Author: Ashish RajPublisher:
ISBN:
Category :
Languages : en
Pages : 302
Book Description
Improvements in Magnetic Resonance Imaging Using Information Redundancy
Author: Ashish RajFast Dynamic Magnetic Resonance Imaging Using Sparse Recovery Methods and Novel Signal Encoding Formulations
Author: Vimal SinghPublisher:
ISBN:
Category :
Languages : en
Pages : 336
Book Description
Magnetic resonance imaging (MRI) is a non-invasive imaging modality that provides excellent soft tissue contrast without using ionizing radiations. These qualities/properties make MRI the preferred imaging modality for critical organs like heart and brain. Over the past decade, the advancement in hardware and image reconstruction algorithms has led to substantial improvements in MRI in terms of imaging speeds, quality and reliability. However, MRI speeds need to be further improved while retaining/maintaining the image quality given that the emerging medical diagnostic procedures are increasingly relying on detailed characterization of physiological functions that evolve on time scales too fast to be captured using conventional MRI methods. This dissertation starts with presenting a sparse signal recovery based fast MRI method. This method synergistically combines a data redundancy scheme for high frequency details with a novel and physically realizable MR signal encoding formulation. The new signal encoding formulation uses clinically deployed tagging radio frequency pulses to mix information in the spatial frequency domain prior to acquisition. Thus, the new formulation leads to a more uniform coverage of spatial frequency information even at high accelerations. The synergistic combination of image-detail redundancy encoding with tagging based signal encoding allows recovery of edges and fine structures with unprecedented quality. Next, this dissertation evaluates the use of fast spiral trajectories for high spatial resolution functional imaging of human superior colliculus. Gradient efficient and motion-robust spiral trajectories are used to keep fMRI scan durations short. . However, high resolution imaging of human subcortical structures using these trajectories is limited due to the weak functional responses of SC structures and also low signal-to-noise ratio associated with small voxels. To improve the functional sensitivity of spiral trajectories, dual echo variants are used. Combination of two echoes of the dual-echo variants reduces noise and thereby improves the functional sensitivity of high resolution fMRI. Lastly, this dissertation presents a novel formulation for fast dynamic MRI which combines the generic linear dynamical system model with sparse recovery techniques. Specifically, the formulation uses a known prior spatio-temporal model to predict the underlying image and uses sparse recovery techniques to recover the residual image. The spatio-temporal evolution model inherently encodes for coupled data redundancies in the spatial- and temporal-dimensions. Also, the generalizability of the formulation in choosing the evolution model allows it to be applicable to various physiological functions.
Accelerated Acquisition of Quantitative MRI Using Parametric Redundancy
Author: Karthik Rao AroorPublisher:
ISBN:
Category :
Languages : en
Pages : 94
Book Description
Magnetic Resonance Imaging (MRI) is a non-invasive technique that can be utilized to obtain Quantitative T1 images of the brain. Unfortunately, the acquisition of Quantitative MRI (Q-MRI) is an extremely slow process, and this has prevented applications of Q-MRI in many clinical situations where low scan times are critical. Current approaches to speed up the acqui- sition of Q-MRI are inadequate and result in images that have artifacts. This thesis develops and validates novel compressed sensing algorithms that exploit information in spatial and para- metric dimensions for improved MRI T1 mapping. In the first project, two different sampling patterns are used to acquire MRI data at multiple Flip Angles (FAs). The two sampling patterns are the traditional stack-of-stars (SOS) and the recently introduced vastly undersampled isotropic projection (VIPR). It is shown that when used in parametric dimension regularized compressed sensing algorithms, at high accelera- tions, VIPR outperforms SOS when estimating T1 maps. The second project considers the Inversion Recovery acquisition, in which data is acquired at multiple inversion time points. Here, a novel parametric dimension compressed sensing regularizer, Total Generalized Variation (TGV) is developed, and for this data, it is shown that using TGV as a regularizer yields better T1 estimates than the current approach, which uses no regularization. TGV also outperforms the classical Total Variation (TV) regularizer by eliminating its well known staircase artifacts. In addition to continuous signals, it is also shown that TGV works well on discontinuous signals, since it does not oversmooth the discontinuities. In the third project, we develop and validate a novel technique to estimate the T1 values of all voxels in the brain simultaneously using a Total Variation (TV) regularizer, and show that this outperforms the current approach of estimating T1 values of all voxels independently. Three different approaches to perform TV based T1 estimation are proposed, and simulations are performed to determine the best one.
New Advances in Magnetic Resonance Imaging
Author: Denis LarriveePublisher: BoD – Books on Demand
ISBN: 1837691924
Category : Medical
Languages : en
Pages : 178
Book Description
Fluorine Magnetic Resonance Imaging
Author: Ulrich FlogelPublisher: CRC Press
ISBN: 1315340933
Category : Medical
Languages : en
Pages : 426
Book Description
Over the past decade, fluorine (19F) magnetic resonance imaging (MRI) has garnered significant scientific interest in the biomedical research community owing to the unique properties of fluorinated materials and the 19F nucleus. Fluorine has an intrinsically sensitive nucleus for MRI. There is negligible endogenous 19F in the body and thus there is no background signal. Fluorine-containing compounds are ideal tracer labels for a wide variety of MRI applications. Moreover, the chemical shift and nuclear relaxation rate can be made responsive to physiology via creative molecular design. This book is an interdisciplinary compendium that details cutting-edge science and medical research in the emerging field of 19F MRI. Edited by Ulrich Flögel and Eric Ahrens, two prominent MRI researchers, this book will appeal to investigators involved in MRI, biomedicine, immunology, pharmacology, probe chemistry, and imaging physics.
Ultra-Low Field Nuclear Magnetic Resonance
Author: Robert Kraus Jr.Publisher: Oxford University Press
ISBN: 0199796513
Category : Medical
Languages : en
Pages : 266
Book Description
This book is designed to introduce the reader to the field of NMR/MRI at very low magnetic fields, from milli-Tesla to micro-Tesla, the ultra-low field (ULF) regime. The book is focused on applications to imaging the human brain, and hardware methods primarily based upon pre-polarization methods and SQUID-based detection. The goal of the text is to provide insight and tools for the reader to better understand what applications are best served by ULF NMR/MRI approaches. A discussion of the hardware challenges, such as shielding, operation of SQUID sensors in a dynamic field environment, and pulsed magnetic field generation are presented. One goal of the text is to provide the reader a framework of understanding the approaches to estimation and mitigation of low signal-to-noise and long imaging time, which are the main challenges. Special attention is paid to the combination of MEG and ULF MRI, and the benefits and challenges presented by trying to accomplish both with the same hardware. The book discusses the origin of unique relaxation contrast at ULF, and special considerations for image artifacts and how to correct them (i.e. concomitant gradients, ghost artifacts). A general discussion of MRI, with special consideration to the challenges of imaging at ULF and unique opportunities in pulse sequences, is presented. The book also presents an overview of some of the primary applications of ULF NMR/MRI being pursued.
Pitfalls in Diagnostic Radiology
Author: Wilfred C. G. PehPublisher: Springer
ISBN: 3662441691
Category : Medical
Languages : en
Pages : 545
Book Description
The practice of diagnostic radiology has become increasingly complex, with the use of numerous imaging modalities and division into many subspecialty areas. It is becoming ever more difficult for subspecialist radiologists, general radiologists, and residents to keep up with the advances that are occurring year on year, and this is particularly true for less familiar topics. Failure to appreciate imaging pitfalls often leads to diagnostic error and misinterpretation, and potential medicolegal problems. This textbook, written by experts from reputable centers across the world, systematically and comprehensively highlights the pitfalls that may occur in diagnostic radiology. Both pitfalls specific to different modalities and techniques and those specific to particular organ systems are described with the help of numerous high-quality illustrations. Recognition of these pitfalls is crucial in helping the practicing radiologist to achieve a more accurate diagnosis.
Improvement in High Acceleration Parallel Magnetic Resonance Imaging Using Efficient Graph-based Energy Minimization Methods
Author: Gurmeet SinghMR and CT Perfusion and Pharmacokinetic Imaging: Clinical Applications and Theoretical Principles
Author: Roland BammerPublisher: Lippincott Williams & Wilkins
ISBN: 1469889625
Category : Medical
Languages : en
Pages : 2558
Book Description
Essential reading for both clinicians and researchers, this comprehensive resource covers what you need to know about the basic principles of perfusion, as well as its many clinical applications. Broad coverage outlines the overarching framework that interlinks methods such as DSC, DCE, CTP, and ASL. International experts in the field demonstrate how perfusion and pharmacokinetic imaging can be effectively used to analyze medical conditions, helping you reach accurate diagnoses and monitor disease progression and response to therapy.
Electromagnetics in Magnetic Resonance Imaging
Author: Christopher M. CollinsPublisher: Morgan & Claypool Publishers
ISBN: 1681740834
Category : Medical
Languages : en
Pages : 82
Book Description
In the past few decades, Magnetic Resonance Imaging (MRI) has become an indispensable tool in modern medicine, with MRI systems now available at every major hospital in the developed world. But for all its utility and prevalence, it is much less commonly understood and less readily explained than other common medical imaging techniques. Unlike optical, ultrasonic, X-ray (including CT), and nuclear medicine-based imaging, MRI does not rely primarily on simple transmission and/or reflection of energy, and the highest achievable resolution in MRI is orders of magnitude smaller that the smallest wavelength involved. In this book, MRI will be explained with emphasis on the magnetic fields required, their generation, their concomitant electric fields, the various interactions of all these fields with the subject being imaged, and the implications of these interactions to image quality and patient safety. Classical electromagnetics will be used to describe aspects from the fundamental phenomenon of nuclear precession through signal detection and MRI safety. Simple explanations and Illustrations combined with pertinent equations are designed to help the reader rapidly gain a fundamental understanding and an appreciation of this technology as it is used today, as well as ongoing advances that will increase its value in the future. Numerous references are included to facilitate further study with an emphasis on areas most directly related to electromagnetics.