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Novel Mri Technologies For Structural And Functional Imaging Of Tissues With Ultra Short T2 Values
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Book Synopsis Novel MRI Technologies for Structural and Functional Imaging of Tissues with Ultra-short T₂ Values by : Oezen, Ali Caglar
Download or read book Novel MRI Technologies for Structural and Functional Imaging of Tissues with Ultra-short T₂ Values written by Oezen, Ali Caglar and published by KIT Scientific Publishing. This book was released on 2017-06-30 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional MRI has several limitations such as long scan durations, motion artifacts, very loud acoustic noise, signal loss due to short relaxation times, and RF induced heating of electrically conducting objects. The goals of this work are to evaluate and improve the state-of-the-art methods for MRI of tissue with short T?, to prove the feasibility of in vivo Concurrent Excitation and Acquisition, and to introduce simultaneous electroglottography measurement during functional lung MRI.
Book Synopsis Novel MRI Technologies for Structural and Functional Imaging of Tissues with Ultra-short T2 Values by : Ali Caglar Özen
Download or read book Novel MRI Technologies for Structural and Functional Imaging of Tissues with Ultra-short T2 Values written by Ali Caglar Özen and published by . This book was released on 2020-10-09 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional MRI has several limitations such as long scan durations, motion artifacts, very loud acoustic noise, signal loss due to short relaxation times, and RF induced heating of electrically conducting objects. The goals of this work are to evaluate and improve the state-of-the-art methods for MRI of tissue with short T?, to prove the feasibility of in vivo Concurrent Excitation and Acquisition, and to introduce simultaneous electroglottography measurement during functional lung MRI. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.
Book Synopsis New Perspectives on Virtual and Augmented Reality by : Linda Daniela
Download or read book New Perspectives on Virtual and Augmented Reality written by Linda Daniela and published by Routledge. This book was released on 2020-05-31 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: New Perspectives on Virtual and Augmented Reality discusses the possibilities of using virtual and augmented reality in the role of innovative pedagogy, where there is an urgent need to find ways to teach and support learning in a transformed learning environment. Technology creates opportunities to learn differently and presents challenges for education. Virtual reality solutions can be exciting, create interest in learning, make learning more accessible and make learning faster. This book analyses the capabilities of virtual, augmented and mixed reality by providing ideas on how to make learning more effective, how existing VR/AR solutions can be used as learning tools and how a learning process can be structured. The virtual reality (VR) solutions can be used successfully for educational purposes as their use can contribute to the construction of knowledge and the development of metacognitive processes. They also contribute to inclusive education by providing access to knowledge that would not otherwise be available. This book will be of great interest to academics, researchers and post-graduate students in the field of educational technology.
Book Synopsis Photon upconversion heterostructures made from surface-anchored metal-organic frameworks by : Oldenburg, Michael
Download or read book Photon upconversion heterostructures made from surface-anchored metal-organic frameworks written by Oldenburg, Michael and published by KIT Scientific Publishing. This book was released on 2019-01-22 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis X-ray optics made by X-ray lithography: Process optimization and quality control by : Koch, Frieder Johannes
Download or read book X-ray optics made by X-ray lithography: Process optimization and quality control written by Koch, Frieder Johannes and published by KIT Scientific Publishing. This book was released on 2017-10-16 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Grating based X-ray phase contrast imaging sets out to overcome the limits of conventional X-ray imaging in the detection of subtle density differences and opens a way to characterize a sample's microstructure without the need for ultrahigh spatial resolution. The technique relies on grating structures with micrometric periods and extreme aspect ratio - their fabrication by X-ray lithography with optimal structure quality is the topic of this work.
Book Synopsis Bioinspired Superhydrophobic Nano- and Microstructured Surfaces for Drag Reduction and Optoelectronics by : Felix Vüllers
Download or read book Bioinspired Superhydrophobic Nano- and Microstructured Surfaces for Drag Reduction and Optoelectronics written by Felix Vüllers and published by KIT Scientific Publishing. This book was released on 2018-08-29 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Inspired by superhydrophobic leaves of water plants, a flexible superhydrophobic self-cleaning, transparent thin polymeric nanofur film was fabricated through highly scalable hot embossing and hot pulling techniques. Nanofur can retain an air film underwater, whose stability against external stimuli such as high pressure and movement through fluids is investigated. Additionally, the optical properties of nanofur are investigated and exploited to enhance the efficiency of optoelectronic devices.
Book Synopsis MRI of Short and Ultrashort-T_2 Tissues by : Jiang Du
Download or read book MRI of Short and Ultrashort-T_2 Tissues written by Jiang Du and published by Springer Nature. This book was released on 2023 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zusammenfassung: This book comprehensively covers ultrashort echo time (UTE), zero echo time (ZTE), and other magnetic resonance imaging (MRI) acquisition techniques for imaging of short and ultrashort-T2 tissues. MRI uses a large magnet and radio waves to generate images of tissues in the body. The MRI signal is characterized by two time constants, spin-lattice relaxation time (T1) which describes how fast the longitudinal magnetization recovers to its initial value after tipping to the transverse plane, and spin-spin relaxation time (T2) which describes how fast the transverse magnetization decays. Conventional MRI techniques have been developed to image and quantify tissues with relatively long T2s. However, the body also contains many tissues and tissue components such as cortical bone, menisci, ligaments, tendons, the osteochondral junction, calcified tissues, lung parenchyma, iron containing tissues, and myelin, which have short or ultrashort-T2s. These tissues are "invisible" with conventional MRI, and their MR and tissue properties are not measurable. UTE and ZTE type sequences resolve these challenges and make these tissues visible and quantifiable. This book first introduces the basic physics of conventional MRI as well as UTE and ZTE type MRI, including radiofrequency excitation, data acquisition, and image reconstruction. A series of contrast mechanisms are then introduced and these provide high resolution, high contrast imaging of short and ultrashort-T2 tissues. A series of quantitative UTE imaging techniques are described for measurement of MR tissue properties (proton density, T1, T2, T2*, T1p,magnetization transfer, susceptibility, perfusion and diffusion). Finally, clinical applications in the musculoskeletal, neurological, pulmonary and cardiovascular systems are described. This is an ideal guide for physicists and radiologists interested in learning more about the use of UTE and ZTE type techniques for MRI of short and ultrashort-T2 tissues
Book Synopsis MRI of Tissues with Short T2s or T2*s by : Graeme M. Bydder
Download or read book MRI of Tissues with Short T2s or T2*s written by Graeme M. Bydder and published by John Wiley & Sons. This book was released on 2012-12-19 with total page 791 pages. Available in PDF, EPUB and Kindle. Book excerpt: The content of this volume has been added to eMagRes (formerly Encyclopedia of Magnetic Resonance) - the ultimate online resource for NMR and MRI. Up to now MRI could not be used clinically for imaging fine structures of bones or muscles. Since the late 1990s however, the scene has changed dramatically. In particular, Graeme Bydder and his many collaborators have demonstrated the possibility – and importance – of imaging structures in the body that were previously regarded as being “MR Invisible”. The images obtained with a variety of these newly developed methods exhibit complex contrast, resulting in a new quality of images for a wide range of new applications. This Handbook is designed to enable the radiology community to begin their assessment of how best to exploit these new capabilities. It is organised in four major sections – the first of which, after an Introduction, deals with the basic science underlying the rest of the contents of the Handbook. The second, larger, section describes the techniques which are used in recovering the short T2 and T2* data from which the images are reconstructed. The third and fourth sections present a range of applications of the methods described earlier. The third section deals with pre-clinical uses and studies, while the final section describes a range of clinical applications. It is this last section that will surely have the biggest impact on the development in the next few years as the huge promise of Short T2 and T2* Imaging will be exploited to the benefit of patients. In many instances, the authors of an article are the only research group who have published on the topic they describe. This demonstrates that this Handbook presents a range of methods and applications with a huge potential for future developments. About EMR Handbooks / eMagRes Handbooks The Encyclopedia of Magnetic Resonance (up to 2012) and eMagRes (from 2013 onward) publish a wide range of online articles on all aspects of magnetic resonance in physics, chemistry, biology and medicine. The existence of this large number of articles, written by experts in various fields, is enabling the publication of a series of EMR Handbooks / eMagRes Handbooks on specific areas of NMR and MRI. The chapters of each of these handbooks will comprise a carefully chosen selection of articles from eMagRes. In consultation with the eMagRes Editorial Board, the EMR Handbooks / eMagRes Handbooks are coherently planned in advance by specially-selected Editors, and new articles are written (together with updates of some already existing articles) to give appropriate complete coverage. The handbooks are intended to be of value and interest to research students, postdoctoral fellows and other researchers learning about the scientific area in question and undertaking relevant experiments, whether in academia or industry. Have the content of this Handbook and the complete content of eMagRes at your fingertips! Visit: www.wileyonlinelibrary.com/ref/eMagRes View other eMagRes publications here
Book Synopsis Tissue Characterization in MR Imaging by : H. Peter Higer
Download or read book Tissue Characterization in MR Imaging written by H. Peter Higer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: H.P. HIGER 1 In the seventeenth century people dreamed about a machine to get rid of evil spirits and obsessions, which were thought to be the main source of mis fortune and disease. I am not going to question this approach, because in a way it sounds reasonable. They dreamed of a machine that would display im ages from the inner world of men which could be easily identified and named. Somehow these are the roots of MR imaging. Of course, we now view disease from a different point of view but our objectives remain the same, namely to make diseases visible and to try to characterize them in order to cure them. This was the reason for setting up a symposium on tissue characterization. About 300 years later the clinical introduction of MRI has great potential for making this dream come true, and I hope that this symposium has con stituted another step toward its realization. When Damadian published his article in 1971 about differences in T1 relaxation times between healthy and pathological tissues, this was a milestone in tissue characterization. His results initiated intensive research in to MR imaging and tissue parameters. Actually his encouraging discovery was not only the first but also the last for a long time in the field of MR tissue characterization.
Book Synopsis Magnetic Resonance Imaging of Short-T2 Tissues with Applications for Quantifying Cortical Bone Water and Myelin by : Cheng Li
Download or read book Magnetic Resonance Imaging of Short-T2 Tissues with Applications for Quantifying Cortical Bone Water and Myelin written by Cheng Li and published by . This book was released on 2014 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: The human body contains a variety of tissue species with short T2 ranging from a few microseconds to hundreds of microseconds. Detection and quantification of these short- T2 species is of considerable clinical and scientific interest. Cortical bone water and myelin are two of the most important tissue constituents. Quantification of cortical bone water concentration allows for indirect estimation of bone pore volume and noninvasive assessment of bone quality. Myelin is essential for the proper functioning of the central nervous system (CNS). Direct assessment of myelin would reveal CNS abnormalities and enhance our understanding of neurological diseases. However, conventional MRI with echo times of several milliseconds or longer is unable to detect these short-lived MR signals. Recent advances in MRI technology and hardware have enabled development of a number of short- T2 imaging techniques, key among which are ultra-short echo time (UTE) imaging, zero echo time (ZTE) imaging, and sweep imaging with Fourier transform (SWIFT). While these pulse sequences are able to detect short- T2 species, they still suffer from signal interference between different T2 tissue constituents, image artifacts and excessive scan time. These are primary technical hurdles for application to whole-body clinical scanners. In this thesis research, new MRI techniques for improving short- T2 tissue imaging have been developed to address these challenges with a focus on direct detection and quantification of cortical bone water and myelin on a clinical MRI scanner. The first focus of this research was to optimize long- T2 suppression in UTE imaging. Saturation and adiabatic RF pulses were designed to achieve maximum long- T2 suppression while maximizing the signal from short- T2 species. The imaging protocols were optimized by Bloch equation simulations and were validated using phantom and in vivo experiments. The results show excellent short- T2 contrast with these optimized pulse sequences. The problem of blurring artifacts resulting from the inhomogeneous excitation profile of the rectangular pulses in ZTE imaging was addressed. The proposed approach involves quadratic phase-modulated RF excitation and iterative solution of an inverse problem formulated from the signal model of ZTE imaging and is shown to effectively remove the image artifacts. Subsequently image acquisition efficiency was improved in order to attain clinically-feasible scan times. To accelerate the acquisition speed in UTE and ZTE imaging, compressed sensing was applied with a hybrid 3D UTE sequence. Further, the pulse sequence and reconstruction procedure were modified to enable anisotropic field-of-view shape conforming to the geometry of the elongated imaged object. These enhanced acquisition techniques were applied to the detection and quantification of cortical bone water. A new biomarker, the suppression ratio (a ratio image derived from two UTE images, one without and the other with long- T2 suppression), was conceived as a surrogate measure of cortical bone porosity. Experimental data suggest the suppression ratio may be a more direct measure of porosity than previously measured total bone water concentration. Lastly, the feasibility of directly detecting and quantifying spatially-resolved myelin concentration with a clinical imager was explored, both theoretically and experimentally. Bloch equation simulations were conducted to investigate the intrinsic image resolution and the fraction of detectable myelin signal under current scanner hardware constraints. The feasibility of quantitative ZTE imaging of myelin extract and lamb spinal cord at 3T was demonstrated. The technological advances achieved in this dissertation research may facilitate translation of short- T2 MRI methods from the laboratory to the clinic.
Book Synopsis Benzel's Spine Surgery E-Book by : Michael P. Steinmetz
Download or read book Benzel's Spine Surgery E-Book written by Michael P. Steinmetz and published by Elsevier Health Sciences. This book was released on 2021-05-18 with total page 2116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written and edited by world-renowned experts in the field, Benzel’s Spine Surgery: Techniques, Complication Avoidance and Management, 5th Edition, provides expert, step-by-step guidance on the evaluation and management of disorders of the spine. This definitive, two-volume work explores the full spectrum of techniques used in spine surgery, giving you the tools you need to hone your skills and increase your knowledge in this challenging area. Clearly organized and extensively revised throughout, it features contributions from both neurosurgeons and orthopaedic surgeons to present a truly comprehensive approach to spine disease. Offers a thorough overview of the effective management of patients with spinal disorders, including fundamental principles, biomechanics, applied anatomy, instrumentation, pathophysiology of spinal disorders, surgical techniques, motion preservation strategies, non-surgical management, and complication avoidance and management, as well as controversies. Focuses on both pathophysiology and surgical treatment of spine disease, with an increased emphasis on minimally invasive surgery. Contains new features such as key points boxes at the beginning of chapters and algorithms to help streamline the decision making process. Covers today’s hot topics in spine surgery, such as health economics, artificial intelligence, predictive analytics, new less invasive techniques including endoscopic spine surgery, and the future of spine surgery. Provides expert coverage of key topics including biomechanics of motion preservation techniques, spinal injuries in sports, biologics in spine fusion surgery, anterior sub-axial cervical fixation and fusion techniques, complex lumbosacropelvic fixation techniques, and many more. Features more than 1,500 high-quality illustrations, as well as new procedural videos on en bloc spondylectomy, minimally invasive endoscopic posterior cervical foraminotomy, cervical total disc replacement, minimally invasive lumbar decompression of stenosis, and more. Enhanced eBook version included with purchase. Your enhanced eBook allows you to access all of the text, figures, and references from the book on a variety of devices.
Book Synopsis Magnetic Resonance Imaging in Tissue Engineering by : Mrignayani Kotecha
Download or read book Magnetic Resonance Imaging in Tissue Engineering written by Mrignayani Kotecha and published by John Wiley & Sons. This book was released on 2017-02-21 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Resonance Imaging in Tissue Engineering provides a unique overview of the field of non-invasive MRI assessment of tissue engineering and regenerative medicine Establish a dialogue between the tissue-engineering scientists and imaging experts and serves as a guide for tissue engineers and biomaterial developers alike Provides comprehensive details of magnetic resonance imaging (MRI) techniques used to assess a variety of engineered and regenerating tissues and organs Covers cell-based therapies, engineered cartilage, bone, meniscus, tendon, ligaments, cardiovascular, liver and bladder tissue engineering and regeneration assessed by MRI Includes a chapter on oxygen imaging method that predominantly is used for assessing hypoxia in solid tumors for improving radiation therapy but has the ability to provide information on design strategies and cellular viability in tissue engineering regenerative medicine
Book Synopsis Magnetic Resonance Imaging in Orthopedic Sports Medicine by : Robert Pedowitz
Download or read book Magnetic Resonance Imaging in Orthopedic Sports Medicine written by Robert Pedowitz and published by Springer Science & Business Media. This book was released on 2008-10-06 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: This uniquely interdisciplinary book is a practical resource on orthopedic MR imaging that bridges the backgrounds of radiologists and orthopedic surgeons. Radiologists learn why surgeons order imaging studies. They also learn terminology that will help them tailor reports to the specialty. Orthopedic surgeons gain insight on when to order an MRI, how MRI affects decision making, and how to interpret images. Case studies also depict key clinical and exam points, supplemented by MR images and illustrations. Shorter sections highlight other anatomical areas, and additional chapters address diagnostic accuracy and imaging pitfalls.
Book Synopsis Simultaneous Quantitative Multiparametric MRI for In Vivo Tissue Characterization Using Magnetic Resonance Multitasking: Methodology and Clinical Experience by : Sen Ma
Download or read book Simultaneous Quantitative Multiparametric MRI for In Vivo Tissue Characterization Using Magnetic Resonance Multitasking: Methodology and Clinical Experience written by Sen Ma and published by . This book was released on 2020 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: In current clinical systems, magnetic resonance imaging scans for disease diagnosis and prognosis are dominated by qualitative contrast-weighted imaging. These qualitative MR images reveal regional differences in signal intensities between tissues with focal structural or functional abnormalities and tissues that are supposedly in healthy states, facilitating subjective determination for disease diagnosis. The administration of gadolinium-based contrast agents is prevalent in clinical MRI exams, which alternates the relaxation time of neighboring water protons and creates enhanced signal intensities from damaged tissues with high vascular density and thin vessel wall for better visualization. Nowadays, nearly 50% of the MRI studies were conducted with contrast agents. However, patients with renal insufficiency are at risk of developing nephrogenic system fibrosis if exposed to gadolinium-based contrast agents, and chronic toxic effects of possible gadolinium retention have been reported. In the meantime, qualitative contrast-weighted images have limited sensitivity to subtle alteration in tissue states, lack of biological specificity and multi-center reproducibility, and limited predictive values. One promising alternative is quantitative multiparametric MRI, which contains various methods to quantify multiple parameters with interpretable physical units that are intrinsic to tissue properties. Most of these quantitative approaches do not involve the administration of contrast agents, therefore ensuring the safety of the application to a wide range of patients and reducing the costs of MRI. These quantitative parameters are highly reproducible, sensitive to subtle physiological tissue changes, and specific for disease pathologies. More importantly, each of these parameters reveal tissue properties in different aspects, having the potential to offer complementary information for comprehensive tissue characterization, and acting as biomarkers that are directly associated with diseases states. Despite the benefits to clinical studies, quantitative multiparametric MRI has yet to be widely adopted in routine clinical practices because of several major technical limitations including (i) long scan times that compromises image resolution and/or spatial coverage, (ii) motion artifacts, (iii) misaligned parametric maps due to separate acquisitions, and (iv) complicated clinical workflow. This dissertation aims to address some of these challenges by proposing a simultaneous quantitative multiparametric MRI approach with Magnetic Resonance Multitasking and focus on the quantification of T1, T2, T1 , and ADC, which serves as the start of the ultimate goal to provide a clinically translatable, multiparametric whole-body quantitative tissue characterization technique. A novel approach to simultaneously quantifying T1, T2, and ADC in the brain was first developed using MR Multitasking in conjunction with a time-resolved phase correction strategy to compensate for the inter-shot phase inconsistencies introduced by physiological motion. It was implemented as a push-button, continuous acquisition that simplified the workflow. This technique was initially demonstrated in healthy subjects to efficiently produce distortion-free, co-registered T1, T2, and ADC maps with 3D brain coverage (100mm) in 9.3min. The resulting T1, T2, and ADC measurements in the brain were comparable to reference quantitative approaches. Abrupt motion was manually identified and removed to yield T1, T2, and ADC maps that were free from motion artifacts and with accurate quantitative measurements. Clinical feasibility was demonstrated on post-surgery glioblastoma patients. A motion-resolved, simultaneous T1, T2, and T1 quantification technique was then developed using MR Multitasking in a push-button 9min acquisition. Rigid intra-scan head motion was captured and simultaneously resolved along with the relaxation processes. This technique was first validated in healthy subjects to produce high quality, whole-brain (140mm) T1, T2, and T1 maps and repeatable T1, T2, and T1 measurements that were in excellent agreement with gold standard methods. Motion-resolved, artifact-free maps were generated under either in-plane or through-plane motion, which provided a novel avenue for handling rigid motion in brain MRI. Synthetic contrast-weighted qualitative images comparable to clinical images were generated using the parameter maps, demonstrating the significant potential to replace conventional MRI scans with a single Multitasking scan for clinical purposes. This technique was applied in a pilot clinical setting to perform tissue characterization in relapsing-remitting multiple sclerosis patients. The combination of T1, T2, and T1 significantly improved the accuracy of the differentiation of multiple sclerosis patients from healthy controls, compared to either single parameter alone, indicating the clinical utility of T1, T2, and T1 as quantitative biomarkers. Lastly, the above two quantitative techniques were extended to other body organs for a preliminary demonstration of potential applications, where we 1) simultaneously quantified T1, T2, and ADC in the breast with whole-breast coverage (160mm) in 8min, incorporating a B1+-compensated multiparametric fitting approach to address the notable B1+ inhomogeneity across the bilateral breast FOV, and to provide distortion-free, co-registered whole-breast T1, T2, and ADC maps with good in vivo repeatability; and 2) simultaneously quantified myocardial T1 and T1 in a single non-ECG, free-breathing acquisition, where cardiac motion and respiratory motion were retrospectively identified and simultaneously resolved to produce dynamic myocardial T1 and T1 maps of 20 cardiac phases with high temporal resolution (15ms) in a single, continuous acquisition of 1.5min per slice. Multitasking T1 and T1 measurements in the heart were comparable with gold standard techniques.
Book Synopsis Magnetic Resonance Imaging of Engineered Tissues by : Sun (Y.)
Download or read book Magnetic Resonance Imaging of Engineered Tissues written by Sun (Y.) and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis New Techniques and Optimizations of Short Echo-time 1H MRI with Applications in Murine Lung by : Jinbang Guo
Download or read book New Techniques and Optimizations of Short Echo-time 1H MRI with Applications in Murine Lung written by Jinbang Guo and published by . This book was released on 2016 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although x-ray computed tomography (CT) is a gold standard for pulmonary imaging, it has high ionizing radiation, which puts patients at greater risk of cancer, particularly in a longitudinal study with cumulative doses. Magnetic resonance imaging (MRI) doesn't involve exposure to ionizing radiation and is especially useful for visualizing soft tissues and organs such as ligaments, cartilage, brain, and heart. Many efforts have been made to apply MRI to study lung function and structure of both humans and animals. However, lung is a unique organ and is very different from other solid organs like the heart and brain due to its complex air-tissue interleaved structure. The magnetic susceptibility differences at the air-tissue interfaces result in very short T2* (~1 ms) of lung parenchyma, which is even shorter in small-animal MRI (often at higher field) than in human MRI. Both low proton density and short T2* of lung parenchyma are challenges for pulmonary imaging via MRI because they lead to low signal-to-noise ratio (SNR) in images with traditional Cartesian methods that necessitate longer echo times ({u2265} 1 ms). This dissertation reports the work of optimizing pulmonary MRI techniques by minimizing the negative effects of low proton density and short T2* of murine lung parenchyma, and the application of these techniques to imaging murine lung. Specifically, echo time (TE) in the Cartesian sequence is minimized, by simultaneous slice select rephasing, phase encoding and read dephasing gradients, in addition to partial Fourier imaging, to reduce signal loss due to T2* relaxation. Radial imaging techniques, often called ultra-short echo-time MRI or UTE MRI, with much shorter time between excitation and data acquisition, were also developed and optimized for pulmonary imaging. Offline reconstruction for UTE data was developed on a Linux system to regrid the non-Cartesian (radial in this dissertation) k-space data for fast Fourier transform. Slab-selected UTE was created to fit the field-of-view (FOV) to the imaged lung without fold-in aliasing, which increases TE slightly compared to non-slab-selected UTE. To further reduce TE as well as fit the FOV to the lung without aliasing, UTE with ellipsoidal k-space coverage was developed, which increases resolution and decreases acquisition time. Taking into account T2* effects, point spread function (PSF) analysis was performed to determine the optimal acquisition time for maximal single-voxel SNR. Retrospective self-gating UTE was developed to avoid the use of a ventilator (which may cause lung injury) and to avoid possible prospective gating errors caused by abrupt body motion. Cartesian gradient-recalled-echo imaging (GRE) was first applied to monitor acute cellular rejection in lung transplantation. By repeated imaging in the same animals, both parenchymal signal and lung compliance were measured and were able to detect rejection in the allograft lung. GRE was also used to monitor chronic cellular rejection in a transgenic mouse model after lung transplantation. In addition to parenchymal signal and lung compliance, the percentage of high-density lung parenchyma was defined and measured to detect chronic rejection. This represents one of the first times quantitative pulmonary MRI has been performed. For 3D radial UTE MRI, 2D golden means (1) were used to determine the direction of radial spokes in k-space, resulting in pseudo-random angular sampling of spherical k-space coverage. Ellipsoidal k-space coverage was generated by expanding spherical coverage to create an ellipsoid in k-space. UTE MRI with ellipsoidal k-space coverage was performed to image healthy mice and phantoms, showing reduced FOV and enhanced in-plane resolution compared to regular UTE. With this modified UTE, T2* of lung parenchyma was measured by an interleaved multi-TE strategy, and T1 of lung parenchyma was measured by a limited flip angle method (2). Retrospective self-gating UTE with ellipsoidal k-space coverage was utilized to monitor the progression of pulmonary fibrosis in a transforming growth factor (TGF)-[alpha] transgenic mouse model and compared with histology and pulmonary mechanics. Lung fibrosis progression was not only visualized by MRI images, but also quantified and tracked by the MRI-derived lung function parameters like mean lung parenchyma signal, high-density lung volume percentage, and tidal volume. MRI-derived lung function parameters were strongly correlated with the findings of pulmonary mechanics and histology in measuring fibrotic burden. This dissertation demonstrates new techniques and optimizations in GRE and UTE MRI that are employed to minimize TE and image murine lungs to assess lung function and structure and monitor the time course of lung diseases. Importantly, the ability to longitudinally image individual animals by these MRI techniques minimizes the number of animals required in preclinical studies and increases the statistical power of future experiments as each animal can serve at its own control.
Book Synopsis MRI of the Lung by : Hans-Ulrich Kauczor
Download or read book MRI of the Lung written by Hans-Ulrich Kauczor and published by Springer Science & Business Media. This book was released on 2008-11-12 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past decade significant developments have been achieved in the field of magnetic resonance imaging (MRI), enabling MRI to enter the clinical arena of chest imaging. Standard protocols can now be implemented on up-to-date scanners, allowing MRI to be used as a first-line imaging modality for various lung diseases, including cystic fibrosis, pulmonary hypertension and even lung cancer. The diagnostic benefits stem from the ability of MRI to visualize changes in lung structure while simultaneously imaging different aspects of lung function, such as perfusion, respiratory motion, ventilation and gas exchange. On this basis, novel quantitative surrogates for lung function can be obtained. This book provides a comprehensive overview of how to use MRI for imaging of lung disease. Special emphasis is placed on benign diseases requiring regular monitoring, given that it is patients with these diseases who derive the greatest benefit from the avoidance of ionizing radiation.
