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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: 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: 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: Stefan O. Schönberg Publisher: Springer Science & Business Media ISBN: 354068879X Category : Medical Languages : en Pages : 548
Book Description
This book presents the first in-depth introduction to parallel imaging techniques and, in particular, to the application of parallel imaging in clinical MRI. It will provide readers with a broader understanding of the fundamental principles of parallel imaging and of the advantages and disadvantages of specific MR protocols in clinical applications in all parts of the body at 1.5 and 3 Tesla.
Author: Derek K Jones Publisher: Oxford University Press ISBN: 0199708703 Category : Science Languages : en Pages : 784
Book Description
Professor Derek Jones, a world authority on diffusion MRI, has assembled most of the world's leading scientists and clinicians developing and applying diffusion MRI to produce an authorship list that reads like a "Who's Who" of the field and an essential resource for those working with diffusion MRI. Destined to be a modern classic, this definitive and richly illustrated work covers all aspects of diffusion MRI from basic theory to clinical application. Oxford Clinical Neuroscience is a comprehensive, cross-searchable collection of resources offering quick and easy access to eleven of Oxford University Press's prestigious neuroscience texts. Joining Oxford Medicine Online these resources offer students, specialists and clinical researchers the best quality content in an easy-to-access format.
Author: Julien Cohen-Adad Publisher: Academic Press ISBN: 0123972825 Category : Medical Languages : en Pages : 331
Book Description
Quantitative MRI of the Spinal Cord is the first book focused on quantitative MRI techniques with specific application to the human spinal cord. This work includes coverage of diffusion-weighted imaging, magnetization transfer imaging, relaxometry, functional MRI, and spectroscopy. Although these methods have been successfully used in the brain for the past 20 years, their application in the spinal cord remains problematic due to important acquisition challenges (such as small cross-sectional size, motion, and susceptibility artifacts). To date, there is no consensus on how to apply these techniques; this book reviews and synthesizes state-of-the-art methods so users can successfully apply them to the spinal cord. Quantitative MRI of the Spinal Cord introduces the theory behind each quantitative technique, reviews each theory’s applications in the human spinal cord and describes its pros and cons, and suggests a simple protocol for applying each quantitative technique to the spinal cord. Chapters authored by international experts in the field of MRI of the spinal cord Contains “cooking recipes —examples of imaging parameters for each quantitative technique—designed to aid researchers and clinicians in using them in practice Ideal for clinical settings
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: Susumu Mori Publisher: Academic Press ISBN: 0123984076 Category : Medical Languages : en Pages : 141
Book Description
The concepts behind diffusion tensor imaging (DTI) are commonly difficult to grasp, even for magnetic resonance physicists. To make matters worse, a many more complex higher-order methods have been proposed over the last few years to overcome the now well-known deficiencies of DTI. In Introduction to Diffusion Tensor Imaging: And Higher Order Models, these concepts are explained through extensive use of illustrations rather than equations to help readers gain a more intuitive understanding of the inner workings of these techniques. Emphasis is placed on the interpretation of DTI images and tractography results, the design of experiments, and the types of application studies that can be undertaken. Diffusion MRI is a very active field of research, and theories and techniques are constantly evolving. To make sense of this constantly shifting landscape, there is a need for a textbook that explains the concepts behind how these techniques work in a way that is easy and intuitive to understand—Introduction to Diffusion Tensor Imaging fills this gap. Extensive use of illustrations to explain the concepts of diffusion tensor imaging and related methods Easy to understand, even without a background in physics Includes sections on image interpretation, experimental design, and applications Up-to-date information on more recent higher-order models, which are increasingly being used for clinical applications
Author: Heidi Johansen-Berg Publisher: Academic Press ISBN: 0124055095 Category : Medical Languages : en Pages : 627
Book Description
Diffusion MRI remains the most comprehensive reference for understanding this rapidly evolving and powerful technology and is an essential handbook for designing, analyzing, and interpreting diffusion MR experiments. Diffusion imaging provides a unique window on human brain anatomy. This non-invasive technique continues to grow in popularity as a way to study brain pathways that could never before be investigated in vivo. This book covers the fundamental theory of diffusion imaging, discusses its most promising applications to basic and clinical neuroscience, and introduces cutting-edge methodological developments that will shape the field in coming years. Written by leading experts in the field, it places the exciting new results emerging from diffusion imaging in the context of classical anatomical techniques to show where diffusion studies might offer unique insights and where potential limitations lie. Fully revised and updated edition of the first comprehensive reference on a powerful technique in brain imaging Covers all aspects of a diffusion MRI study from acquisition through analysis to interpretation, and from fundamental theory to cutting-edge developments New chapters covering connectomics, advanced diffusion acquisition, artifact removal, and applications to the neonatal brain Provides practical advice on running an experiment Includes discussion of applications in psychiatry, neurology, neurosurgery, and basic neuroscience Full color throughout