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MA, DANMagnetic Resonance Fingerprinting
Doctor of Philosophy, Case Western Reserve University, 2015, Biomedical Engineering
Magnetic Resonance (MR) is an exceptionally powerful and versatile measurement technique. The basic structure of an MR experiment has remained nearly constant for almost 50 years. Here we introduce a novel paradigm, Magnetic Resonance Fingerprinting (MRF) that permits the non-invasive quantification of multiple important properties of a material or tissue simultaneously through a new approach to data acquisition and post-processing. MRF provides a new mechanism to quantitatively detect and analyze complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to specifically identify the presence of a target material or tissue, which will increase the sensitivity, specificity, and speed of an MR study, and potentially lead to new diagnostic testing methodologies. Because of its basis in pattern recognition, MRF inherently suppresses measurement errors and thus can improve accuracy and efficiency compared to previous approaches. By taking the advantage of the extra degrees of freedom of the MRF concept, the MRF-Music sequence is presented as a special form of the MRF to improve the patients’ comfort level during the MR scans while still maintaining a high image quality and scan efficiency.

Committee:

Mark Griswold (Advisor); Nicole Seiberlich (Committee Chair); Vikas Gulani (Committee Member); David Wilson (Committee Member); Jeffrey Duerk (Committee Member); Daniela Calvetti (Committee Member)

Subjects:

Biomedical Engineering

Keywords:

Magnetic Resonance Fingerprinting;T1 quantification;T2 quantification;Magnetic Resonance Imaging;Quantitative Magnetic Resonance Imaging

LaFountain, Richard AValidation of VO2max Assessment and Magnetic Resonance Cardiac Function Measurements Utilizing an MRI Compatible Treadmill
Master of Science, The Ohio State University, 2014, EDU Physical Activity and Educational Services
Abstract Maximum oxygen consumption (VO2max) is considered the gold standard for assessment of cardiorespiratory fitness. Likewise, MRI is considered the gold standard for quantification of cardiac function; however, the MRI-compatible equipment required to combine these two measures has not been available to date. We utilized a specially designed MRI-compatible treadmill, and modified oxygen uptake equipment to eliminate the ferromagnetic components of the mask and headgear to perform a standard VO2max treadmill test immediately adjacent to a clinical MRI system. We sought to determine if values for a VO2max test performed in an MRI room utilizing MRI-compatible equipment were valid and accurate when compared to those obtained in an exercise lab with typical equipment set up. Ten recreationally trained subjects completed two VO2max tests to volitional fatigue in two different settings; an exercise lab and an MRI room. Oxygen and carbon dioxide were measured continuously using a computerized system. Secondary criteria were assessed to confirm maximal exercise. Resting and peak exercise images of the heart were taken before and after maximal exercise to measure global cardiac function parameters including end systolic volume (ESV), end diastolic volume (EDV), cardiac output (CO) and left ventricular ejection fraction (LVEF). VO2max values were different (P=0.033) between testing locations (47.6±8.11 vs 50.0±10.7). All subjects met or exceeded a RER =1.10 and RPE =17 at peak exercise. iii (35.6 s. ± 3.8 s.) elapsed between the end of exercise and start of imaging. At rest vs immediately following peak stress, CO was (5.1 ± 1.0 vs 16.4 ± 5.6) and LVEF was (65.2 ± 3.3 vs 78.4 ± 4.8). Simultaneous VO2max testing was completed in 7 recreationally trained healthy individuals for comparison of the inter-unit variability in two ParvoMedics TrueOne 2400 systems. Despite the equipment modifications required to measure VO2max in the MRI environment, VO2 measurements correspond to those obtained in the exercise lab. The differences in both separate and simultaneous testing produced <4-6% error, within acceptable criteria according to national certification bodies, manufacturers specifications, and previously published studies. MRI-VO2max combined testing offers potential for advanced investigation of exercise physiology and cardiopulmonary disease.

Committee:

Steven Devor (Advisor); Orlando Simonetti (Advisor)

Subjects:

Kinesiology

Keywords:

VO2max; Cardiac Magnetic Resonance; CMR; Exercise; Treadmill; Magnetic Resonance Imaging; MRI

Sheth, Vipul RavindraA CEST MRI METHOD TO MEASURE pH
Doctor of Philosophy, Case Western Reserve University, 2011, Biomedical Engineering
Tumor pH is an important biomarker in cancer. In the following chapters an approach to measure pH by Chemical Exchange Saturation Transfer (CEST) MRI is described. Chapter 1 presents and introduction to molecular imaging, the importance of tumor pH and existing methods of pH measurement by various imaging modalities. Chapter 2 describes the characterization of a PARACEST MRI contrast agent, Yb-DO3A-oAA, for pH measurement. The pH measurement is independent of concentration and T1sat relaxation times, and covers a wider pH measurement range than alternative methods. A new method for fitting PARACEST spectra is shown. Chapter 3 demonstrates the self calibrating nature of CEST MRI with the contrast agent, Yb-DO3A-oAA-TML-ester, to detect esterase enzyme activity in solution and in cell culture media by generating an enzyme-responsive CEST effect that was compared with a control CEST effect from the same agent. In Chapter 4, a new MRI method was developed to simplify MRI acquisition of CEST spectra. Arrayed CEST-FISP and the parameters of this method were optimized for use with PARACEST agents. The arrayed CEST-FISP pulse program simplifies acquisition setup and subsequent analysis, and has strong potential to increase CEST experimental throughput that will facilitate future discoveries. Chapter 5 translates Yb-DO3A-oAA from in vitro to in vivo use to measure pH in a MDA-MB-231 tumor model and mouse muscle. The pharmacodynamics of Yb-DO3A-oAA are investigated and the fitting algorithm described in Chapter 2 is extended to in vivo tissues.

Committee:

Zheng-Rong Lu, PhD (Committee Chair); Christopher Flask, PhD (Committee Member); Vikas Gulani, MD. PhD (Committee Member); Roger Marchant, PhD (Committee Member); Mark Pagel, PhD (Advisor)

Subjects:

Biomedical Engineering

Keywords:

MRI; CEST; PARACEST; Paramagnetic; Saturation; pH; Magnetic Resonance; Chemical Exchange Saturation Transfer; Magnetic Resonance Imaging; Lanthanide

Burgess, Richard ElyMagnetic resonance imaging at ultra high field: implications for human neuroimaging
Doctor of Philosophy, The Ohio State University, 2004, Biomedical Engineering
Even before the development of magnetic resonance imaging, scientists and engineers repeatedly predicted that, despite the theoretical potential of high field, physical and engineering challenges would prevent the practical realization of gains in signal to noise. Many of the arguments used to disparage high field MRI can be divided into issues of uniform excitation, image distortion, and patient safety. In the former category lies challenges such as RF penetration limitations, dielectric resonances, coil self-resonance, coil-sample interactions, and RF power requirements, which may prevent uniform B1 can best be studied with numerical modeling techniques. Within the second category are effects such as chemical shift artifact, susceptibility distortions, and contrast convergence that can be well studied through analytic techniques and methodical manipulation of imaging parameters. In the category of safety belong RF power deposition and magnetohydrodynamic effects. In this thesis, issues of static field safety will be exhaustively explored and investigation of image contrast and quality will be undertaken to assess the potential of the 8 Tesla system for human neuroimaging. This thesis will specifically examine the theoretical risk of cardiac arrhythmia from induced currents and demonstrate the negligible cardiac, cognitive, and physiological bioeffects through animal and human studies. The extent of signal to noise ratio enhancement possible at 8 Tesla will be assessed and harnessed to obtain high resolution whole brain images. In the end, experimental results and analysis show that, despite the presence of artifact, high resolution images of the human brain with unique contrast can be safely obtained at 8 Tesla.

Committee:

Pierre-Marie Robitaille (Advisor)

Keywords:

magnetic resonance; magnetic resonance imaging; MRI; high field; 8 tesla; high resolution

Storrs, Judd M.Automatic Real-time Targeting of Single-Voxel Magnetic Resonance Spectroscopy
PhD, University of Cincinnati, 2010, Engineering and Applied Science: Biomedical Engineering

Magnetic resonance spectroscopy (MRS) is a non-invasive and non-destructive in vivo technique available on magnetic resonance imaging (MRI) scanners that is used to measure biochemical profiles from localized regions, or volumes-of-interest (VOIs), inside the body. A confounding factor for interpretation and analysis of MRS is spatial inconsistency in selection of VOIs for data collection, which may obscure biochemical alterations and reduce the statistical power of a study. Because VOI selection is performed manually by the MRI operator, consistency both between sessions and among subjects requires careful protocol design and experienced staff. Inter-subject anatomic variation, imprecise experimental protocols, and inter-operator variation contribute to VOI positioning error.

In this work, automatic targeting of VOIs using a standard anatomic atlas was hypothesized to improve spatial consistency for VOIs, both among subjects and between sessions. Subject anatomy is aligned to a template during acquisition of routine high-resolution 3D anatomic imaging. Alignment is computed parallel to acquisition and completes prior to the end of the scan allowing immediate use of the template coordinate system for the next scan. Once aligned, preselected VOIs are transferred from the template for acquisition. Two real-time alignment techniques are compared. The first performs affine alignment of the subject to the ICBM452 template, and the second rigidly aligns subject anatomy between baseline and followup sessions.

The technique was developed using simulations based on archived data from 79 subjects randomly segregated into training (40 subjects for development) and testing groups (39 subjects for evaluation). The accuracy of real-time spatial normalization was evaluated as disagreement with SPM5-derived nonlinear normalization. Median disagreement within the brain was 1.9 mm (largest: 9.1 mm). For comparison, optimal affine alignment was computed directly from nonlinear SPM5 results and had a median disagreement of 1.7 mm (largest: 7.7 mm). Median inter-session (test-retest) disagreement was 0.4 mm (largest: 1.9 mm) for the ICBM452-based technique and 0.2 mm (largest: 0.7 mm) for the rigid-body technique. Comparable results on training and testing groups indicate good generalization of both techniques beyond the training group.

Automatic and manual prescription of MRS was compared for VOIs in the anterior cingulate gyrus (ACG) and left and right inferior frontal gyri (L-IFG and R-IFG). Automatic ICBM452-based selection of nonoblique VOIs improved inter-subject overlap by +19.6%, +29.6%, and +22.4% (ACG, L-IFG, and R-IFG), and inter-session overlap by +16.2%, +15.7%, and +11.3% compared to manual VOI selections. Automatic ICBM452-based prescription of oblique VOIs provided further improvements for inter-subject overlap (+1.0%, +1.4%, +1.1%) and inter-session overlap (+3.0%, +3.2%, +2.7%). Rigid-body coregistration further improved inter-session overlap compared to ICBM452-based normalization both for nonoblique (+3.0%, +3.2%, +2.7%) and oblique (+0.6%, +0.3%, +0.6%) VOIs. Quantitative comparisons of VOI tissue content demonstrated improved anatomic consistency for automatic prescriptions compared to manually selected VOIs.

The availability of rapid, atlas-consistent inter-subject alignment is expected to simplify experimental protocols while simultaneously improving study-wide consistency. These improvements are expected to increase statistical power for group comparisons, facilitate atlas-based research (including combined fMRI and MRS studies), and support the development of biomarkers.

Committee:

Jing-Huei Lee, PhD (Committee Chair); Wen-Jang Chu, PhD (Committee Member); James Eliassen, PhD (Committee Member); William Ball, MD (Committee Member)

Subjects:

Biomedical Research

Keywords:

automatic prescription;brain mapping;magnetic resonance imaging (MRI);magnetic resonance spectroscopy (MRS);reproducibility;image registration

Chang, HenryMagnetic Resonance Imaging and Spectroscopy in the Evaluation and Management of Acute Coronary Syndrome
Doctor of Philosophy, The Ohio State University, 2015, Biomedical Engineering
An acute coronary syndrome (ACS) is a life-threatening event in the heart which affects over one million Americans each year. Although not currently part of the standard of care for ACS, magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques may be able to improve outcomes in patients with ACS. The majority of ACS cases are classified, using electrocardiogram (ECG), as non-ST segment acute coronary syndrome (NSTE-ACS). Diagnosis, risk assessment, and selection of management strategy can be difficult in this syndrome. A novel large animal model was created for study of NSTE-ACS by combining a partial coronary artery stenosis with ventricular pacing. In this animal model, MRI images of the heart were acquired, as well as oxygen respiration rates in myocardial tissue, troponin levels, and histology samples. T2 MRI, a technique which identifies myocardial regions with altered chemistry, was found to be elevated in ischemic myocardium. These T2 changes corresponded to reduced myocardial tissue respiratory function. Reperfusion reversed both T2 elevation and tissue respiratory depression, indicating that the early myocardial changes causing acute T2 elevation are reversible. This important property of T2 was supported by ultrastructural findings indicating myocardial viability and by the lack of late gadolinium enhancement (LGE) positivity or high troponins, which are tests to identify the presence of necrosed myocardium. An elevated T2 value thus may be a highly informative marker of acute reversible myocardial injury in NSTE-ACS and may reflect cellular changes (including respiratory function) which are not detectable by other tests or modalities yet have important implications on clinical decisions for patient management. Reversibly injured myocardium (identified by elevated T2) represents a target for reperfusion strategies that can prevent the progression to myocyte death and restore normal myocardial functionality. After an ACS, all patients are highly recommended to participate in a cardiac rehabilitation / secondary prevention (CR/SP) program, which has been shown to improve outcome metrics in patients such as mortality, quality of life, exercise capacity, and glucose control. However, some cellular properties like mitochondrial function and intramuscular fat, while important to patient health, are difficult to measure and so are not included as part of CR/SP evaluation of patients. Optimized techniques to non-invasively measure in vivo mitochondrial function, using 31P MRS, and intramuscular fat, using 1H MRS, were tested for reproducibility in volunteers. Once a suitable protocol was validated, measurements in ACS patients at the beginning of their CR/SP program were taken. This protocol was found to be reliably performed in a timely manner in any post-ACS patient who does not have MRI contraindications. Changes in mitochondrial function and intramuscular fat due to CR/SP interventions (such as modifications to exercise and diet habits) can be quantified using this protocol and used to evaluate the effectiveness of the CR/SP program. CR/SP supervisors thus may be able to tailor specific programs and activities to optimize the benefits to mitochondrial function and intramuscular fat and improve patient outcomes.

Committee:

Subha Raman, MD (Advisor); Orlando Simonetti, PhD (Committee Member); Elliott Crouser, MD (Committee Member); Stephen Lee, PhD (Committee Member)

Subjects:

Biomedical Engineering; Biomedical Research; Medical Imaging; Medicine

Keywords:

acute coronary syndrome; magnetic resonance imaging; magnetic resonance spectroscopy; animal model; phosphocreatine; t2 mapping

Maschino, Tyler StephenFREQUENCY-SELECTIVE DESIGN OF WIRELESS POWER TRANSFER SYSTEMS FOR CONTROLLED ACCESS APPLICATIONS
Master of Science, Miami University, 2016, Computational Science and Engineering
Wireless power transfer (WPT) has become a common way to charge or power many types of devices, ranging from cell phones to electric toothbrushes. WPT became popular through the introduction of a transmission mode known as strongly coupled magnetic resonance (SCMR). This means of transmission is non-radiative and enables mid-range WPT. Shortly after the development of WPT via SCMR, a group of researchers introduced the concept of resonant repeaters, which allows power to hop from the source to the device. These repeaters are in resonance with the WPT system, which enables them to propagate the power wirelessly with minimal losses to the environment. Resonant repeaters have rekindled the dream of ubiquitous wireless power. Inherent risks come with the realization of such a dream. One of the most prominent risks, which we set out in this thesis to address, is that of accessibility to the WPT system. We propose the incorporation of a controlled access schema within a WPT system to prevent unwarranted use of wireless power. Our thesis discusses the history of electromagnetism, examines the inception of WPT via SCMR, evaluates recent developments in WPT, and further elaborates on the controlled access schema we wish to contribute to the field.

Committee:

Dmitriy Garmatyuk, PhD (Advisor); Mark Scott, PhD (Committee Member); Herbert Jaeger, PhD (Committee Member)

Subjects:

Computer Engineering; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

Keywords:

wireless power transfer; WPT; resonance; magnetic resonance; electromagnetism; power security; power encryption; wireless power transfer security; wireless power transfer encryption; SCMR; strongly coupled magnetic resonance; power transfer;

Deshmane, Anagha VishwasPartial Volume Quantification Using Magnetic Resonance Fingerprinting
Doctor of Philosophy, Case Western Reserve University, 2017, Biomedical Engineering
Magnetic resonance imaging (MRI) is a key clinical tool which allows for imaging of biological tissues with large field-of-view, millimeter resolution, and good soft tissue contrast, without exposing the patient to ionizing radiation. Magnetic Resonance Fingerprinting (MRF) is a quantitative MRI method which pairs pseudorandom magnetization excitations and fast image acquisition with dictionary-based reconstruction for simultaneous mapping of multiple tissue and experimental properties, including T1, T2, and off-resonance, from a single experiment performed within a clinically feasible scan time. MRF signal evolutions vary in shape for different combinations of encoded properties. Like other quantitative MRI methods, MRF maps yield quantitative maps in which properties are averaged over the voxel dimensions. However, in the presence of partial volumes, voxel-averaged properties are insufficient to quantitatively assess tissue characteristics such as the potential presence of pathology. It is therefore necessary to quantify both tissue properties and voxel composition. The uniqueness of signal evolutions emanating from different tissue types in MRF allows for both tissue property mapping as well as quantification of partial volumes from the same measurement. In this dissertation, two approaches to partial volume quantification by MR Fingerprinting (PV-MRF) are quantitatively assessed for accuracy in the presence of artifacts and model errors. Applications of PV-MRF are also explored, including segmentation of pathology, improved synthetic imaging, and absolute quantification of sub-voxel tissue species.

Committee:

Mark Griswold (Advisor); Nicole Seiberlich (Committee Chair); Xin Yu (Committee Member); Erkki Somersalo (Committee Member)

Subjects:

Biomedical Engineering; Engineering; Medical Imaging; Radiology

Keywords:

magnetic resonance imaging; quantitative imaging; partial volume; absolute quantification; proton density mapping; subvoxel analysis; tissue characterization; tissue quantification; magnetic resonance fingerprinting;

Jiang, YunDEVELOPMENT OF NOVEL PULSE SEQUENCES FOR MAGNETIC RESONANCE FINGERPRINTING
Doctor of Philosophy, Case Western Reserve University, 2017, Biomedical Engineering
Quantification of tissue properties has long been a research goal in Magnetic Resonance Imaging (MRI). However, the long acquisition time of the conventional quantitative method prohibited its adoption in the clinic. The recently proposed Magnetic Resonance Fingerprinting (MRF) is a novel framework that simultaneously quantifies multiple tissue properties using pseudorandom acquisition parameters. It breaks the convention of MRI which acquires a steady- state signal with fixed acquisition parameters, and thus MRF can exploit all degrees of freedom in the pulse sequence design. With nearly unlimited choices of sequence parameters, the thesis explored and presented MRF methods based on the QUick Echo Split NMR technique (QUEST) to reduce the Specific Absorption Rate (SAR), the Fast Imaging with Steady-state Precession (FISP) to improve the performance with off-resonance, the Double Echo Steady-state (DESS) to quantify diffusion, and a Simultaneous MultiSlice (SMS) MRF to further reduce the acquisition time. The development of these novel methods improves the robustness of MRF and have the potential to extend MRF to wide ranges of applications.

Committee:

Mark Griswold, PhD (Advisor); Nicole Seiberlich, PhD (Committee Chair); Xin Yu, PhD (Committee Member); Erkki Somersalo, PhD (Committee Member); Jeffrey Sunshine, MD,PhD (Committee Member)

Subjects:

Biomedical Engineering

Keywords:

Magnetic Resonance Imaging; Magnetic Resonance Fingerprinting;T1;T2;relaxation;MRI;MRF

Fong, Kin ChungHigh Sensitivity Electron Spin Resonance by Magnetic Resonance Force Microscopy at Low Temperature
Doctor of Philosophy, The Ohio State University, 2008, Physics

This dissertation describes the development and usage of the experimental technique -- Magnetic Resonance Force Microscopy (MRFM) -- to study electron spin resonance at low temperature in sensitivity as high as two electron spins. MRFM detects magnetic resonance by sensing the small force acting on the cantilever by the paramagnetic electron spins in the sample through magnetic coupling. I have applied this technique to measure the fluctuating magnetic moments of few electron spin ensembles known as the statistical polarization or the spin noise.

In this dissertation, I describe the basic principles and setup of the MRFM experiments. I have used the MRFM experiment to verify that applying negative feedback to the cantilever can reduce the cantilever response time without sacrificing the signal-to-noise ratio in the force detection. Using the new spin manipulation scheme and the microwave resonator I designed for low temperature MRFM experiments, MRFM force spectra are measured and understood by modeling the spins undergoing magnetic resonance in an inhomogeneous magnetic field.

I have used the high sensitivity MRFM experiment to observe the real-time fluctuation of the electron spin magnetic moments. From the statistics of this fluctuation, the number of resonating spins and the correlation time of the statistical polarization are measured. I have shown that the spin correlation time is due to the one and two phonon relaxation processes in the silicon dioxide sample by measuring the spin correlation time in various sample temperature. As the fluctuating time scale of the statistical polarization is not dominated by the MRFM instrumentation processes, the measured spin correlation time can be used to enhance image contrast by the relaxation-weighted imaging.

Committee:

P. Christopher Hammel (Advisor); Thomas J. Gramila (Committee Member); Gregory P. Lafyatis (Committee Member); John W. Wilkins (Committee Member)

Subjects:

Physics

Keywords:

Magnetic Resonance Force Microscopy; Magnetic Resonance; Force Detection; High Sensitivity; Cantilever; Spin Correlation Time; Statistical Polarization; Signal Energy; Spin Noise; Low Temperature; Cantilever; Microwave resonator; silica

Lee, Kai MonSolution structures of yeast ribosomal 5S and 5.8S ribonucleic acids via 500 MHz proton nuclear magnetic resonance spectroscopy /
Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Ribosomes;Yeast;RNA;Proton magnetic resonance;Nuclear magnetic resonance spectroscopy

Liu, YuchiDEVELOPMENT OF DYNAMIC PHOSPHORUS-31 AND OXYGEN-17 MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING TECNIQUES FOR PRECLINICAL ASSESSMENT OF ENERGY METABOLISM IN VIVO
Doctor of Philosophy, Case Western Reserve University, 2018, Biomedical Engineering
Adenosine triphosphate (ATP) is the energy currency that maintains physiological activities of the cell. The major source of ATP in aerobic organisms is oxidative phosphorylation occurred in mitochondria. Disruptions of oxidative phosphorylation are associated with various metabolic diseases. Hetero-nuclei MRI plays an important role in assessing functional cell processes such as oxidative metabolism. Specifically, phosphorous-31 (31P) and oxygen-17 (17O) MRS/MRI provide a non-invasive tool to probe mitochondrial oxidative capacity and oxygen consumption, respectively. However, hetero-nuclei MRI in general is challenging due to the low in vivo concentrations and low MR sensitivity. Long acquisition time is usually required even with low spatial resolution. In this thesis, novel approaches for imaging 31P and 17O with high spatial resolution and temporal resolution were developed and demonstrated in small animals at high fields. In particular, this thesis focused on fast 31P MR Spectroscopic Imaging (MRSI) and 17O MRI approaches with non-Cartesian encoding schemes that assess mitochondrial function in skeletal muscle and cerebral oxygen metabolism/water movement across the blood-brain barrier (BBB), respectively. 15 Four projects are described in this thesis. First, an ischemia-reperfusion protocol was established to evaluate mitochondrial oxidative capacity in type 2 diabetic rats using 31P MRS. Second, a fast dynamic 31P MRSI method using a low-rank model was developed and demonstrated in rat skeletal muscle during ischemia-reperfusion. Third, a dynamic 17O MRI method using golden-angle radial acquisition combined with k-space weighted image contrast (KWIC) reconstruction was developed and validated in simulation studies and phantom experiments. Finally, the 17O MRI method was demonstrated in a mouse model with glioblastoma (GBM) to assess the water movement across BBB after a bolus in injection of 17O-labeled water. The 17O MRI approach was also applied to a mouse model of middle cerebral artery occlusion (MCAO) in 17O-labeled gas inhalation experiments to assess cerebral oxygen metabolism in vivo. The success of these studies will pave the way for fast metabolic imaging using 31P and 17O MRI techniques and allow for the assessment of metabolic alterations in various disease models, such as diabetes, ischemic stroke, etc.

Committee:

Xin Yu, Sc.D. (Advisor); Nicole Seiberlich, Ph.D. (Committee Chair); Mark Griswold, Ph.D. (Committee Member); John Kirwan, Ph.D. (Committee Member); Nicola Lai, Ph.D. (Committee Member)

Subjects:

Biomedical Engineering

Keywords:

magnetic resonance imaging, magnetic resonance spectroscopy, energy metabolism, phosphorus-31, oxygen-17

Sokol, Paul E.A study of the quadrupolar glass phase of D2 via proton NMR.
Doctor of Philosophy, The Ohio State University, 1981, Graduate School

Committee:

Not Provided (Other)

Subjects:

Physics

Keywords:

Nuclear magnetic resonance;Proton magnetic resonance;Nuclear quadrupole resonance

Adams, David GeorgeNuclear magnetic resonance studies of some Grignard reagents and organolithium compounds /
Doctor of Philosophy, The Ohio State University, 1964, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Organolithium compounds;Grignard reagents;Nuclear magnetic resonance

Baum, Robert RaySpectroscopic Studies of a Series of Co(II) ß-diketonates
Doctor of Philosophy, Miami University, 2016, Chemistry
In an extension of previous research by the Tierney group, a series of cobalt(II) ß-diketonates with clear dynamics was found in the literature for further spectroscopic studies. There are two chapters of studies on these complexes. Chapters 2 and 3 consist of nuclear magnetic resonance relaxation (NMR) studies. Chapter 2 focuses on the two complexes in the series with a bidentate amine ligand. Chapter 3 focuses on the three complexes in the series with monodentate amine ligands. The relaxation times were measured at magnetic fields of 4.7 and 7.0 T on the 19F nuclei of all five complexes and for 1H on two complexes. From these relaxation times, the electronic correlation times were extracted using a modified version of the Solomon-Bloembergen-Morgan equations that takes angles and distances into account. Optical spectroscopy was also performed to determine the Racah parameters and energy level separations of these complexes. In addition, three chapters detail other spectroscopic work performed by the author. Chapter 4 details a reexamination of the spectroscopy of a series of heteroscorpionates that provides new insight on the electron paramagnetic resonance of pseudotetrahedral Co(II). Chapter 5 discusses a trinuclear iron complex and spectroscopic evidence that the iron nuclei are antiferromagnetically coupled. Chapter 6 discusses optical and NMR spectroscopy of the Fe(II), Ni(II), and Co(II) versions of a five coordinate complex

Committee:

David Tierney (Advisor); Michael Crowder (Committee Chair); Robert McCarrick (Committee Member); Neil Danielson (Committee Member); Luis Actis (Committee Member)

Subjects:

Chemistry; Inorganic Chemistry

Keywords:

beta-diketonates; nuclear magnetic resonance; paramagnetic relaxation enhancements

Williams, Donald HowardStereochemistry of transition metal complexes.
Doctor of Philosophy, The Ohio State University, 1964, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Stereochemistry;Spectrum analysis;Nuclear magnetic resonance

Van Leuwen, Bruce GunnSubstituent parameters in polynuclear aromatic hydrocarbons /
Doctor of Philosophy, The Ohio State University, 1968, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Aromatic compounds;Nuclear magnetic resonance

Cardellino, Jeremy DDynamics of Paramagnetic Spins: A Study of Spin Defects using Magnetic Resonance Force Microscopy
Doctor of Philosophy, The Ohio State University, 2015, Physics
Magnetic Resonance Force Microscopy (MRFM) is a challenging yet incredibly sensitive tool for characterizing and imaging magnetic materials down to the nanoscale. It combines the technology of scanned probe microscopy with the powerful spectral techniques of magnetic resonance. The MRFM can measure very small spin ensembles, down to a single electron spin, and the measurements are performed at thermal equilibrium. Instead of perturbing the polarization away from equilibrium, the `spin noise' or statistical spin fluctuations are used to generate a force signal. Here I show MRFM measurements on a nanoscale `spin wire', which is a narrow, high spin density region implanted in a diamond substrate. The spin wire measurements reveal an interesting interplay between the transport and lifetime of spins con fined within the nanoscale diamond wire which are relevant for the development of nanoscale spintronics. Additionally, I show measurements which resolve the hyper fine spectrum of the defects in the spin wire by measuring less than 100 net spins.

Committee:

Chris Hammel (Advisor); Ezekiel Johnston-Halperin (Committee Member); David Stroud (Committee Member); Richard Furnstahl (Committee Member)

Subjects:

Condensed Matter Physics; Low Temperature Physics; Physics

Keywords:

MRFM;spin; spintronics; defects; lifetime; force; detection; magnetic; resonance; microscopy; dynamics; paramagnetic;

Ting, Samuel TAn Efficient Framework for Compressed Sensing Reconstruction of Highly Accelerated Dynamic Cardiac MRI
Doctor of Philosophy, The Ohio State University, 2016, Biomedical Engineering
The research presented in this work seeks to develop, validate, and deploy practical techniques for improving diagnosis of cardiovascular disease. In the philosophy of biomedical engineering, we seek to identify an existing medical problem having significant societal and economic effects and address this problem using engineering approaches. Cardiovascular disease is the leading cause of mortality in the United States, accounting for more deaths than any other major cause of death in every year since 1900 with the exception of the year 1918. Cardiovascular disease is estimated to account for almost one-third of all deaths in the United States, with more than 2150 deaths each day, or roughly 1 death every 40 seconds. In the past several decades, a growing array of imaging modalities have proven useful in aiding the diagnosis and evaluation of cardiovascular disease, including computed tomography, single photon emission computed tomography, and echocardiography. In particular, cardiac magnetic resonance imaging is an excellent diagnostic tool that can provide within a single exam a high quality evaluation of cardiac function, blood flow, perfusion, viability, and edema without the use of ionizing radiation. The scope of this work focuses on the application of engineering techniques for improving imaging using cardiac magnetic resonance with the goal of improving the utility of this powerful imaging modality. Dynamic cine imaging, or the capturing of movies of a single slice or volume within the heart or great vessel region, is used in nearly every cardiac magnetic resonance imaging exam, and adequate evaluation of cardiac function and morphology for diagnosis and evaluation of cardiovascular disease depends heavily on both the spatial and temporal resolution as well as the image quality of the reconstruction cine images. This work focuses primarily on image reconstruction techniques utilized in cine imaging; however, the techniques discussed are also relevant to other dynamic and static imaging techniques based on cardiac magnetic resonance. Conventional segmented techniques for cardiac cine imaging require breath-holding as well as regular cardiac rhythm, and can be time-consuming to acquire. Inadequate breath-holding or irregular cardiac rhythm can result in completely non-diagnostic images, limiting the utility of these techniques in a significant patient population. Real-time single-shot cardiac cine imaging enables free-breathing acquisition with significantly shortened imaging time and promises to significantly improve the utility of cine imaging for diagnosis and evaluation of cardiovascular disease. However, utility of real-time cine images depends heavily on the successful reconstruction of final cine images from undersampled data. Successful reconstruction of images from more highly undersampled data results directly in images exhibiting finer spatial and temporal resolution provided that image quality is sufficient. This work focuses primarily on the development, validation, and deployment of practical techniques for enabling the reconstruction of real-time cardiac cine images at the spatial and temporal resolutions and image quality needed for diagnostic utility. Particular emphasis is placed on the development of reconstruction approaches resulting in with short computation times that can be used in the clinical environment. Specifically, the use of compressed sensing signal recovery techniques is considered; such techniques show great promise in allowing successful reconstruction of highly undersampled data. The scope of this work concerns two primary topics related to signal recovery using compressed sensing: (1) long reconstruction times of these techniques, and (2) improved sparsity models for signal recovery from more highly undersampled data. Both of these aspects are relevant to the practical application of compressed sensing techniques in the context of improving image reconstruction of real-time cardiac cine images. First, algorithmic and implementational approaches are proposed for reducing the computational time for a compressed sensing reconstruction framework. Specific optimization algorithms based on the fast iterative/shrinkage algorithm (FISTA) are applied in the context of real-time cine image reconstruction to achieve efficient per-iteration computation time. Implementation within a code framework utilizing commercially available graphics processing units (GPUs) allows for practical and efficient implementation directly within the clinical environment. Second, patch-based sparsity models are proposed to enable compressed sensing signal recovery from highly undersampled data. Numerical studies demonstrate that this approach can help improve image quality at higher undersampling ratios, enabling real-time cine imaging at higher acceleration rates. In this work, it is shown that these techniques yield a holistic framework for achieving efficient reconstruction of real-time cine images with spatial and temporal resolution sufficient for use in the clinical environment. A thorough description of these techniques from both a theoretical and practical view is provided -- both of which may be of interest to the reader in terms of future work.

Committee:

Orlando P. Simonetti, PhD (Advisor); Lee C. Potter, PhD (Committee Member); Rizwan Ahmad, PhD (Committee Member); Jun Liu, PhD (Committee Member)

Subjects:

Applied Mathematics; Electrical Engineering; Health; Health Care; Medical Imaging; Medicine; Radiology; Scientific Imaging

Keywords:

cardiac magnetic resonance; real time cardiac cine; image reconstruction; signal recovery; sparsity models; compressed sensing; parallel imaging; FISTA; Gadgetron; optimization; nonlinear; fast imaging; accelerated; GPU; graphics processing unit

Parrish, Jason ThomasInvestigations into Multiple–Herbicide-Resistant Ambrosia artemisiifolia (Common Ragweed) in Ohio and Glyphosate-Resistance Mechanisms
Doctor of Philosophy, The Ohio State University, 2015, Horticulture and Crop Science
Common ragweed (Ambrosia artemisiifolia) is a weed problem in many places throughout the world. Though it seldom dominates the landscape, common ragweed seems to be able to exploit diverse habitats. Common ragweed is primarily outcrossing and has a high rate of gene polymorphisms, leading to high genetic diversity. This high level of genetic diversity likely plays a major role in the evolution of herbicide-resistant biotypes. Whole-plant bioassays of herbicide dose-response in the greenhouse were used to characterize resistance levels to glyphosate, cloransulam-methyl, and fomesafen herbicides. Additional studies were conducted to provide insight into potential mechanisms that may contribute to the development of resistance to glyphosate in an Ohio ragweed biotype, including 5 enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene sequencing, quantitative PCR of the EPSPS gene, EPSPS enzyme immunoblot and activity/inhibition assays, 31P nuclear magnetic resonance (NMR) studies of glyphosate-treated tissues, and whole-plant absorption and translocation studies using 14C-labeled glyphosate. A single common ragweed population from Clinton County, Ohio exhibited multiple resistance to herbicides at dosages that exceeded the rate required to kill herbicide-sensitive common ragweed biotypes from 4- to 30 fold for glyphosate, > 1000 fold for cloransulam-methyl, and 14- to > 100 fold for fomesafen. This is the first report of a common ragweed biotype with multiple resistance to herbicides from three site-of-action (SOA) groups. Sequencing data indicated the gene coding for EPSPS has a high mutation rate in all studied common ragweed biotypes, but it typically does not code for an altered amino acid sequence in the glyphosate binding area. Additional studies identified alleles of EPSPS coding for proline-to-serine and proline-to-threonine substitutions at amino acid number 106 (based upon the mature maize EPSPS numbering scheme). Previous studies by other authors have found these amino acid substitutions to confer glyphosate resistance in numerous other species. The alleles containing these mutations were not detected in previous studies of Ohio ragweed populations, and it is not known whether these alleles are translated into a functional EPSPS protein. Direct sequence analysis also suggested that there are six-to-eight or more partial- or full-length copies of the EPSPS gene in a typical diploid (2n) common ragweed plant. An immunoblot assay with common ragweed total soluble protein, as well as Palmer amaranth (Amaranthus palmeri) glyphosate-sensitive and EPSPS overexpressing glyphosate-resistant controls, showed a single plant from the glyphosate-resistant biotype with increased EPSPS expression. Quantitative PCR also showed an increased relative EPSPS gene copy number in the same plant. 31P NMR data showed similar uptake of glyphosate into the leaf cells and no vacuolar sequestration in all common ragweed biotypes, with lower sugar-phosphate (including shikimate-3-phosphate) accumulation relative to glyphosate-susceptible common ragweed plants. Similarly, absorption and translocation of 14C-labeled glyphosate over 48 hours did not differ between resistant and susceptible biotypes. More research will be required to unequivocally determine the molecular basis of glyphosate resistance in common ragweed, but accumulated evidence supports the hypothesis that multiple mechanisms of glyphosate resistance are possible within a common ragweed population.

Committee:

Mark Loux (Advisor); S. Kent Harrison (Committee Member); David Mackey (Committee Member); James Metzger (Committee Member); Anne Dorrance (Committee Member)

Subjects:

Agricultural Chemicals; Agriculture; Agronomy; Molecular Biology; Plant Biology

Keywords:

Ambrosia artemisiifolia; common ragweed; glyphosate; resistance; immunoblot; dose-response; fomesafen; cloransulam-methyl; 5-enolpyruvylshikimate-3-phosphate synthase; EPSPS; translocation; 31P nuclear magnetic resonance; NMR; PCR

Goodpaster, Aaron M.Statistical Analysis Methods Development for Nuclear Magnetic Resonance and Liquid Chromatography/Mass Spectroscopy Based Metabonomics Research
Doctor of Philosophy, Miami University, 2011, Chemistry
This dissertation describes new statistical analysis methods for nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography/mass spectroscopy (LC/MS) – based metabonomics along with determining if diapers and cotton balls could introduce contamination into newborn babies urine when collecting their urine for metabonomic studies using the “cotton ball in diaper” method of collection. Chapter 1 provides a background of metabonomics along with the advantages and disadvantages of the two analytical techniques used, NMR and LC/MS, along with how the data is analyzed using multivariate data analysis. Chapter 2 develops a decision tree algorithm to determine which buckets in the loadings plot are statistically significant in the principal component analysis (PCA). After the statistical analysis the loadings plot was colored based on a “heat-map” according to the p-score for each loading, which showed how significant the buckets were in the analysis. Based on the significance analysis, the effect size was calculated to allow for the calculation of the study size that is needed for each group in a metabonomics study. Chapter 3 develops a metric for quantification of cluster separation and for assessment of the statistical significance of cluster separation seen in the scores plot of the PCA. Along with this it was shown how Pareto scaling and partial least squares – discriminant analysis (PLS-DA) affected the separation in the scores plot, along with how it affects the loadings plot of a PCA. Chapter 4 investigated the coefficient of variation (CV) of NMR data collected over an eight-month period and how the signal-to-noise (S/N) ratio affected the CV. This study determined that the CV has no relation to the S/N ratio and that the CV must be considered when validating a potential biomarker. Chapter 5 investigates the potential effect of diaper and cotton ball contamination on NMR and LC/MS-based metabonomic studies of urine from newborn babies. It was determined that the diaper could potentially affect a metabonomic study, but when the cotton ball is inserted the chance for contamination decreases. Chapter 6 summarizes the presented research.

Committee:

Michael A. Kennedy, PhD (Advisor); Neil D. Danielson, PhD (Committee Chair); Carole Dabney-Smith, PhD (Committee Member); Blanton S. Tolbert, PhD (Committee Member); Natosha L. Finley, PhD (Committee Member)

Subjects:

Analytical Chemistry; Biostatistics; Chemistry

Keywords:

Metabonomics; Statistical Analysis; Nuclear Magnetic Resonance; Liquid Chromatography; Mass Spectroscopy; NMR; LC/MS

Lee, InheeNanoscale Ferromagnetic Resonance Imaging using Magnetic Resonance Force Microscopy
Doctor of Philosophy, The Ohio State University, 2010, Physics
Nanoscale patterned magnetic structures and multi-component magnetic devices have been studied actively for applications of highly efficient data storage and non-volatile magnetic memory devices. Those studies demand high resolution magnetic imaging tools which can characterize complex, often buried nanoscale structures. Ferromagnetic Resonance (FMR) is a powerful spectroscopic tool which provides the magnetic characterizing parameters of spectroscopically identified magnetic materials with high precision. However, FMR studies of nanoscale samples are limited due to insufficient sensitivity and lack of imaging capabilities. Scanned probe FMR using Magnetic Resonance Force Microscopy (MRFM) is an excellent tool for understanding nanoscale ferromagnetic structures based on its high sensitivity and high resolution. Non-interacting electron and nuclear spins in MRFM can be excited selectively in the thin sensitive slice defined by the high magnetic field gradient of the magnetic probe tip. The sensitive slice as a probe enables high resolution three-dimensional imaging. However, for ferromagnets, the mechanism for magnetic resonance imaging is quite different due to the strong spin-spin interactions which lead to collective spin wave excitation. Our recent studies of Ferromagnetic Resonance Force Microscopy (FMRFM) have shown that the magnetic probe tip not only detects the FMRFM force, but also perturbs FMR modes, and even distorts or spatially localizes FMR modes using the strongly inhomogeneous probe field. This strong perturbation of probe field enables us to achieve and image quantitative magnetic information in the local region of ferromagnetic structures. In this thesis I will present various FMRFM imaging techniques using the strong inhomogeneous magnetic field of the micromagnetic probe tip. First, FMRFM imaging in a weak probe field will be discussed. In this case, the shapes of magnetostatic modes in FMR are determined by a confined sample structure while the effect of probe field is ignorable. However, FMR peak positions are shifted by the probe field, which allows encoding of the spatial mode profile of magnetostatic modes into FMR resonance field. On the other hand, in a strong probe field, the shapes of FMR modes can be distorted or spatially localized. In particular, localized modes are suitable for FMRFM imaging which provides a map of intrinsic magnetic properties existing within the local area of the sample. Concerning these localized modes, I will present our recent observations, quantitative analysis and their application for FMR imaging with high field sensitivity of the internal field in a ferromagnetic film . Furthermore, I will discuss other quantitative local magnetic characterization methods such as magnetic force microscopy (MFM) induced by a strong inhomogeneous probe tip field and suppressed or distorted FMR modes FMRFM.

Committee:

Chris Hammel (Advisor); Jay Gupta (Committee Member); David Stroud (Committee Member); Louis DiMauro (Committee Member)

Subjects:

Physics

Keywords:

FMR; MRFM; FMRFM; magnetic resonance; imaging; probe field; localized modes

KAIMAL, VINODIn VivoMR Microscopy of Tumor Targeted Liposome Combining USPIO and Saposin-C
PhD, University of Cincinnati, 2007, Engineering : Biomedical Engineering
In recent years, molecular imaging, defined as the visualization of biologic process in vivoat the molecular level, has gained prominence in the detection and monitoring of cancerous tissue. Several targets for the molecular imaging of cancer have been identified but in order to produce selective contrast enhancement, target specific contrast agent delivery methods and optimized imaging techniques need to be developed. This dissertation describes a molecular imaging approach that uses liposomes loaded with Ultra-small Super-Paramagnetic Iron Oxide (USPIO) nanoparticles targeted to tumor cells. Liposomes made from dioleylphosphatidylserine, (DOPS) are being used as carriers for Saposin-C, a fusogenic protein, currently being investigated for its effect in inducing cell death in a variety of human cancer cells. We developed an efficient method for loading Saposin-C-DOPS liposomes with USPIO. Further, we tested the uptake and MR detectability of these contrast-laden liposomes, referred to as ScDOPS-IO, in vitroin tumor cell cultures. Finally, we evaluated the feasibility of detecting ScDOPS-IO liposomes using MR imaging in vivo. The ScDOPS-IO liposomes encapsulated an average of 94.8±12.8 µg Fe /ml when a 1:30 molar ratio of saposin-C to DOPS was used with 1 mM DOPS and exhibited a transverse relaxivity (r2) of 101.21±4.9 mM-1s-1. Uptake in tumor cell cultures was found to be proportional to both time of exposure and initial concentration of ScDOPS-IO in growth medium. The cells were MR detectable against a uniform agarose background when average encapsulation was greater that 1 pg Fe/cell, using high resolution T2* weighted MR imaging. In vivoexperiments indicate accumulation of ScDOPS-IO in tumor xenografts in mice and T2 mapping of the xenografts show a significant drop in mean tumor T2 about 4 hours post injection of ScDOPS-IO. These results demonstrate the feasibility of using MR imaging for quantitative estimation of delivery and uptake of targeted drugs and early detection of tumors using targeted contrast agents. The methods presented here are promising for translation to applications in human subjects for clinical trials of new chemotherapy drugs.

Committee:

Scott Holland (Advisor)

Subjects:

Engineering, Biomedical

Keywords:

USPIO; Saposin-C; liposome; magnetic resonance imaging; MRI

Dudley, Jonathan A.Phosphorus-31 Magnetic Resonance Spectroscopy Quantification Methods for the Characterization of Brain Bioenergetics in Bipolar Disorder Subjects
PhD, University of Cincinnati, 2012, Engineering and Applied Science: Biomedical Engineering

Phosphorus-31 magnetic resonance spectroscopy (31P MRS) has long been successfully employed in studies of energy metabolism and in particular for investigations of brain bioenergetics in psychiatric disorders. Simple quantification of the 31P spectra yields information about the relative concentrations of the metabolites phosphocreatine (PCr), adenosine triphosphate (ATP), phosphomonoesters (PME), phosphodiesters (PDE), and inorganic phosphate (Pi). This work utilized more sophisticated methods of 31P quantification to investigate the pathophysiology of bipolar disorder (BD). Specifically, three-dimensional 31P MRS imaging (MRSI) data was combined with single-voxel proton (1H) MRS data and high resolution anatomical imaging data to indirectly determine concentrations of adenosine diphosphate ([ADP]) and magnesium ([Mg2+]). Additionally, tissue regression analyses provided estimates of [PCr], [ATP], [PME], [PDE], [Pi], [Mg2+], and intracellular pH (pHi) in pure white matter (WM) and gray matter (GM).

Findings from numerous 31P MRS and 1H MRS studies of BD have culminated into a hypothesis of mitochondrial dysfunction underlying the pathophysiology of the disease. Results from this work provide new evidence in support of this hypothesis. Manic BD subjects displayed lower pHi (7.01 ¿¿¿¿ 0.04) and [ADP] (20.51 ¿¿¿¿ 8.70 ¿¿¿¿M) compared to controls (7.06 ¿¿¿¿ 0.07 and 33.73 ¿¿¿¿ 13.20 ¿¿¿¿M) in the anterior cingulate cortex (ACC). Euthymic BD subjects were found to have increased choline concentrations (2.10 ¿¿¿¿ 0.26 mM) and decreased [ADP] (15.16 ¿¿¿¿ 5.22 ¿¿¿¿M) in the ACC and left ventral lateral prefrontal cortex, respectively, relative to controls (1.73 ¿¿¿¿ 0.18 mM and 27.43 ¿¿¿¿ 12.76 ¿¿¿¿M). Collectively these results indicate mitochondrial dysfunction in both manic and euthymic BD subjects by suggesting a shift toward glycolysis, impaired energy production, and altered phospholipid metabolism.

Another, but not mutually exclusive, theory surrounding BD is that of anterior limbic network disruption. Diffusion tensor imaging (DTI) studies have consistently revealed WM abnormalities in BD, but the limited spatial resolution of traditional 31P spectroscopic techniques has precluded any substantive conclusions from being drawn about the bioenergetic environment of WM in BD. However, the tissue regression analysis of 31P MRSI data combined with imaging data in this work revealed significant differences in numerous metabolites in pure WM of BD subjects relative to controls. Manic and euthymic subjects had lower estimated [ATP] (3.56 ¿¿¿¿ 0.23 mM, 3.62 ¿¿¿¿ 0.36 mM), [PDE] (2.19 ¿¿¿¿ 0.34 mM, 2.36 ¿¿¿¿ 0.20 mM), and [Pi] (1.65 ¿¿¿¿ 0.14 mM, 1.74 ¿¿¿¿ 0.28 mM) in pure WM relative to controls (4.38 ¿¿¿¿ 0.26 mM, 3.24 ¿¿¿¿ 0.33 mM, and 2.37 ¿¿¿¿ 0.22 mM). These results support the model of anterior limbic network disruption suggested by the findings of decreased fractional anisotropy from DTI studies and also indicate that mitochondrial dysfunction and other yet-hypothesized mechanisms may characterize the pathophysiology of the disease.

Committee:

Jing-Huei Lee, PhD (Committee Chair); Richard Komoroski, PhD (Committee Member); William Ball, MD (Committee Member); T. Douglas Mast, PhD (Committee Member)

Subjects:

Biomedical Research

Keywords:

Magnetic Resonance Spectroscopy;Phosphorus-31;Bipolar Disorder;Quantification;Bioenergetics;;

Stanley, Daniel CMAGNETIC DAMPING IN FE3O4 THROUGH THE VERWEY TRANSITION FOR VARIABLE AG THICKNESSES
Master of Science, Miami University, 2013, Physics
The temperature dependence of damping in epitaxial Fe3O4/Ag bilayers grown on [001] MgO substrates was measured by Ag thickness. The Fe3O4 was deposited to 350 nm while the Ag thickness ranged from 0 to 500 nm. Measurements using ferromagnetic resonance (FMR) at 9.5 GHz with the sample film normal to the applied magnetic field were taken over a temperature range of 80 to 295 K. In-plane FMR was also done at 35GHz to determine the anisotropy. From these measurements the effective magnetization was calculated and with it the anisotropy parameters K4 and Ku. The samples exhibited easy-plane anisotropy consistent with thin-film effects. Line widths did not change substantially until the Verway transition (TV ~ 110 K), after which the damping increases dramatically at lower temperatures. This phenomenon will be discussed in terms of spin pumping into the Ag in conjunction with the properties of Fe3O4 changing at the Verway transition.

Committee:

Michael Pechan (Advisor); Herbert Jaeger (Committee Member); Jennifer Blue (Committee Member)

Subjects:

Physics

Keywords:

Magnetite; Magnetic Resonance; Spin injected currents; Thin films; Magnetism

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