Download or read book Radiofrequency Pulses for Improved Simultaneous Multislice Magnetic Resonance Imaging written by Anuj Sharma and published by . This book was released on 2015 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improved Magnetic Resonance Imaging Using Frequency swept Radiofrequency Pulses written by Jang-Yeon Park and published by . This book was released on 2006 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improvements in Magnetic Resonance Imaging Excitation Pulse Design written by Adam Charles Zelinski and published by . This book was released on 2008 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on the design of magnetic resonance imaging (MRI) radio-frequency (RF) excitation pulses, and its primary contributions are made through connections with the novel multiple-system single-output (MSSO) simultaneous sparse approximation problem. The contributions are both conceptual and algorithmic and are validated with simulations, as well as anthropogenic-object-based and in vivo trials on MRI scanners. Excitation pulses are essential to MRI: they excite nuclear spins within a subject that are detected by a resonant coil and then reconstructed into images. Pulses need to be as short as possible due to spin relaxation, tissue heating, and main field inhomogeneity limitations. When magnetic spins are tilted by only a small amount, pulse transmission may be interpreted as depositing energy in a continuous three-dimensional Fourier-like domain along a one-dimensional contour to form an excitation in the spatial domain. Pulse duration is proportional to the length of the contour and inversely proportional to the rate at which it is traversed, and the rate is limited by system gradient hardware restrictions. Joint design of the contour and a corresponding excitation pulse is a difficult and central problem, while determining near-optimal energy deposition once the contour is fixed is significantly easier. We first pose the NP-Hard MSSO problem and formulate greedy and convex relaxation-based algorithms with which to approximately solve it. We find that second-order-cone programming and iteratively-reweighted least squares approaches are practical techniques for solving the relaxed problem and prove that single-vector sparse approximation of a complex-valued vector is an MSSO problem.

Download or read book Trajectory Optimization and Machine Learning Radiofrequency Pulses for Enhanced Magnetic Resonance Imaging written by Julianna Denise Ianni and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rf Pulse Design for Parallel Excitation in Magnetic Resonance Imaging written by Yinan Liu and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Parallel excitation is an emerging technique to improve or accelerate multi-dimensional spatially selective excitations in magnetic resonance imaging (MRI) using multi-channel transmit arrays. The technique has potential in many applications, such as accelerating imaging speed, mitigating field inhomogeneity in high-field MRI, and alleviating the susceptibility artifact in functional MRI (fMRI). In these applications, controlling radiofrequency (RF) power deposition (quantified by Specific Absorption Rate, or SAR) under safe limit is a critical issue, particularly in high-field MRI. This \dissertation will start with a review of multidimensional spatially selective excitation in MRI and current parallel excitation techniques. Then it will present two new RF pulse design methods to achieve reduced local/global SAR for parallel excitation while preserving the time duration and excitation pattern quality. Simulations incorporating human-model based tissue density and dielectric property were performed. Results have show that the proposed methods can achieve significant SAR reductions without enlonging the pulse duration at high-fields.

Download or read book Radio Frequency Pulse Designs for Magnetic Resonance Imaging at High Field written by Jason E. Moore and published by . This book was released on 2011 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design of Multidimensional Radiofrequency Pulses in Magnetic Resonance Imaging written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Non selective Refocusing Pulse Design in Parallel Transmission for Magnetic Resonance Imaging of the Human Brain at Ultra High Field written by Aurélien Massire and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Magnetic Resonance Imaging (MRI), the increase of the static magnetic field strength is used to provide in theory a higher signal-to-noise ratio, thereby improving the overall image quality. The purpose of ultra-high-field MRI is to achieve a spatial image resolution sufficiently high to be able to distinguish structures so fine that they are currently impossible to view in a non-invasive manner. However, at such static magnetic fields strengths, the wavelength of the electromagnetic waves sent to flip the water proton spins is of the same order of magnitude than the scanned object. Interference wave phenomena are then observed, which are caused by the radiofrequency (RF) field inhomogeneity within the object. These generate signal and/or contrast artifacts in MR images, making their exploitation difficult, if not impossible, in certain areas of the body. It is therefore crucial to provide solutions to mitigate the non-uniformity of the spins excitation. Failing this, these imaging systems with very high fields will not reach their full potential.For relevant high field clinical diagnosis, it is therefore necessary to create RF pulses homogenizing the excitation of all spins (here of the human brain), and optimized for each individual to be imaged. For this, an 8-channel parallel transmission system (pTX) was installed in our 7 Tesla scanner. While most clinical MRI systems only use a single transmission channel, the pTX extension allows to simultaneously playing various forms of RF pulses on all channels. The resulting sum of the interference must be optimized in order to reduce the non-uniformity typically seen.The objective of this thesis is to synthesize this type of tailored RF pulses, using parallel transmission. These pulses will have as an additional constraint the compliance with the international exposure limits for radiofrequency exposure, which induces a temperature rise in the tissue. In this sense, many electromagnetic and temperature simulations were carried out as an introduction of this thesis, in order to assess the relationship between the recommended RF exposure limits and the temperature rise actually predicted in tissues.This thesis focuses specifically on the design of all RF refocusing pulses used in non-selective MRI sequences based on the spin-echo. Initially, only one RF pulse was generated for a simple application: the reversal of spin dephasing in the transverse plane, as part of a classic spin echo sequence. In a second time, sequences with very long refocusing echo train applied to in vivo imaging are considered. In all cases, the mathematical operator acting on the magnetization, and not its final state as is done conventionally, is optimized. The gain in high field imaging is clearly visible, as the necessary mathematical operations (that is to say, the rotation of the spins) are performed with a much greater fidelity than with the methods of the state of the art. For this, the generation of RF pulses is combining a k-space-based spin excitation method, the kT-points, and an optimization algorithm, called Gradient Ascent Pulse Engineering (GRAPE), using optimal control.This design is relatively fast thanks to analytical calculations rather than finite difference methods. The inclusion of a large number of parameters requires the use of GPUs (Graphics Processing Units) to achieve computation times compatible with clinical examinations. This method of designing RF pulses has been experimentally validated successfully on the NeuroSpin 7 Tesla scanner, with a cohort of healthy volunteers. An imaging protocol was developed to assess the image quality improvement using these RF pulses compared to typically used non-optimized RF pulses. All methodological developments made during this thesis have contributed to improve the performance of ultra-high-field MRI in NeuroSpin, while increasing the number of MRI sequences compatible with parallel transmission.

Download or read book New Approaches to Simultaneous Multislice Magnetic Resonance Imaging written by Klaus Eickel and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Resonance Imaging, MRI, Deep Learning, Image Reconstruction, Perfusion Imaging, Tracer Kinetics, Pharmacokinetics, Simultaneous Multi-Slice Imaging, SMS, Parallel Imaging, Medical Physics, Medical Imaging.

Download or read book Cardiovascular MR Manual written by Sven Plein and published by Springer. This book was released on 2015-09-15 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides an introduction to CMR imaging that is understandable and focused on the relevant information needed to using CMR imaging in clinical practice. Cardiovascular magnetic resonance (CMR) imaging has become an established imaging modality with an expanding range of clinical indications. While in the past the availability of CMR imaging was limited to a few specialist centres the method is becoming more widely available. Most clinicians therefore need to have a general understanding of the diagnostic information that can be obtained from CMR imaging, the indications for referral as well as contraindications and limitations of the method. For cardiologists and radiologists in particular, CMR imaging will become a routine diagnostic tool and training curricula in Cardiology or Radiology reflect this trend by increasingly demanding training in CMR imaging.

Download or read book Parallel Imaging in Clinical MR Applications written by Stefan O. Schönberg and published by Springer Science & Business Media. This book was released on 2007-01-11 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the first in-depth introduction to parallel imaging techniques and, in particular, to the application of parallel imaging in clinical MRI. It will provide readers with a broader understanding of the fundamental principles of parallel imaging and of the advantages and disadvantages of specific MR protocols in clinical applications in all parts of the body at 1.5 and 3 Tesla.

Download or read book Mathematics and Physics of Emerging Biomedical Imaging written by Committee on the Mathematics and Physics of Emerging Dynamic Biomedical Imaging and published by National Academies Press. This book was released on 1996-03-13 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt: This cross-disciplinary book documents the key research challenges in the mathematical sciences and physics that could enable the economical development of novel biomedical imaging devices. It is hoped that the infusion of new insights from mathematical scientists and physicists will accelerate progress in imaging. Incorporating input from dozens of biomedical researchers who described what they perceived as key open problems of imaging that are amenable to attack by mathematical scientists and physicists, this book introduces the frontiers of biomedical imaging, especially the imaging of dynamic physiological functions, to the educated nonspecialist. Ten imaging modalities are covered, from the well-established (e.g., CAT scanning, MRI) to the more speculative (e.g., electrical and magnetic source imaging). For each modality, mathematics and physics research challenges are identified and a short list of suggested reading offered. Two additional chapters offer visions of the next generation of surgical and interventional techniques and of image processing. A final chapter provides an overview of mathematical issues that cut across the various modalities.

Download or read book Improved Magnetic Resonance Temperature Imaging Through Pulse Sequence and Reconstruction Techniques written by Nicholas Todd and published by . This book was released on 2010 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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

Download or read book Introduction to Functional Magnetic Resonance Imaging written by Richard B. Buxton and published by Cambridge University Press. This book was released on 2009-08-27 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: Functional Magnetic Resonance Imaging (fMRI) has become a standard tool for mapping the working brain's activation patterns, both in health and in disease. It is an interdisciplinary field and crosses the borders of neuroscience, psychology, psychiatry, radiology, mathematics, physics and engineering. Developments in techniques, procedures and our understanding of this field are expanding rapidly. In this second edition of Introduction to Functional Magnetic Resonance Imaging, Richard Buxton – a leading authority on fMRI – provides an invaluable guide to how fMRI works, from introducing the basic ideas and principles to the underlying physics and physiology. He covers the relationship between fMRI and other imaging techniques and includes a guide to the statistical analysis of fMRI data. This book will be useful both to the experienced radiographer, and the clinician or researcher with no previous knowledge of the technology.

Download or read book Advanced Neuro MR Techniques and Applications written by In-Young Choi and published by Academic Press. This book was released on 2021-11-17 with total page 640 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Neuro MR Techniques and Applications gives detailed knowledge of emerging neuro MR techniques and their specific clinical and neuroscience applications, showing their pros and cons over conventional and currently available advanced techniques. The book identifies the best available data acquisition, processing, reconstruction and analysis strategies and methods that can be utilized in clinical and neuroscience research. It is an ideal reference for MR scientists and engineers who develop MR technologies and/or support clinical and neuroscience research and for high-end users who utilize neuro MR techniques in their research, including clinicians, neuroscientists and psychologists. Trainees such as postdoctoral fellows, PhD and MD/PhD students, residents and fellows using or considering the use of neuro MR technologies will also be interested in this book. Presents a complete reference on advanced Neuro MR Techniques and Applications Edited and written by leading researchers in the field Suitable for a broad audience of MR scientists and engineers who develop MR technologies, as well as clinicians, neuroscientists and psychologists who utilize neuro MR techniques in their research

Download or read book MR and CT Perfusion and Pharmacokinetic Imaging Clinical Applications and Theoretical Principles written by Roland Bammer and published by Lippincott Williams & Wilkins. This book was released on 2016-03-03 with total page 2558 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.