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Author: Franz Schmitt Publisher: Springer Science & Business Media ISBN: 3642804438 Category : Medical Languages : en Pages : 754
Book Description
"Dost thou love life? Then do not squander time, for that's the stuff life is made oj': Benjamin Franklin This book describes the technical principles and applications of echo-planar imaging (EPI) which, as much as any other technique, has shaped the develop ment of modern magnetic resonance imaging (MRI). The principle of EPI, namely, the acquisition of multiple nuclear magnetic resonance echoes from a single spin excitation, has made it possible to shorten the previously time-con suming MRI data acquisition from minutes to much less than a second. Interest ingly, EPI is one of the oldest MRI techniques, conceived in 1976 by Sir Peter Mansfield only 4 years after the initial description of the principles of MRI. One of the inventors of MRI himself, Mansfield realized that fast data acquisition would be paramount in bringing medical applications of MRI to full fruition. The technological challenges in implementing EPI, however, were formidable. Until the end of the 1980s few people believed that EPI would be clinically useful, since its complexity was far greater than that of "conventional" MRI methods.
Author: Franz Schmitt Publisher: Springer Science & Business Media ISBN: 3642804438 Category : Medical Languages : en Pages : 754
Book Description
"Dost thou love life? Then do not squander time, for that's the stuff life is made oj': Benjamin Franklin This book describes the technical principles and applications of echo-planar imaging (EPI) which, as much as any other technique, has shaped the develop ment of modern magnetic resonance imaging (MRI). The principle of EPI, namely, the acquisition of multiple nuclear magnetic resonance echoes from a single spin excitation, has made it possible to shorten the previously time-con suming MRI data acquisition from minutes to much less than a second. Interest ingly, EPI is one of the oldest MRI techniques, conceived in 1976 by Sir Peter Mansfield only 4 years after the initial description of the principles of MRI. One of the inventors of MRI himself, Mansfield realized that fast data acquisition would be paramount in bringing medical applications of MRI to full fruition. The technological challenges in implementing EPI, however, were formidable. Until the end of the 1980s few people believed that EPI would be clinically useful, since its complexity was far greater than that of "conventional" MRI methods.
Author: Bin Xie Publisher: Open Dissertation Press ISBN: 9781361038666 Category : Echo-planar imaging Languages : en Pages : 117
Book Description
This dissertation, "Echo Planar Imaging Artifact Correction With Parallel Imaging" by Bin, Xie, 解斌, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Echo planar imaging (EPI) is a fast imaging technique that has been widely used in various MRI applications, such diffusion, perfusion and functional magnetic resonance imaging (fMRI). However, the EPI image quality is intrinsically hindered by three major artifacts, i.e., Nyquist ghost, geometric distortion and fat residue. The main objective of this dissertation is to investigate and develop novel methods to correct different EPI artifacts using parallel imaging. Firstly, a new Nyquist ghost and geometric distortion correction method using parallel imaging was proposed in EPI. This method calibrates the parallel imaging from two frames of EPI acquired with different phase labels. Then Nyquist ghost is subsequently removed by reconstructing images from only positive or negative echoes. Meanwhile, this phase labeling strategy shifts the TE of the second frame and allows the B0 field map generation from positive and negative images for distortion correction. The phantom results at 7T and 3T demonstrated that our method could greatly reduce Nyquist ghost even under oblique imaging and poor eddy current conditions, yielding significant improvements over the existing reference scan and image entropy minimization methods, and eliminate the geometric distortion simultaneously. The phantom results indicated that the SNR efficiency was largely preserved while the fMRI results showed no apparent degradation of temporal resolution. Secondly, in order to further improve the SNR performance of parallel imaging in Nyquist ghost correction, a new method which incorporates phase error correction with sensitivity encoding (SENSE) was proposed. This method reconstructs two Nyquist ghost free images from positive or negative echo, and then estimates a phase error map from these two images. Phase error correction is subsequently incorporated into SENSE to reconstruct the final Nyquist ghost free images. Results from phantom and human brain experiments demonstrated that this method was as robust as the other parallel imaging based Nyquist ghost correction techniques even under oblique imaging and poor eddy current conditions. Moreover, SNR measurements in both phantom and in vivo studies suggested that this method did not suffer from noise amplification and provided larger signal-to-noise ratio (SNR) than the others similar parallel imaging based Nyquist ghost correction techniques. Lastly, the parallel imaging was applied to separate water and fat signal in EPI images. This method utilizes the intrinsic chemical shift property of fat. It treats the water and shifted fat signal in composite EPI images as two simultaneously excited images, which are separated by parallel imaging. Two parallel imaging reconstruction algorithms were applied and evaluated for water and fat separation. The human brain EPI results demonstrated the feasibility of using parallel imaging to separate water and fat signal by both algorithms. This method was further applied to brain and liver diffusion weighted imaging, and the results demonstrated it can be used to remove the undesired fat residual signal. In summary, these studies have demonstrated parallel imaging can be used for EPI artifacts correction and benefit EPI-based applications. Subjects: Echo-planar imaging
Author: Donald W. McRobbie Publisher: Cambridge University Press ISBN: 1316688259 Category : Medical Languages : en Pages : 405
Book Description
MR is a powerful modality. At its most advanced, it can be used not just to image anatomy and pathology, but to investigate organ function, to probe in vivo chemistry, and even to visualise the brain thinking. However, clinicians, technologists and scientists struggle with the study of the subject. The result is sometimes an obscurity of understanding, or a dilution of scientific truth, resulting in misconceptions. This is why MRI from Picture to Proton has achieved its reputation for practical clarity. MR is introduced as a tool, with coverage starting from the images, equipment and scanning protocols and traced back towards the underlying physics theory. With new content on quantitative MRI, MR safety, multi-band excitation, Dixon imaging, MR elastography and advanced pulse sequences, and with additional supportive materials available on the book's website, this new edition is completely revised and updated to reflect the best use of modern MR technology.
Author: Bin Xie Publisher: Open Dissertation Press ISBN: 9781361038673 Category : Technology & Engineering Languages : en Pages : 144
Book Description
This dissertation, "Echo Planar Imaging Artifact Correction With Parallel Imaging" by Bin, Xie, 解斌, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Echo planar imaging (EPI) is a fast imaging technique that has been widely used in various MRI applications, such diffusion, perfusion and functional magnetic resonance imaging (fMRI). However, the EPI image quality is intrinsically hindered by three major artifacts, i.e., Nyquist ghost, geometric distortion and fat residue. The main objective of this dissertation is to investigate and develop novel methods to correct different EPI artifacts using parallel imaging. Firstly, a new Nyquist ghost and geometric distortion correction method using parallel imaging was proposed in EPI. This method calibrates the parallel imaging from two frames of EPI acquired with different phase labels. Then Nyquist ghost is subsequently removed by reconstructing images from only positive or negative echoes. Meanwhile, this phase labeling strategy shifts the TE of the second frame and allows the B0 field map generation from positive and negative images for distortion correction. The phantom results at 7T and 3T demonstrated that our method could greatly reduce Nyquist ghost even under oblique imaging and poor eddy current conditions, yielding significant improvements over the existing reference scan and image entropy minimization methods, and eliminate the geometric distortion simultaneously. The phantom results indicated that the SNR efficiency was largely preserved while the fMRI results showed no apparent degradation of temporal resolution. Secondly, in order to further improve the SNR performance of parallel imaging in Nyquist ghost correction, a new method which incorporates phase error correction with sensitivity encoding (SENSE) was proposed. This method reconstructs two Nyquist ghost free images from positive or negative echo, and then estimates a phase error map from these two images. Phase error correction is subsequently incorporated into SENSE to reconstruct the final Nyquist ghost free images. Results from phantom and human brain experiments demonstrated that this method was as robust as the other parallel imaging based Nyquist ghost correction techniques even under oblique imaging and poor eddy current conditions. Moreover, SNR measurements in both phantom and in vivo studies suggested that this method did not suffer from noise amplification and provided larger signal-to-noise ratio (SNR) than the others similar parallel imaging based Nyquist ghost correction techniques. Lastly, the parallel imaging was applied to separate water and fat signal in EPI images. This method utilizes the intrinsic chemical shift property of fat. It treats the water and shifted fat signal in composite EPI images as two simultaneously excited images, which are separated by parallel imaging. Two parallel imaging reconstruction algorithms were applied and evaluated for water and fat separation. The human brain EPI results demonstrated the feasibility of using parallel imaging to separate water and fat signal by both algorithms. This method was further applied to brain and liver diffusion weighted imaging, and the results demonstrated it can be used to remove the undesired fat residual signal. In summary, these studies have demonstrated parallel imaging can be used for EPI artifacts correction and benefit EPI-based applications. Subjects: Echo-planar imaging
Author: Matt A. Bernstein Publisher: Elsevier ISBN: 0080533124 Category : Mathematics Languages : en Pages : 1041
Book Description
Magnetic Resonance Imaging (MRI) is among the most important medical imaging techniques available today. There is an installed base of approximately 15,000 MRI scanners worldwide. Each of these scanners is capable of running many different "pulse sequences", which are governed by physics and engineering principles, and implemented by software programs that control the MRI hardware. To utilize an MRI scanner to the fullest extent, a conceptual understanding of its pulse sequences is crucial. Handbook of MRI Pulse Sequences offers a complete guide that can help the scientists, engineers, clinicians, and technologists in the field of MRI understand and better employ their scanner. Explains pulse sequences, their components, and the associated image reconstruction methods commonly used in MRI Provides self-contained sections for individual techniques Can be used as a quick reference guide or as a resource for deeper study Includes both non-mathematical and mathematical descriptions Contains numerous figures, tables, references, and worked example problems
Author: Christopher Clarke Publisher: ISBN: 9781999988524 Category : Languages : en Pages : 320
Book Description
Comprehensive medical imaging physics notes aimed at those sitting the first FRCR physics exam in the UK and covering the scope of the Royal College of Radiologists syllabus. Written by Radiologists, the notes are concise and clearly organised with 100's of beautiful diagrams to aid understanding. The notes cover all of radiology physics, including basic science, x-ray imaging, CT, ultrasound, MRI, molecular imaging, and radiation dosimetry, protection and legislation. Although aimed at UK radiology trainees, it is also suitable for international residents taking similar examinations, postgraduate medical physics students and radiographers. The notes provide an excellent overview for anyone interested in the physics of radiology or just refreshing their knowledge. This third edition includes updates to reflect new legislation and many new illustrations, added sections, and removal of content no longer relevent to the FRCR physics exam. This edition has gone through strict critique and evaluation by physicists and other specialists to provide an accurate, understandable and up-to-date resource. The book summarises and pulls together content from the FRCR Physics Notes at Radiology Cafe and delivers it as a paperback or eBook for you to keep and read anytime. There are 7 main chapters, which are further subdivided into 60 sub-chapters so topics are easy to find. There is a comprehensive appendix and index at the back of the book.
Author: Robert W. Brown Publisher: John Wiley & Sons ISBN: 0471720852 Category : Medical Languages : en Pages : 976
Book Description
New edition explores contemporary MRI principles and practices Thoroughly revised, updated and expanded, the second edition of Magnetic Resonance Imaging: Physical Principles and Sequence Design remains the preeminent text in its field. Using consistent nomenclature and mathematical notations throughout all the chapters, this new edition carefully explains the physical principles of magnetic resonance imaging design and implementation. In addition, detailed figures and MR images enable readers to better grasp core concepts, methods, and applications. Magnetic Resonance Imaging, Second Edition begins with an introduction to fundamental principles, with coverage of magnetization, relaxation, quantum mechanics, signal detection and acquisition, Fourier imaging, image reconstruction, contrast, signal, and noise. The second part of the text explores MRI methods and applications, including fast imaging, water-fat separation, steady state gradient echo imaging, echo planar imaging, diffusion-weighted imaging, and induced magnetism. Lastly, the text discusses important hardware issues and parallel imaging. Readers familiar with the first edition will find much new material, including: New chapter dedicated to parallel imaging New sections examining off-resonance excitation principles, contrast optimization in fast steady-state incoherent imaging, and efficient lower-dimension analogues for discrete Fourier transforms in echo planar imaging applications Enhanced sections pertaining to Fourier transforms, filter effects on image resolution, and Bloch equation solutions when both rf pulse and slice select gradient fields are present Valuable improvements throughout with respect to equations, formulas, and text New and updated problems to test further the readers' grasp of core concepts Three appendices at the end of the text offer review material for basic electromagnetism and statistics as well as a list of acquisition parameters for the images in the book. Acclaimed by both students and instructors, the second edition of Magnetic Resonance Imaging offers the most comprehensive and approachable introduction to the physics and the applications of magnetic resonance imaging.