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Author: Arjun Arunachalam
Publisher:
ISBN:
Category :
Languages : en
Pages : 120
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Book Description
Author: Arjun Arunachalam
Publisher:
ISBN:
Category :
Languages : en
Pages : 120
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Book Description
Author: Ziwu Zhou
Publisher:
ISBN:
Category :
Languages : en
Pages : 180
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Book Description
Magnetic resonance imaging (MRI) is a powerful diagnostic medical imaging technique that provides very high spatial resolution. By manipulating the signal evolution through careful imaging sequence design, MRI can generate a wide range of soft-tissue contrast unique to individual application. However, imaging speed remains an issue for many applications. In order to increase scan output without compromising the image quality, the data acquisition and image reconstruction methods need to be designed to fit each application to achieve maximum efficiency. This dissertation concerns several application-tailored accelerated imaging methods through improved sequence design, efficient k-space traverse, as well as tailored image reconstruction algorithm, all together aiming to exploit the full potential of data acquisition and image reconstruction in each application. The first application is ferumoxtyol-enhanced 4D multi-phase cardiovascular MRI on pediatric patients with congenital heart disease. By taking advantage of the high signal-to-noise ratio (SNR) results from contrast enhancement, we introduced two methods to improve the scan efficiency with maintained clinical utility: one with reduced scan time and one with improved temporal resolution. The first method used prospective Poisson-disc under-sampling in combination with graphics processing unit accelerated parallel imaging and compressed sensing combined reconstruction algorithm to reduce scan time by approximately 50% while maintaining highly comparable image quality to un-accelerated acquisition in a clinically practical reconstruction time. The second method utilized a motion weighted reconstruction technique to increase temporal resolution of acquired data, and thus permits improved cardiac functional assessment. Compared with existing acceleration method, the proposed method has nearly three times lower computation burden and six times faster reconstruction speed, all with equal image quality. The second application is noncontrast-enhanced 4D intracranial MR angiography with arterial spin labeling (ASL). Considering the inherently low SNR of ASL signal, we proposed to sample k-space with the efficient golden-angle stack-of-stars trajectory and reconstruct images using compressed sensing with magnitude subtraction as regularization. The acquisition and reconstruction strategy in combination produces images with detailed vascular structures and clean background. At the same time, it allows a reduced temporal blurring delineation of the fine distal arteries when compared with the conventional k-space weighted image contrast (KWIC) reconstruction. Stands upon on this, we further developed an improved stack-of-stars radial sampling strategy for reducing streaking artifacts in general volumetric MRI. By rotating the radial spokes in a golden angle manner along the partition-encoding direction, the aliasing pattern due to under-sampling is modified, resulting in improved image quality for gridding and more advanced reconstruction methods. The third application is low-latency real-time imaging. To achieve sufficient frame rate, real-time MRI typically requires significant k-space under-sampling to accelerate the data acquisition. At the same time, many real-time application, such as interventional MRI, requires user interaction or decision making based on image feedback. Therefore, low-latency on-the-fly reconstruction is highly desirable. We proposed a parallel imaging and convolutional neural network combined image reconstruction framework for low-latency and high quality reconstruction. This is achieved by compacting gradient descent steps resolved from conventional parallel imaging reconstruction as network layers and interleaved with convolutional layers in a general convolutional neural network. Once all parameters of the network are determined during the off-line training process, it can be applied to unseen data with less than 100ms reconstruction time per frame, while more than 1s is usually needed for conventional parallel imaging and compressed sensing combined reconstruction.
Author: Tao Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Magnetic resonance imaging (MRI) is a powerful medical imaging modality widely used in clinical practice. MRI provides excellent soft-tissue contrast, and does not involve ionizing radiation. In an ideal clinical setting for MRI, several requirements have to be met. First of all, diagnostic image quality has to be achieved. Second, fast image reconstruction is required, so that the radiologists can review the images before releasing the patients. Third, fast data acquisition is desired. Short scan time can not only improve patient comfort, but also reduce many imaging artifacts and improve image quality. While advanced methods, such as parallel imaging and compressed sensing, can accelerate MRI data acquisition to some extent, the achievable scan time is still very limited for several MR applications. Meanwhile, the reconstruction time for these advanced methods can take up to hours, and become clinically infeasible. This dissertation describes approaches to maintain a clinically feasible reconstruction time for advanced reconstructions, and approaches to further accelerate MRI applications, specifically MR parameter mapping and dynamic contrast-enhanced (DCE) MRI. The ultimate goal of this work is to make MRI more clinically practical. To maintain a clinically feasible reconstruction time for advanced reconstructions with large coil arrays, a geometric-decomposition coil compression method is proposed. The proposed method exploits the spatially varying data redundancy of large coil arrays, and can compress the raw data from original coils into very few virtual coils. The advanced reconstruction can be directly performed on the virtual coils instead of the original coils. The reconstruction time for large 3D datasets, acquired with 32-channel coils and reconstructed by a combined parallel imaging compressed sensing method, can be reduced to under a minute. The proposed method has been implemented in Lucile Packard Children's Hospital at Stanford. The clinical evaluation suggests that the proposed method can achieve very fast reconstruction without compromising overall image quality and delineation of anatomical structures. MR parameter mapping is a promising approach to characterize intrinsic tissue-dependent information. To accelerate lengthy MR parameter mapping, which can take up to half an hour or more, a locally low-rank method has been proposed. The proposed method has been combined with parallel imaging to achieve further acceleration. Based on preliminary result, the combined parallel imaging locally low-rank method can accelerate variable flip angle T1 mapping by factor of 6, without obvious imaging artifacts. DCE MRI is a standard component of abdominal MRI exams, most commonly used to detect and characterize mass lesions and assess renal function. 3D DCE MRI is often limited compromised spatiotemporal resolution and motion artifacts. In this work, a combined locally low-rank parallel imaging method with soft gating is proposed. The proposed method can significantly reduce motion artifacts for completely free-breathing acquisition and remove the need for deep anesthesia. The high spatiotemporal resolution achieved by the proposed method can also capture the rapid contrast hemodynamics. The proposed method has been deployed clinically in Lucile Packard Children's Hospital at Stanford. Preliminary clinical evaluation results suggest that the proposed method can achieve an image quality very close to a respiratory-triggered data acquisition, but with much higher spatiotemporal resolution.
Author: James C. Carr
Publisher: Springer Science & Business Media
ISBN: 1441916857
Category : Medical
Languages : en
Pages : 416
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Book Description
Magnetic Resonance Angiography: Principles and Applications is a comprehensive text covering magnetic resonance angiography (MRA) in current clinical use. The first part of the book focuses on techniques, with chapters on contrast-enhanced MRA, time of flight, phase contrast, time-resolved angiography, and coronary MRA, as well as several chapters devoted to new non-contrast MRA techniques. Additionally, chapters describe in detail specific topics such as high-field MRA, susceptibility-weighted imaging, acceleration strategies such as parallel imaging, vessel wall imaging, targeted contrast agents, and low dose contrast-enhanced MRA. The second part of the book covers clinical applications of MRA, with each chapter describing the MRA techniques and protocols for a particular disease and vascular territory, as well as the pathology and imaging findings relevant to the disease state being discussed. Magnetic Resonance Angiography: Principles and Applications is designed to bring together into a single textbook all of the MRA techniques in clinical practice today and will be a valuable resource for practicing radiologists and other physicians involved in the diagnosis and treatment of vascular diseases, as well as biomedical physicists, MRI technologists, residents, and fellows. Editors James C. Carr, MD, is the Director of Cardiovascular Imaging and Associate Professor of Radiology and Medicine at Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA. Timothy J. Carroll, PhD, is the Director of MRI Research and Associate Professor in the Departments of Biomedical Engineering and Radiology at Northwestern University, Evanston, Illinois, USA. Magnetic Resonance Angiography: Principles and Applications is designed to bring together into a single textbook all of the MRA techniques in clinical practice today and will be a valuable resource for practicing radiologists and other physicians involved in the diagnosis and treatment of vascular diseases, as well as biomedical physicists, MRI technologists, residents, and fellows. Editors James C. Carr, MD, is Director of Cardiovascular Imaging and Associate Professor of Radiology and Medicine at Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA. Timothy J. Carroll, PhD, is Assistant Professor in the Department of Radiology at Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA. Editors James C. Carr, MD, is Director of Cardiovascular Imaging and Associate Professor of Radiology and Medicine at Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA. Timothy J. Carroll, PhD, is the Director of MRI Research and Associate Professor in the Departments of Biomedical Engineering and Radiology at Northwestern University, Evanston, Illinois, USA.
Author: Ali Ersoz
Publisher:
ISBN: 9780438707368
Category :
Languages : en
Pages : 121
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Book Description
Author: G. Schneider
Publisher: Springer Science & Business Media
ISBN: 8847003520
Category : Medical
Languages : en
Pages : 358
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Book Description
The advent of contrast-enhanced MRA in the early to mid 1990s revolutionized the clinical approach to vascular imaging: an accurate non-invasive imaging modality, not requiring ionizing radiation or potentially nephrotoxic iodinated contrast media, was able to compete with the more hazardous and invasive catheter angiography. Today, MRA is a safe, easy-to-perform procedure routinely used in most imaging centers, and the continued development of faster, more powerful magnets and more effective contrast agents is increasingly helping to overcome many of the early limitations of the technique. Subdivided into three sections (technique, indications and practical applications) and written by internationally renowned experts in the field, this volume stands out in the current literature on MRA by providing: - detailed information on sequence parameters for different magnets and vascular territories for the optimization of the MRA technique; - a broad overview of the principal indications for which contrast-enhanced MR angiography is ideally suited; - the typical MR imaging findings associated with various pathologies; - the appropriateness of contrast-enhanced MRA as compared with other modalities, such as CTA and CEUS; - the potential pitfalls and limitations of the technique in clinical routine. The volume will prove invaluable to radiologists and clinicians wishing to expand, improve, or consolidate their routine approach to vascular MR imaging.
Author: Volkert Brar Roeloffs
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
This thesis concentrates on methodological developments in both acquisition and reconstruction techniques when applying concepts from real-time imaging to the field of dynamic contrast-enhanced magnetic resonance imaging. In particular, a novel spoiling technique based on randomized radiofrequency phases is proposed to suppress undesired image artifacts. This technique allows fast, artifact-free acquisition of radially sampled T1 weighted data sets. The reconstruction of quantitative parameter maps from such data sets can be considered as a nonlinear inverse problem. In this work, a model-b...
Author: Andre J. Duerinckx
Publisher: Springer Science & Business Media
ISBN: 0387949593
Category : Medical
Languages : en
Pages : 355
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Book Description
In recent years, there has been increasing interest in the clinical applications of coronary angiography techniques. Coronary MRA can be instrumental in the evaluation of congenital coronary artery anomalies, however, the complexity of advanced MR pulse sequences and strategies may be overwhelming to many. Coronary MR Angiography demystifies the art of coronary MRA by providing a text in plain language with clearly illustrated imaging steps and protocols. Designed to bridge the gap between radiology and cardiology, it is written for physicians and scientists planning to incorporate this technique into their research or practice.
Author: Mehmet Akcakaya
Publisher: Academic Press
ISBN: 012822746X
Category : Science
Languages : en
Pages : 518
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Book Description
Magnetic Resonance Image Reconstruction: Theory, Methods and Applications presents the fundamental concepts of MR image reconstruction, including its formulation as an inverse problem, as well as the most common models and optimization methods for reconstructing MR images. The book discusses approaches for specific applications such as non-Cartesian imaging, under sampled reconstruction, motion correction, dynamic imaging and quantitative MRI. This unique resource is suitable for physicists, engineers, technologists and clinicians with an interest in medical image reconstruction and MRI. - Explains the underlying principles of MRI reconstruction, along with the latest research - Gives example codes for some of the methods presented - Includes updates on the latest developments, including compressed sensing, tensor-based reconstruction and machine learning based reconstruction
Author: Emanuele Neri
Publisher: Springer Science & Business Media
ISBN: 3540797173
Category : Medical
Languages : en
Pages : 178
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Book Description
Magnetic resonance angiography (MRA) continues to undergo exciting technological advances that are rapidly being translated into clinical practice. It also has evident advantages over other imaging modalities, including CT angiography and ultrasonography. With the aid of numerous high-quality illustrations, this book reviews the current role of MRA of the body. It is divided into three sections. The first section is devoted to issues relating to image acquisition technique and sequences, which are explored in depth. The second and principal section addresses the clinical applications of MRA in various parts of the body, including the neck vessels, the spine, the thoracic aorta and pulmonary vessels, the heart and coronary arteries, the abdominal aorta and renal arteries, and peripheral vessels. The final section considers the role of MRA in patients undergoing liver or pancreas and kidney transplantation. This book will be an invaluable aid to all radiologists who work with MRA.
