Dissertation Repository

Obstructive lung diseases such as chronic-obstructive-lung-disease (COPD), bronchiectasis, and asthma are characterized by airflow obstruction. They affect over six million Canadians costing the economy $12 billion/year. Despite decades of research, therapies that modify obstructive-lung-disease progression and control are lacking because patient diagnosis, monitoring, and response to therapy are currently made using airflow measurements that may conceal the independent contributions of underlying pathologies. One goal of obstructive-lung-disease research is to develop ways to identify patients with specific underlying pathological phenotypes to improve patient care and outcomes. Thoracic computed-tomography (CT) and magnetic-resonance-imaging (MRI) provide ways to regionally identify the underlying pathologies associated …

Resting-State Network-Specific Breakdown Of Functional Connectivity During Ketamine Alteration Of Consciousness In Volunteers., Vincent Bonhomme, Audrey Vanhaudenhuyse, Athena Demertzi, Marie-Aurélie Bruno, Oceane Jaquet, Mohamed Ali Bahri, Alain Plenevaux, Melanie Boly, Pierre Boveroux, Andrea Soddu, Jean François Brichant, Pierre Maquet, Steven Laureys

Brain and Mind Institute Researchers' Publications

BACKGROUND: Consciousness-altering anesthetic agents disturb connectivity between brain regions composing the resting-state consciousness networks (RSNs). The default mode network (DMn), executive control network, salience network (SALn), auditory network, sensorimotor network (SMn), and visual network sustain mentation. Ketamine modifies consciousness differently from other agents, producing psychedelic dreaming and no apparent interaction with the environment. The authors used functional magnetic resonance imaging to explore ketamine-induced changes in RSNs connectivity.

METHODS: Fourteen healthy volunteers received stepwise intravenous infusions of ketamine up to loss of responsiveness. Because of agitation, data from six subjects were excluded from analysis. RSNs connectivity was compared between absence of …

Usage Of Swi (Susceptibility Weighted Imaging) Acquired At 7t For Qualitative Evaluation Of Temporal Lobe Epilepsy Patients With Histopathological And Clinical Correlation: An Initial Pilot Study., Benjamin Y M Kwan, Fateme Salehi, Pavlo Ohorodnyk, Donald H Lee, Jorge G Burneo, Seyed M Mirsattari, David Steven, Robert Hammond, Terry M Peters, Ali R Khan

Brain and Mind Institute Researchers' Publications

OBJECTIVES: Ultra high field MRI at 7T is able to provide much improved spatial and contrast resolution which may aid in the diagnosis of hippocampal abnormalities. This paper presents a preliminary experience on qualitative evaluation of 7T MRI in temporal lobe epilepsy patients with a focus on comparison to histopathology.

METHODS: 7T ultra high field MRI data, using T1-weighted, T2*-weighted and susceptibility-weighted images (SWI), were acquired for 13 patients with drug resistant temporal lobe epilepsy (TLE) during evaluation for potential epilepsy surgery. Qualitative evaluation of the imaging data for scan quality and presence of hippocampal and temporal lobe abnormalities were …

Hyperpolarized 3he Magnetic Resonance Imaging Phenotypes Of Chronic Obstructive Pulmonary Disease, Damien Pike

Electronic Thesis and Dissertation Repository

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in the world. Identifying clinically relevant COPD phenotypes has the potential to reduce the global burden of COPD by helping to alleviate symptoms, slow disease progression and prevent exacerbation by stratifying patient cohorts and forming targeted treatment plans. In this regard, quantitative pulmonary imaging with hyperpolarized 3He magnetic resonance imaging (MRI) and thoracic computed tomography (CT) have emerged as ways to identify and measure biomarkers of lung structure and function. 3He MRI may be used as a tool to probe both functional and structural properties of the lung …

In Vivo Mri Signatures Of Hippocampal Subfield Pathology In Intractable Epilepsy., Maged Goubran, Boris C Bernhardt, Diego Cantor-Rivera, Jonathan C Lau, Charlotte Blinston, Robert R Hammond, Sandrine De Ribaupierre, Jorge G Burneo, Seyed M Mirsattari, David A Steven, Andrew G Parrent, Andrea Bernasconi, Neda Bernasconi, Terry M Peters, Ali R Khan

Brain and Mind Institute Researchers' Publications

OBJECTIVES: Our aim is to assess the subfield-specific histopathological correlates of hippocampal volume and intensity changes (T1, T2) as well as diff!usion MRI markers in TLE, and investigate the efficacy of quantitative MRI measures in predicting histopathology in vivo.

EXPERIMENTAL DESIGN: We correlated in vivo volumetry, T2 signal, quantitative T1 mapping, as well as diffusion MRI parameters with histological features of hippocampal sclerosis in a subfield-specific manner. We made use of on an advanced co-registration pipeline that provided a seamless integration of preoperative 3 T MRI with postoperative histopathological data, on which metrics of cell loss and gliosis were quantitatively …

Pulmonary Ct And Mri Phenotypes That Help Explain Chronic Pulmonary Obstruction Disease Pathophysiology And Outcomes, Eric A Hoffman, David A Lynch, R Graham Barr, Edwin J R Van Beek, Grace Parraga

Medical Biophysics Publications

Pulmonary x-ray computed tomographic (CT) and magnetic resonance imaging (MRI) research and development has been motivated, in part, by the quest to subphenotype common chronic lung diseases such as chronic obstructive pulmonary disease (COPD). For thoracic CT and MRI, the main COPD research tools, disease biomarkers are being validated that go beyond anatomy and structure to include pulmonary functional measurements such as regional ventilation, perfusion, and inflammation. In addition, there has also been a drive to improve spatial and contrast resolution while at the same time reducing or eliminating radiation exposure. Therefore, this review focuses on our evolving understanding of …

Design And Evaluation Of An Mri-Compatible Linear Motion Stage., Mohammad Ali Tavallaei, Patricia M Johnson, Junmin Liu, Maria Drangova

Medical Biophysics Publications

PURPOSE: To develop and evaluate a tool for accurate, reproducible, and programmable motion control of imaging phantoms for use in motion sensitive magnetic resonance imaging (MRI) appli cations.

METHODS: In this paper, the authors introduce a compact linear motion stage that is made of nonmagnetic material and is actuated with an ultrasonic motor. The stage can be positioned at arbitrary positions and orientations inside the scanner bore to move, push, or pull arbitrary phantoms. Using optical trackers, measuring microscopes, and navigators, the accuracy of the stage in motion control was evaluated. Also, the effect of the stage on image signal-to-noise …

Pulmonary Imaging To Better Understand Asthma, Sarah Svenningsen

Electronic Thesis and Dissertation Repository

Asthma is characterized using the spirometry measurement of the forced expiratory volume in one second (FEV₁). Simple and inexpensive, FEV₁ provides a global estimate of lung function but this metric cannot regionally identify airways responsible for airflow limitation, asthma symptoms or control. Work that brought about an understanding that airway abnormalities are heterogeneously distributed within the lung in asthma patients has motivated the development of pulmonary imaging approaches, such as hyperpolarized helium-3 (³He) and xenon-129 (¹²⁹Xe) magnetic resonance imaging (MRI). These methods provide a way to visualize and quantify lung regions accessed by …

Dual Optimization Method Of Radiofrequency And Quasistatic Field Simulations For Reduction Of Eddy Currents Generated On 7t Radiofrequency Coil Shielding., Yujuan Zhao, Tiejun Zhao, Shailesh B Raval, Narayanan Krishnamurthy, Hai Zheng, Chad T Harris, William B Handler, Blaine A Chronik, Tamer S Ibrahim

Brain and Mind Institute Researchers' Publications

PURPOSE: To optimize the design of radiofrequency (RF) shielding of transmit coils at 7T and reduce eddy currents generated on the RF shielding when imaging with rapid gradient waveforms.

METHODS: One set of a four-element, 2 × 2 Tic-Tac-Toe head coil structure was selected and constructed to study eddy currents on the RF coil shielding. The generated eddy currents were quantitatively studied in the time and frequency domains. The RF characteristics were studied using the finite difference time domain method. Five different kinds of RF shielding were tested on a 7T MRI scanner with phantoms and in vivo human subjects. …