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Mri Techniques For Quantitative And Microstructure Imaging
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Author :Zijing Dong (Scientist in electrical engineering and computer science) Publisher : ISBN 13 : Total Pages :0 pages Book Rating :4.:/5 (134 download)
Book Synopsis MRI Techniques for Quantitative and Microstructure Imaging by : Zijing Dong (Scientist in electrical engineering and computer science)
Download or read book MRI Techniques for Quantitative and Microstructure Imaging written by Zijing Dong (Scientist in electrical engineering and computer science) and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability to map brain microstructures such as axonal fibers and myelin content is critical in improving our understanding of brain organization and neurological diseases. Quantitative MRI has been proved with its high sensitivity to microstructures, providing a safe, non-invasive approach for human in vivo imaging. However, quantitative MRI typically requires the acquisition of multiple images for biophysical model fitting, which leads to long scan time that consequently causes low SNR, low spatial resolution, image artifacts and vulnerability to motion.
Book Synopsis Quantitative Magnetic Resonance Imaging by : Nicole Seiberlich
Download or read book Quantitative Magnetic Resonance Imaging written by Nicole Seiberlich and published by Academic Press. This book was released on 2020-11-18 with total page 1094 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantitative Magnetic Resonance Imaging is a ‘go-to’ reference for methods and applications of quantitative magnetic resonance imaging, with specific sections on Relaxometry, Perfusion, and Diffusion. Each section will start with an explanation of the basic techniques for mapping the tissue property in question, including a description of the challenges that arise when using these basic approaches. For properties which can be measured in multiple ways, each of these basic methods will be described in separate chapters. Following the basics, a chapter in each section presents more advanced and recently proposed techniques for quantitative tissue property mapping, with a concluding chapter on clinical applications. The reader will learn: The basic physics behind tissue property mapping How to implement basic pulse sequences for the quantitative measurement of tissue properties The strengths and limitations to the basic and more rapid methods for mapping the magnetic relaxation properties T1, T2, and T2* The pros and cons for different approaches to mapping perfusion The methods of Diffusion-weighted imaging and how this approach can be used to generate diffusion tensor maps and more complex representations of diffusion How flow, magneto-electric tissue property, fat fraction, exchange, elastography, and temperature mapping are performed How fast imaging approaches including parallel imaging, compressed sensing, and Magnetic Resonance Fingerprinting can be used to accelerate or improve tissue property mapping schemes How tissue property mapping is used clinically in different organs Structured to cater for MRI researchers and graduate students with a wide variety of backgrounds Explains basic methods for quantitatively measuring tissue properties with MRI - including T1, T2, perfusion, diffusion, fat and iron fraction, elastography, flow, susceptibility - enabling the implementation of pulse sequences to perform measurements Shows the limitations of the techniques and explains the challenges to the clinical adoption of these traditional methods, presenting the latest research in rapid quantitative imaging which has the possibility to tackle these challenges Each section contains a chapter explaining the basics of novel ideas for quantitative mapping, such as compressed sensing and Magnetic Resonance Fingerprinting-based approaches
Book Synopsis Application of Diffusion Microstructure Imaging in Musculoskeletal Radiology - Translation from Head to Shoulders by : Alexander Rau
Download or read book Application of Diffusion Microstructure Imaging in Musculoskeletal Radiology - Translation from Head to Shoulders written by Alexander Rau and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Objectives Quantitative MRI techniques, such as diffusion microstructure imaging (DMI), are increasingly applied for advanced tissue characterization. We determined its value in rotator cuff (RC) muscle imaging by studying the association of DMI parameters to isometric strength and fat fraction (FF). Methods Healthy individuals prospectively underwent 3T-MRI of the shoulder using DMI and chemical shift encoding-based water-fat imaging. RC muscles were segmented and quantitative MRI metrics (V-ISO, free fluid; V-intra, compartment inside of muscle fibers; V-extra, compartment outside of muscle fibers, and FF) were extracted. Isometric shoulder strength was quantified using specific clinical tests. Sex-related differences were assessed with Student's t. Association of DMI-metrics, FF, and strength was tested. A factorial two-way ANOVA was performed to compare the main effects of sex and external/internal strength-ratio and their interaction effects on quantitative imaging parameters ratios of infraspinatus/subscapularis. Results Among 22 participants (mean age: 26.7 ± 3.1 years, 50% female, mean BMI: 22.6 ± 1.9 kg/m2), FF of the individual RC muscles did not correlate with strength or DMI parameters (all p > 0.05). Subjects with higher V-intra (r = 0.57 to 0.87, p 0.01) and lower V-ISO (r = −0.6 to −0.88, p 0.01) had higher internal and external rotation strength. Moreover, V-intra was higher and V-ISO was lower in all RC muscles in males compared to female subjects (all p 0.01). There was a sex-independent association of external/internal strength-ratio with the ratio of V-extra of infraspinatus/subscapularis (p = 0.02).brbrConclusionsbrQuantitative DMI parameters may provide incremental information about muscular function and microstructure in young athletes and may serve as a potential biomarker.brbrKey Pointsbr• Diffusion microstructure imaging was successfully applied to non-invasively assess the microstructure of rotator cuff muscles in healthy volunteers.br
Book Synopsis Techniques for in Vivo High-resolution MR Imaging of Connective Tissue Microstructure by : Hee Kwon Song
Download or read book Techniques for in Vivo High-resolution MR Imaging of Connective Tissue Microstructure written by Hee Kwon Song and published by . This book was released on 1999 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quantitative MRI of the Brain by : Mara Cercignani
Download or read book Quantitative MRI of the Brain written by Mara Cercignani and published by CRC Press. This book was released on 2018-01-12 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building on the success of the first edition of this book, the winner of the 2004 British Medical Association Radiology Medical Book Competition, Quantitative MRI of the Brain: Principles of Physical Measurement gives a unique view on how to use an MRI machine in a new way. Used as a scientific instrument it can make measurements of a myriad of physical and biological quantities in the human brain and body. For each small tissue voxel, non-invasive information monitors how tissue changes with disease and responds to treatment. The book opens with a detailed exposition of the principles of good practice in quantification, including fundamental concepts, quality assurance, MR data collection and analysis and improved study statistical power through minimised instrumental variation. There follow chapters on 14 specific groups of quantities: proton density, T1, T2, T2*, diffusion, advanced diffusion, magnetisation transfer, CEST, 1H and multi-nuclear spectroscopy, DCE-MRI, quantitative fMRI, arterial spin-labelling and image analysis, and finally a chapter on the future of quantification. The physical principles behind each quantity are stated, followed by its biological significance. Practical techniques for measurement are given, along with pitfalls and examples of clinical applications. This second edition of this indispensable 'how to' manual of quantitative MR shows the MRI physicist and research clinician how to implement these techniques on an MRI scanner to understand more about the biological processes in the patient and physiological changes in healthy controls. Although focussed on the brain, most techniques are applicable to characterising tissue in the whole body. This book is essential reading for anyone who wants to use the gamut of modern quantitative MRI methods to measure the effects of disease, its progression, and its response to treatment. Features: The first edition was awarded the book prize for Radiology by the British Medical Association in 2004 Written by an authority in the field: Professor Tofts has an international reputation for quantification in MRI Gives specific ‘how to’ information for implementation of MRI measurement sequence techniques
Book Synopsis Quantifying Morphology and Physiology of the Human Body Using MRI by : L. Tugan Muftuler
Download or read book Quantifying Morphology and Physiology of the Human Body Using MRI written by L. Tugan Muftuler and published by CRC Press. This book was released on 2013-05-02 with total page 529 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the medical imaging field, clinicians and researchers are increasingly moving from the qualitative assessment of printed images to the quantitative evaluation of digital images since the quantitative techniques often improve diagnostic accuracy and complement clinical assessments by providing objective criteria. Despite this growing interest, the field lacks a comprehensive body of knowledge. Filling the need for a complete manual on these novel techniques, Quantifying Morphology and Physiology of the Human Body Using MRI presents a wide range of quantitative MRI techniques to study the morphology and physiology of the whole body, from the brain to musculoskeletal systems. Illustrating the growing importance of quantitative MRI, the book delivers an indispensable reference for readers who would like to explore in vivo MRI techniques to quantify changes in the morphology and physiology of tissues caused by various disease mechanisms. With internationally renowned experts sharing their insight on the latest developments, the book goes beyond conventional MRI contrast mechanisms to include new techniques that measure electromagnetic and mechanical properties of tissues. Each chapter offers comprehensive information on data acquisition, processing, and analysis techniques as well as clinical applications. The text organizes the techniques based on their primary use either in the brain or the body. Some of the techniques, such as diffusion-weighted imaging and diffusion tensor imaging, span several application areas, including brain imaging, cancer imaging, and musculoskeletal imaging. The book also covers up-and-coming quantitative techniques that explore tissue properties other than the presence of protons (or other MRI-observable nuclei) and their interactions with their environment. These novel techniques provide unique information about the electromagnetic and mechanical properties of tissues and introduce new frontiers of study into disease mechanisms.
Book Synopsis Fast Quantitative Magnetic Resonance Imaging by : Guido Buonincontri
Download or read book Fast Quantitative Magnetic Resonance Imaging written by Guido Buonincontri and published by Morgan & Claypool Publishers. This book was released on 2020-02-20 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among medical imaging modalities, magnetic resonance imaging (MRI) stands out for its excellent soft-tissue contrast, anatomical detail, and high sensitivity for disease detection. However, as proven by the continuous and vast effort to develop new MRI techniques, limitations and open challenges remain. The primary source of contrast in MRI images are the various relaxation parameters associated with the nuclear magnetic resonance (NMR) phenomena upon which MRI is based. Although it is possible to quantify these relaxation parameters (qMRI) they are rarely used in the clinic, and radiological interpretation of images is primarily based upon images that are relaxation time weighted. The clinical adoption of qMRI is mainly limited by the long acquisition times required to quantify each relaxation parameter as well as questions around their accuracy and reliability. More specifically, the main limitations of qMRI methods have been the difficulty in dealing with the high inter-parameter correlations and a high sensitivity to MRI system imperfections. Recently, new methods for rapid qMRI have been proposed. The multi-parametric models at the heart of these techniques have the main advantage of accounting for the correlations between the parameters of interest as well as system imperfections. This holistic view on the MR signal makes it possible to regress many individual parameters at once, potentially with a higher accuracy. Novel, accurate techniques promise a fast estimation of relevant MRI quantities, including but not limited to longitudinal (T1) and transverse (T2) relaxation times. Among these emerging methods, MR Fingerprinting (MRF), synthetic MR (syMRI or MAGIC), and T1‒T2 Shuffling are making their way into the clinical world at a very fast pace. However, the main underlying assumptions and algorithms used are sometimes different from those found in the conventional MRI literature, and can be elusive at times. In this book, we take the opportunity to study and describe the main assumptions, theoretical background, and methods that are the basis of these emerging techniques. Quantitative transient state imaging provides an incredible, transformative opportunity for MRI. There is huge potential to further extend the physics, in conjunction with the underlying physiology, toward a better theoretical description of the underlying models, their application, and evaluation to improve the assessment of disease and treatment efficacy.
Book Synopsis Quantitative MRI of the Spinal Cord by : Julien Cohen-Adad
Download or read book Quantitative MRI of the Spinal Cord written by Julien Cohen-Adad and published by Academic Press. This book was released on 2014-01-16 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantitative MRI of the Spinal Cord is the first book focused on quantitative MRI techniques with specific application to the human spinal cord. This work includes coverage of diffusion-weighted imaging, magnetization transfer imaging, relaxometry, functional MRI, and spectroscopy. Although these methods have been successfully used in the brain for the past 20 years, their application in the spinal cord remains problematic due to important acquisition challenges (such as small cross-sectional size, motion, and susceptibility artifacts). To date, there is no consensus on how to apply these techniques; this book reviews and synthesizes state-of-the-art methods so users can successfully apply them to the spinal cord. Quantitative MRI of the Spinal Cord introduces the theory behind each quantitative technique, reviews each theory’s applications in the human spinal cord and describes its pros and cons, and suggests a simple protocol for applying each quantitative technique to the spinal cord. Chapters authored by international experts in the field of MRI of the spinal cord Contains “cooking recipes —examples of imaging parameters for each quantitative technique—designed to aid researchers and clinicians in using them in practice Ideal for clinical settings
Book Synopsis Microstructure with Magnetic Resonance by : Valerij G. Kiselev
Download or read book Microstructure with Magnetic Resonance written by Valerij G. Kiselev and published by Academic Press. This book was released on 2021-11-01 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microstructure with Magnetic Resonance: Problems and Solutions responds to the challenge of how to see the invisible with magnetic resonance imaging. Technically, the goal is to quantify cellular-level properties of biological tissues and microarchitecture of porous media orders of magnitude below the achievable resolution of MR. While the interest in this area has grown exponentially, current research involves physics outside the scope of standard NMR and MRI textbooks. Microstructure with Magnetic Resonance: Problems and Solutions introduces readers to methods of describing complex media in statistical terms, and covers the effects of complex microenvironments on the MR signal phase, on the transverse relaxation, and on different facets of the diffusion-weighted signal. The book presents the material as a set of problems with detailed solutions, that build on each other, stimulating a hands-on approach to learning. Each chapter begins with a short introduction to the topic, followed by problems, solutions, and a summary of key points. The problems start from the basics, and bring the reader step-by-step to the frontier of current knowledge. The overall focus is on gaining physical insight, by drawing on simple physical analogies and dimensional analysis, which help to reproduce the essence of the results obtained in classical and recent studies. The necessary mathematics is collected in dedicated appendices. With this book the reader will: • Understand the classic and current literature on microstructure mapping with NMR and MRI; • Become familiar with the modern trends in microstructure MR; • Be able to design new experiments using MR based on a solid theoretical foundation. • Explains physics necessary to understand how the microscopic structure of biological tissues and porous media manifests itself in different magnetic resonance contrasts (phase, relaxation, diffusion). • Uses a unique problem/solution structure to provide for efficient learning from the basics to the frontiers of knowledge. • Tested through numerous teaching courses for trainees.
Book Synopsis The Challenges of MRI by : Helene Ratiney
Download or read book The Challenges of MRI written by Helene Ratiney and published by John Wiley & Sons. This book was released on 2024-05-21 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: After a review of the essential concepts of magnetic resonance imaging (MRI), The Challenges of MRI presents the recent techniques and methods of MRI and resulting medical applications. These techniques provide access to information that goes well beyond anatomy, with functional, hemodynamic, structural, biomechanical and biochemical information. MRI allows us to probe living organisms in a multitude of ways, guaranteeing the potential for continuous development involving several disciplines: physics, electronics, life sciences, signal processing and medicine. This collective work is made up of chapters written and designed by experts from the French community. They have endeavored to describe the techniques by recalling the underlying physics and detailing the modeling, methods and strategies for acquiring or extracting information. This book is aimed at master’s students and PhD students, as well as lecturers and researchers in medical imaging and radiology.
Book Synopsis Quantitative MRI of the Brain by : Paul Tofts
Download or read book Quantitative MRI of the Brain written by Paul Tofts and published by John Wiley & Sons. This book was released on 2005-08-19 with total page 650 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2004 BMA Medical Book Competition Winner (Radiology category) “This is an exciting book, with a new approach to use of the MRI scanner. It bridges the gap between clinical research and general neuro-radiological practice. It is accessible to the clinical radiologist, and yet thorough in its treatment of the underlying physics and of the science of measurement. It is likely to become a classic.” British Medical Association This indispensable 'how to' manual of quantitative MR is essential for anyone who wants to use the gamut of modern quantitative methods to measure the effects of neurological disease, its progression, and its response to treatment. It contains both the methodology and clinical applications, reflecting the increasing interest in quantitative MR in studying disease and its progression. The editor is an MR scientist with an international reputation for high quality research The contributions are written jointly by MR physicists and MR clinicians, producing a practical book for both the research and medical communities A practical book for both the research and medical communities “Paul Tofts has succeeded brilliantly in capturing the essence of what needs to become the future of radiology in particular, and medicine in general – quantitative measurements of disease.” Robert I. Grossman, M.D. New York, University School of Medicine (from the Foreword)
Book Synopsis Quantitative MRI in Cancer by : Thomas E. Yankeelov
Download or read book Quantitative MRI in Cancer written by Thomas E. Yankeelov and published by Taylor & Francis. This book was released on 2011-09-13 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: Propelling quantitative MRI techniques from bench to bedside, Quantitative MRI in Cancer presents a range of quantitative MRI methods for assessing tumor biology. It includes biophysical and theoretical explanations of the most relevant MRI techniques as well as examples of these techniques in cancer applications.The introductory part of the book c
Book Synopsis Assessing Cellular Microstructure in Biological Tissues using In Vivo Diffusion-Weighted Magnetic Resonance by : Julien Valette
Download or read book Assessing Cellular Microstructure in Biological Tissues using In Vivo Diffusion-Weighted Magnetic Resonance written by Julien Valette and published by Frontiers Media SA. This book was released on 2019-05-16 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques have opened new doors for examining biological tissues in vivo. By combining sensitization to diffusion using magnetic field gradients with a variety of imaging and localization schemes, diffusion-weighted MRI and diffusion-weighted MRS allow investigating translational diffusion of endogenous molecules, such as water or metabolites, in biological tissues, most commonly the brain but also other organs such as the prostate. The typical voxel resolution of MRI or MRS is in the millimeter to centimeter range, much lower than the cellular scale. However, as molecules are typically diffusing over just a few µm during the duration of the measurement (the “diffusion time”) and encounter numerous biological membranes at these scales, the average cellular microstructure has a critical influence on the measured diffusion signal. Hence, diffusion-weighted MRI and diffusion-weighted MRS are sensitive to tissue microstructure at a scale well below the nominal imaging resolution. However, the connection between diffusion properties and tissue microstructure remains indirect, so any attempt to quantify microstructure will rely on modeling. The goal of this Research Topic was to gather experts in various acquisition and modeling strategies and show how these approaches, despite their own strengths and weaknesses, can yield unique information about cellular microstructure, and sometimes complement each other.
Download or read book MRI written by Angshul Majumdar and published by CRC Press. This book was released on 2018-09-03 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of magnetic resonance imaging (MRI) has developed rapidly over the past decade, benefiting greatly from the newly developed framework of compressed sensing and its ability to drastically reduce MRI scan times. MRI: Physics, Image Reconstruction, and Analysis presents the latest research in MRI technology, emphasizing compressed sensing-based image reconstruction techniques. The book begins with a succinct introduction to the principles of MRI and then: Discusses the technology and applications of T1rho MRI Details the recovery of highly sampled functional MRIs Explains sparsity-based techniques for quantitative MRIs Describes multi-coil parallel MRI reconstruction techniques Examines off-line techniques in dynamic MRI reconstruction Explores advances in brain connectivity analysis using diffusion and functional MRIs Featuring chapters authored by field experts, MRI: Physics, Image Reconstruction, and Analysis delivers an authoritative and cutting-edge treatment of MRI reconstruction techniques. The book provides engineers, physicists, and graduate students with a comprehensive look at the state of the art of MRI.
Book Synopsis Advanced Quantitative Imaging of Musculoskeletal Disorders by : Rajeev Chaudhary
Download or read book Advanced Quantitative Imaging of Musculoskeletal Disorders written by Rajeev Chaudhary and published by . This book was released on 2016 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Imaging of tissues requires knowledge of size-scales across the depth of focus. There are several limitations in terms of resolution, signal-to-noise ratio, physical size constraints, and penetration depth. All of these need to be taken into consideration before attempting an experiment on a patient, animal, or phantom. This thesis describes the different ways to characterize musculoskeletal tissue microstructure using non-invasive methods of quantitative Magnetic Resonance Imaging (MRI) on the macroscale to more microscale methods of Second Harmonic Generation (SHG) imaging microscopy and the classical bright field methodologies used in histology and immunohistochemistry. Chapter 1 of this thesis describes the basic science of the periosteum and hyaline articular cartilage, as well as explains the different quantitative MRI and SHG techniques used clinically and in research for osteoarthritis (OA) and limb length discrepancies. In Chapter 2, the first research MRI technique, Quantitative Magnetization Transfer (QMT), illuminates the ability of using off-resonance MT pulses to resolve the cartilage macromolecular pool of protons, typically invisible in traditional MRI. Chapter 3 focuses on another powerful MRI technique, Multicomponent Driven Equilibrium Singe Pulse Observation of T1 & T2 (mcDESPOT), which decomposes the free and macromolecular cartilage water pools typically averaged in a voxel, and the mcDESPOT parameters are compared at multiple angles to the main magnetic field to determine sensitivity due to the Magic Angle Effect. Chapter 4 shifts gears to a more microscopic perspective, using SHG and bulk optical scattering to assess the different cartilage histological zones. Chapter 5 focuses on different surgical techniques, less invasive than the traditional invasive osteotomy, using a rabbit animal model aimed elucidate the accelerated bone growth for pediatric patients with limb length discrepancies. Chapters 6 and 7 attempt to further elucidate the bone growth mechanism, by focusing on SHG of periosteal strips and on the bone at different anatomical regions of interest, respectively. Lastly, Chapter 8 provides details for future work of these projects. In summary, this thesis describes quantitative imaging techniques across different size-scales of two important musculoskeletal disorders, and the knowledge of how microstructural changes reflect changes on the macroscale can provide powerful, non-invasive biomarkers for disease.
Book Synopsis In Vivo Quantification of Cardiac Microstructure with Convex Optimized Diffusion Weighted MRI by : Eric Aliotta
Download or read book In Vivo Quantification of Cardiac Microstructure with Convex Optimized Diffusion Weighted MRI written by Eric Aliotta and published by . This book was released on 2017 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diffusion weighted imaging (DWI) is a powerful quantitative magnetic resonance imaging (MRI) technique that can probe tissues in vivo at the microscopic level and provide insight into cellular microstructural environment. Cardiac DWI has great potential value in its ability to answer open questions regarding myocardial structure, dynamics, and remodeling. Unfortunately, several technical limitations of current DWI techniques make its application in the beating heart very challenging, which leads to erroneous or inconsistent results. Amongst the challenges are an extreme sensitivity to bulk physiological motion, low signal to noise ratios (SNR), long scan times, and geometric image distortions. In this dissertation, these limitations are addressed with novel technical developments applied to the DWI pulse sequence including convex optimized diffusion gradient waveform design and multi-parametric tissue characterization. A brief introduction to Nuclear Magnetic Resonance (NMR) and MRI is provided in Chapter 1. This leads into a description of the fundamental components of a DWI acquisition in Chapter 2 and an overview of the current state of cardiac DWI in Chapter 3. In Chapter 4, a novel DWI strategy called Convex Optimized Diffusion Encoding (CODE) is described. CODE is a mathematical framework that formulates diffusion encoding gradient design as a convex optimization problem and automatically generates motion compensated (MOCO) waveforms that achieve the shortest possible echo times (TE) and thus improve SNR. First and second order moment nulled CODE (CODE-M1M2) permits DWI that is robust to cardiac motion with higher SNR than an existing MOCO technique. First order motion compensated CODE-M1 also improves robustness to cardiac induced motion in liver DWI with higher SNR than M1 nulled bipolar DWI. CODE can also be used for non-motion compensated DWI and improves SNR compared with traditional monopolar DWI in the brain. In Chapter 5 we present a multi-parametric DWI strategy that simultaneously yields maps of the apparent diffusion coefficient (ADC) and T2 relaxation time constant in the heart (T2+ADC). Typically, DWI protocols include multiple acquisitions with a range of diffusion encoding strengths (b-value), but with constant TE to isolate the effect of diffusion of the signal. The joint T2+ADC approach varies both b-value and TE within the acquisition to facilitate estimation of both ADC and T2 relaxation. T2+ADC permits joint reconstruction with no increase in scan time compared with DWI alone and no effect on ADC measurement. In Chapter 6 we use CODE-M1M2 diffusion encoding to perform cardiac diffusion tensor imaging (cDTI) and generate maps of myocardial microstructure in healthy volunteers. cDTI can be used to map myocardial fiber and myolaminar sheetlet orientations, which can contribute to our understanding of ventricular microstructure in health and disease and facilitate sophisticated mechanical models of cardiac dynamics. However, it is important to understand the uncertainty underlying these measurements to inform interpretation and define acquisition limitations. We apply a previously described bootstrap technique to measure the uncertainty in the diffusion tensors derived from CODE-M1M2 cDTI and establish achievable levels of precision in clinically feasible scan times. In Chapter 7 the CODE framework is extended to compensate for the effect of eddy currents, which are a common cause of image distortions in DWI and DTI. Diffusion encoding gradients must be very strong to encode microscopic molecular displacements and these strong gradient pulses induce unwanted eddy currents in conductive MRI hardware components. If not addressed, eddy currents lead to distorted images and corrupted diffusion parameter estimates. We incorporate an eddy current model into the CODE optimization framework to develop eddy current nulled CODE (EN-CODE). EN-CODE accomplishes eddy current nulling with TEs that are comparable to traditional monopolar encoding and much shorter than the established twice refocused spin echo (TRSE) technique for eddy current nulling. The developments described in this dissertation represent an improvement in the flexibility, efficiency, and robustness of diffusion encoding. The CODE framework can also be easily modified to address additional constraints and thus may prove useful in currently unforeseen applications.
Book Synopsis Multiparametric Quantitative MRI of the Cervical Spinal Cord to Measure Microstructure and Tissue Injury by : Allan Russell Martin
Download or read book Multiparametric Quantitative MRI of the Cervical Spinal Cord to Measure Microstructure and Tissue Injury written by Allan Russell Martin and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An array of spinal cord (SC) quantitative MRI (qMRI) techniques can measure aspects of microstructure and tissue injury. This research develops a clinically feasible multiparametric MRI protocol, including diffusion tensor imaging (DTI) fractional anisotropy (FA), magnetization transfer ratio (MTR), and measurement of SC cross-sectional area (CSA). A novel biomarker of white matter (WM) injury is also introduced, normalizing T2*WI WM signal intensity by grey matter (T2*WI WM/GM). A study of 40 healthy subjects establishes methods, normalization procedures, normative values, and reliability. 58 patients with degenerative cervical myelopathy (DCM) are studied, showing significant differences in 10 metrics. Combining these measures using multivariate methods overcomes the limitations of each technique, achieving good diagnostic accuracy and clinical correlation. T2*WI WM/GM shows strong potential as a novel biomarker, comparing favourably with established biomarkers FA and MTR. Our study of healthy subjects identifies an alarming rate of asymptomatic SC compression (ASCC) at 50%. Objective criteria and automated shape analysis are developed to create a new definition of SC compression, and qMRI demonstrates significant tissue injury in this group. This finding suggests the potential for pre-symptomatic diagnosis of DCM and other spinal pathologies. Finally, a longitudinal study compares multiparametric qMRI with clinical measures for monitoring disease progression in DCM, indicating that modified Japanese Orthopedic Association (mJOA) score is insensitive to detect progression, whereas qMRI showed tissue progression more often than comprehensive clinical assessments. These results suggest that natural history studies employing mJOA underestimate progression, due to neuroplasticity and behavioural adaptation. Combined qMRI and clinical data are now being used to inform surgical decision-making for individual patients. Reliable multiparametric assessment of SC microstructure is possible using clinically suitable methods. This approach shows strong clinical utility for individual patients, including good diagnostic accuracy, correlations with impairment, detection of tissue injury in asymptomatic individuals, and detection of progressive tissue injury in DCM patients.
