Download or read book Portable Low Field MRI Scanners written by David J. Ariando and published by Springer Nature. This book was released on with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Design and Fabrication of Portable MRI Systems written by Patrick Christopher McDaniel and published by . This book was released on 2020 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, I have developed techniques for designing portable MRI scanners and have applied them to three portable systems for brain imaging. I first describe the procedue for designing a portable, low-field MRI scanner - in particular, how the constraints of compactness and portability affect the design of all system components (magnets, coils, sequences, RF pulses, and reconstruction schemes). I then describe the design of the principal hardware components of a portable MRI system: the B0 magnet, the magnet shim array, the gradient coils, and the RF coils. This work makes novel use of numerical and computational tools for both sub-system design and physical construction. I next apply this paradigm to the design of gradient coils and a shim magnet array for portable whole-brain MRI scanner and demonstrate in vivo adult brain images. Finally, I describe two novel MRI scanners designed ab ovo using the approach described herein. The former is the "MR Cap", a single-sided MRI device designed for imaging over a reduced 8 × 8 × 3cm3 region of the adult brain; the latter is the "Helmet MRI", a whole-brain scanner optimized specifically for the head geometry.
Download or read book Clinical Low Field Strength Magnetic Resonance Imaging written by Hans-Martin Klein and published by Springer. This book was released on 2015-10-03 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers all aspects of low field MRI, describing its advantages, problems and prerequisites. Individual chapters are devoted to site planning, safety considerations, coils, imaging technique, image quality optimization, the imaging of different anatomic regions and likely future developments. The factors that must be borne in mind when selecting a low field system are clearly identified and detailed attention is paid to the applications for which such a system is adequate. The focus on high field systems has led to a situation where only a few systems with field strengths lower than 0.5 T survive. Some of these systems possess high field features such as multichannel coils and strong gradients; furthermore, sequence technology and image processing techniques taken from higher field strength systems have resulted in impressive imaging capabilities. While 1.5-T systems will probably continue to remain the standard, low field systems offer advantages such as the feasibility of dynamic joint examinations, improvement of T1 contrast, reduction of “missile effects” and decreased radiofrequency exposure. Low field strength MRI consequently has the potential to contribute to optimal patient management and given comparable image quality, its application may become an issue of patient safety. This book will be an invaluable asset to all who are involved in planning and/or running a low field strength MRI facility.
Download or read book Demonstration of Anatomical Imaging with a Portable Non cryogenic Ultra low field MRI System written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Portable MRI Developed at Los Alamos written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Scientists at Los Alamos National Laboratory are developing an ultra-low-field Magnetic Resonance Imaging (MRI) system that could be low-power and lightweight enough for forward deployment on the battlefield and to field hospitals in the World's poorest regions. "MRI technology is a powerful medical diagnostic tool," said Michelle Espy, the Battlefield MRI (bMRI) project leader, "ideally suited for imaging soft-tissue injury, particularly to the brain." But hospital-based MRI devices are big and expensive, and require considerable infrastructure, such as large quantities of cryogens like liquid nitrogen and helium, and they typically use a large amount of energy. "Standard MRI machines just can't go everywhere," said Espy. "Soldiers wounded in battle usually have to be flown to a large hospital and people in emerging nations just don't have access to MRI at all. We've been in contact with doctors who routinely work in the Third World and report that MRI would be extremely valuable in treating pediatric encephalopathy, and other serious diseases in children." So the Los Alamos team started thinking about a way to make an MRI device that could be relatively easy to transport, set up, and use in an unconventional setting. Conventional MRI machines use very large magnetic fields that align the protons in water molecules to then create magnetic resonance signals, which are detected by the machine and turned into images. The large magnetic fields create exceptionally detailed images, but they are difficult and expensive to make. Espy and her team wanted to see if images of sufficient quality could be made with ultra-low-magnetic fields, similar in strength to the Earth's magnetic field. To achieve images at such low fields they use exquisitely sensitive detectors called Superconducting Quantum Interference Devices, or SQUIDs. SQUIDs are among the most sensitive magnetic field detectors available, so interference with the signal is the primary stumbling block. "SQUIDs are so sensitive they'll respond to a truck driving by outside or a radio signal 50 miles away," said Al Urbaitis, a bMRI engineer. The team's first generation bMRI had to be built in a large metal housing in order to shield it from interference. Now the Los Alamos team is working in the open environment without the large metal housing using a lightweight series of wire coils that surround the bMRI system to compensate the Earth's magnetic field. In the future, the field compensation system will also function similar to noise-cancelling headphones to eradicate invading magnetic field signals on-the-fly.
Download or read book Radiology in Global Health written by Daniel J. Mollura and published by Springer. This book was released on 2014-07-02 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: The World Health Organization stated that approximately two-thirds of the world’s population lacks adequate access to medical imaging. The scarcity of imaging services in developing regions contributes to a widening disparity of health care and limits global public health programs that require imaging. Radiology is an important component of many global health programs, including those that address tuberculosis, AIDS-related disease, trauma, occupational and environmental exposures, breast cancer screening, and maternal-infant health care. There is a growing need for medical imaging in global health efforts and humanitarian outreach, particularly as an increasing number of academic, government, and non-governmental organizations expand delivery of health care to disadvantaged people worldwide. To systematically deploy clinical imaging services to low-resource settings requires contributions from a variety of disciplines such as clinical radiology, epidemiology, public health, finance, radiation physics, information technology, engineering, and others. This book will review critical concepts for those interested in managing, establishing, or participating in a medical imaging program for resource-limited environments and diverse cross-cultural contexts undergoing imaging technology adaptation.
Download or read book Advances in Portable TRASE MRI written by Aaron R. Purchase and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance imaging (MRI) is a valuable medical diagnostic technique due to its exceptional soft tissue contrast. Unfortunately, standard clinical MRI systems have limited accessibility worldwide, especially in developing countries, due to high costs, high weight, large physical dimensions, and maintenance and operating complexity. Standard MRI systems are currently inaccessible to over half the world's population. In MRI accessible regions, they are the bottlenecks of the clinical workflow due to high patient volume and low scanner numbers. Portable, low-cost, and clinically relevant MRI systems have many applications worldwide, such as alleviating accessibility issues in developing countries, rural areas, emergency rooms and medical clinics for point-of-care diagnostic imaging. In addition, mobile MRI systems may find application in ground and air ambulance services, in the military, and even beyond Earth on long-duration spaceflight. Standard MRI systems use gradients of the main magnetic field for spatial encoding, requiring expensive and bulky hardware. A novel MRI encoding method, called Transmit Array Spatial Encoding (TRASE), uses the phase of the radiofrequency (RF) field for spatial encoding signal rather than applying a switching B0 gradient. TRASE removes the need for the entire standard B0 gradient system and relaxes the main magnet's homogeneity requirement, leading to compact, lower cost, and portable MRI systems. However, the first in vivo TRASE MR wrist images, obtained in 2013, were acquired using an immobile 0.2 T magnet and with low spatial resolution due to RF hardware limitations. The objectives of this research were to (a) design and construct a new RF amplifier to improve TRASE spatial resolution; (b) design and construct a new portable magnet for TRASE to reduce the overall weight, size and cost of the system; (c) investigate magnetic field modifications allowing in vivo TRASE imaging on the constructed portable magnet; and (d) design and construct an accurate magnet rotation system that would simplify the 2D TRASE MRI hardware and acquisition technique. An RF power amplifier is an essential component in all MRI systems. Unfortunately, no commercial amplifier exists to fulfil the needs of the TRASE MRI technique, requiring a high duty cycle, high RF output power and independently controlled multi-channel capability. Therefore, we designed and constructed an RF power amplifier and tested it on the bench. In addition, the amplifier performance was tested using a 0.22 T MRI magnet with a twisted solenoid and saddle RF coil combination capable of single-axis TRASE. We showed that the amplifier is capable of sequential, dual-channel operation up to 50% duty cycle, 1 kW peak output per channel and highly stable 100 us RF pulse trains. Furthermore, high spatial resolution one-dimensional TRASE was obtained with the power amplifier to demonstrate its capability. Although TRASE resolution was improved with the new RF amplifier, the main magnet prevents portability and has high associated costs. Recently designed Halbach magnets, made of permanent magnet blocks distributed around a cylinder, used for portable MRI systems are much lighter and more compact than standard biplanar permanent or superconductive magnets. However, improved designs and manufacturing techniques aiming at a lower weight and smaller external size are of continuing interest, especially for space flight applications. In this work, we designed and constructed a 67 mT Halbach magnet with a very low aspect-ratio (length per inner diameter ~ 1:1) that produces almost identical homogeneity (11,152 ppm) as simulations (11,451 ppm) within a 12.7 cm diameter, 1 cm long cylinder region of interest (ROI). The magnet support structure was 3D printed ring-by-ring and assembled coaxially. The final magnet weight is only 25 kilograms and may be disassembled for transportation. Although the constructed Halbach magnet is compact and portable, the remaining field inhomogeneity is not well suited to slice selection using the twisted-solenoid TRASE RF coils. Therefore, the bare Halbach magnet's field requires adjustments for in-vivo TRASE MRI. As a first approach to field adjustments, a simulation study was completed to determine the feasibility and performance of various permanent magnet block configurations used as a shim array to achieve a desired target field in the ROI. Although the presented shim arrays would be inexpensive and straightforward to manufacture, excitation volumes are always present outside the ROI, requiring further field optimization or development of a new receive system to allow in-vivo TRASE. Despite the magnet's field inhomogeneity, magnet rotation allows a 2D TRASE image acquisition using two RF transmit coils rather than three, significantly reducing challenges with RF coil decoupling and reducing costs due to one less required RF amplifier channel. Accurate and high-resolution angular rotation of the Halbach magnet was achieved using an inexpensive stepper motor and driver. The proof-of-concept was verified by obtaining a set of 1D TRASE projections and using this data in a 2D TRASE reconstruction technique.
Download or read book Portable MRI written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This project proposes to: (1) provide the power of MRI to situations where it presently isn't available; (2) perform the engineering required to move from lab to a functional prototype; and (3) leverage significant existing infrastructure and capability in ultra-low field MRI. The reasons for doing this: (1) MRI is the most powerful tool for imaging soft-tissue (e.g. brain); (2) Billions don't have access due to cost or safety issues; (3) metal will heat/move in high magnetic fields; (4) Millions of cases of traumatic brain injury in US alone; (5) even more of non-traumatic brain injury; (6) (e.g. stroke, infection, chemical exposure); (7) Need for early diagnostic; (8) 'Signature' wound of recent conflicts; (9) 22% of injuries; (10) Implications for post-traumatic stress disorder; and (11) chronic traumatic encephalopathy.
Download or read book Electromagnetics in Magnetic Resonance Imaging written by Christopher M. Collins and published by Morgan & Claypool Publishers. This book was released on 2016-03-01 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Ultra Low Field Nuclear Magnetic Resonance written by Robert Kraus Jr. and published by Oxford University Press. This book was released on 2014-02-26 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Intraoperative Imaging written by M. Necmettin Pamir and published by Springer Science & Business Media. This book was released on 2010-10-20 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intraoperative imaging technologies have taken an ever-increasing role in the daily practice of neurosurgeons and the increasing attention and interest necessitated international interaction and collaboration. The Intraoperative Imaging Society was formed in 2007. This book brings together highlights from the second meeting of the Intraoperative Imaging Society, which took place in Istanbul-Turkey from June 14 to 17, 2009. Included within the contents of the book is an overview of the emergence and development of the intraoperative imaging technology as well as a glimpse on where the technology is heading. This is followed by in detail coverage of intraoperative MRI technology and sections on intraoperative CT and ultrasonography. There are also sections on multimodality integration, intraoperative robotics and other intraoperative technologies. We believe that this book will provide an up-to date and comprehensive general overview of the current intraoperative imaging technology as well as detailed discussions on individual techniques and clinical results.
Download or read book Equine MRI written by Rachel C. Murray and published by John Wiley & Sons. This book was released on 2010-11-18 with total page 746 pages. Available in PDF, EPUB and Kindle. Book excerpt: Equine MRI is a unique, comprehensive guide to MRI in the horse. Edited by Rachel Murray, a leading authority and researcher in the field with over ten years of equine clinical MRI experience, the book also includes contributions from worldwide experts in the subject. Divided into the following four sections, the book presents key information based on previous validation work and clinical practice: Principles of MRI, including the practicalities of image acquisition and interpretation Normal MRI anatomy and normal variations Different types of pathological change Options for clinical management and prognosis for different conditions MRI is a rapidly expanding area in veterinary medicine that confers detailed, three-dimensional information on both bone and soft tissue. Expanding clinical knowledge, improvements in technology, and practical application of MRI to the standing and recumbent horse means this useful imaging modality has become an integral and essential part of the diagnostic evaluation in lameness and is a realistic option for investigation of ophthalmological, neurological and cranial pathology. Equine MRI enables readers to understand the best ways to achieve good quality images, and provides a detailed explanation of the problems that may occur. With close to 950 normal and abnormal images, this book offers considerable detail and examples of both common and uncommon problems, making it a great reference for equine veterinarians, veterinary students, specialists in equine surgery, and specialists in veterinary imaging.
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 Portable Low cost Magnetic Resonance Imaging written by Clarissa Zimmerman Cooley and published by . This book was released on 2014 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: Purpose: As the premiere modality for brain imaging, MRI could find wider applicability if lightweight, portable systems were available for siting in unconventional locations such as intensive care units (ICUs), physician offices, surgical suites, ambulances, emergency rooms, sports facilities, or rural healthcare sites. Methods: A truly portable (
Download or read book Single Sided NMR written by Federico Casanova and published by Springer Science & Business Media. This book was released on 2011-01-28 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the design of the first functioning single-sided tomograph, the related measurement methods, and a number of applications in medicine, materials science, and chemical engineering. It will be the first comprehensive account of this new device and its applications. Among the key advances of this method is that images can be obtained in much shorter times than originally anticipated, and that even vector maps of flow fields can be measured although the magnetic fields are highly inhomogeneous. Furthermore, the equipment is small, mobile and affordable to small and medium enterprises and can be located in doctors’ offices.
Download or read book Compact NMR written by Bernhard Blümich and published by Walter de Gruyter GmbH & Co KG. This book was released on 2014-08-22 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this book is to provide an introduction to the practical use of mobile NMR at a level as basic as the operation of a smart phone. Each description follows the same didactic pattern: introduction, basic theory, pulse sequences and parameters, beginners-level measurements, advanced-level measurements, and data processing. Nuclear Magnetic Resonance (NMR) spectroscopy is the most popular method for chemists to analyze molecular structures while Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool for medical doctors that provides high-contrast images of biological tissue depicting the brain function and the beating heart. In both applications large super-conducting magnets are employed which magnetize atomic nuclei of an object positioned inside the magnet. Their circulating motion is interrogated by radio-frequency waves. Depending on the operating mode, the frequency spectrum provides the chemist with molecular information, the medical doctor with anatomic images, while the materials scientist is interested in NMR relaxation parameters, which scale with material properties and determine the contrast in magnetic resonance images. Recent advances in magnet technology led to a variety of small permanent magnets, by which NMR spectra, images, and relaxation parameters can be measured with mobile and low-cost instruments.
Download or read book Deblurring Images written by Per Christian Hansen and published by SIAM. This book was released on 2006-01-01 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes the deblurring algorithms and techniques collectively known as spectral filtering methods, in which the singular value decomposition, or a similar decomposition with spectral properties, is used to introduce the necessary regularization or filtering in the reconstructed image. The concise MATLAB® implementations described in the book provide a template of techniques that can be used to restore blurred images from many applications.
