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Author: Jiang Du
Publisher: Springer Nature
ISBN: 3031351975
Category : Electronic books
Languages : en
Pages : 612
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Book Description
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
Author: Jiang Du
Publisher: Springer Nature
ISBN: 3031351975
Category : Electronic books
Languages : en
Pages : 612
Get Book Here
Book Description
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
Author: Graeme M. Bydder
Publisher: John Wiley & Sons
ISBN: 1118590511
Category : Medical
Languages : en
Pages : 791
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Book Description
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
Author: Cheng Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 254
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Book Description
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.
Author: Oezen, Ali Caglar
Publisher: KIT Scientific Publishing
ISBN: 3731506572
Category : Diagnosis
Languages : en
Pages : 266
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Book Description
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.
Author: Hans-Ulrich Kauczor
Publisher: Springer Science & Business Media
ISBN: 354034618X
Category : Medical
Languages : en
Pages : 315
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Book Description
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.
Author: Thomas M. Link
Publisher: Springer Science & Business Media
ISBN: 1441984380
Category : Medical
Languages : en
Pages : 253
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Book Description
This authoritative book provides state-of-the-art practices and new developments in the imaging of cartilage, associated pathologies, and repair procedures. With a main focus on MRI, major advances in cartilage imaging are put into clinical context relevant for radiologists, rheumatologists, and orthopedic surgeons. International experts provide their insights on cartilage pathologies associated with such conditions as osteoarthritis, osteochondral trauma, and cartilage repair. Morphological MRI techniques are outlined, including new sequences and high field imaging. Molecular imaging techniques able to characterize the biochemical composition of the cartilage matrix are discussed, such as T2 relaxation time, T1rho, and dGEMRIC methods. The first book of its kind, Cartilage Imaging: Significance, Techniques, and New Developments encompasses the full scope of knowledge in this rapidly evolving field. Identifying key techniques for characterizing disease processes as well as objectively and quantitatively evaluating the results of therapy, this outstanding resource is of benefit to all physicians interested in assessing cartilage disease and repair.
Author: Agazi Tesfai
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: E. Mark Haacke
Publisher: John Wiley & Sons
ISBN: 111814807X
Category : Medical
Languages : en
Pages : 817
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Book Description
MRI Susceptibility Weighted Imaging discusses the promising new MRI technique called Susceptibility Weighted Imaging (SWI), a powerful tool for the diagnosis and treatment of acute stroke, allowing earlier detection of acute stroke hemorrhage and easier detection of microbleeds in acute ischemia. The book is edited by the originators of SWI and features contributions from the top leaders in the science. Presenting an even balance between technical/scientific aspects of the modality and clinical application, this book includes over 100 super high-quality radiographic images and 100 additional graphics and tables.
Author: Adrienne Grace Siu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Cameron Kerl
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
INTRODUCTION: Magnetic resonance imaging (MRI) is useful for confirming the clinical diagnosis of rotator cuff tears; however, traditional MR sequences have the limitation of being insensitive to small changes in tendon architecture in the absence of a gross tendon defect. MR sequences utilizing ultra-short time to echo (UTE) allow for in vivo assessment of connective tissue architecture that could only otherwise be ascertained through direct tissue biopsy. Ongoing research at our institution has demonstrated longitudinal tissue-specific patterns of remodeling of autograft tissue following anterior cruciate ligament reconstruction with serial UTE-T2* MR imaging that is not visible with traditional MR sequences. We believe this conceptual framework can be applied to the assessment of rotator cuff tendon quality following surgical repair. As reliability studies are required to validate and interpret the results of promising new diagnostic imaging technologies, the purpose of this study was to determine the inter-observer reliability and test-retest reliability of T2* mapping of the supraspinatus tendon with respect to final calculated T2* values resulting from UTE MR sequences. We hypothesized that T2* mapping of the supraspinatus tendon would produce good-to-excellent inter-observer reliability and test-retest reliability with respect to final calculated T2* values.METHODS: After IRB approval, 7 patients who underwent shoulder UTE-MRI scans for reasons other than rotator cuff pathology were retrospectively retrieved for analysis. Scans were performed on a Philips Ingenia 3T system. Sequences included a high-resolution 3D T2 scan (slice thickness: 0.6mm, TR: 18.7ms; TE: 11.5ms) and a quad-echo T2 UTE sequence (slice thickness: 1mm, TR: 20ms; TE: 0.3, 3, 6, 9 ms). Using 3D tissue segmentation software (Mimics; Materialise, Inc), four independent observers segmented the supraspinatus tendon in each of the 7 scans using coronal slices within proton-density T2 sequences on two occasions separated by at least two weeks. In the coronal plane, segmentation of the supraspinatus tendon spanned from the most distal insertion site to the most medial aspect of the humeral head, and within the boundaries formed by the largest width of the humeral head and glenoid in the axial plane. 3D reconstructions were created for each segmentation mask, and 3D model was co-registered with, and transferred to, the calculated UTE-T2* maps that were obtained simultaneously with the traditional MR sequences. New segmentation masks were then calculated from the 3D model corresponding with the identical voxels segmented on the traditional MR sequence. Reliability calculations were then performed with respective to average T2* values underlying the segmented regions of interest corresponding to the supraspinatus tendon. Customized software was created using Python to extract average T2* values underlying each segmented region of interest. Inter-observer reliability was calculated using Pearson correlation coefficients and plotted using a statistical control chart spanning u00b1 3 standard deviations. Intra-observer reliability was calculated using intra-class correlation coefficients (Fleiss u03ba) with 95% confidence intervals. P
