Download or read book M1 Space Under Sampling Fast Phase Contrast Magnetic Resonance Imaging written by Da Wang and published by . This book was released on 2017 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase Contrast Magnetic Resonance Imaging (PC-MRI) is one of the primary means for quantification of blood flow and velocity. In conventional PC-MRI, the Flow Compensated (FC) and the three-directional (3D) Flow Encoded (FE) images are acquired in an interleaved fashion, and each directional blood flow velocity is encoded in the phase difference between each directional FE and the FC data. This acquisition strategy often limits its achievable temporal sampling period and temporal footprint. Temporal sampling period and temporal footprint are two important indices govern the measurement accuracy of the maximum peak velocity. The underestimation of the maximum peak velocity due to long temporal sampling period and long temporal footprint may result in misdiagnosis of a number of clinical diseases, such as artery stenosis. In the conventional 4D flow PC-MRI, each cardiac phase requires four acquisitions (i.e. one FC and 3D FE, FC/3FE) to update the 3D velocity vector field. Thus, the temporal sampling period and temporal footprint of 4D flow PC-MRI equal to 4*TR*Views-per-segment. Using a small views-per-segment (VPS) can achieve a decreased temporal sampling period and temporal footprint but concomitantly increase the total scan time. So far, fast PC-MRI techniques are majorly implemented to compensate the increase of the total acquisition time. In this work, we first introduce the gradient first moment (M1) space under-sampling, which aims to reduce the number of the four samples (FC and 3D FE) required for 4D flow reconstruction. This is the unique advantage of M1-space under-sampling over conventional fast PC-MRI techniques. It can improve both the temporal sampling period and temporal footprint without increasing the total scan time or reduce the total scan time with fixed temporal sampling period and temporal footprint. Furthermore, the M1-space is a novel dimension to accelerate 4D flow scans, so it can be combined with K-space, K-t-space, temporal dimension fast PC-MRI techniques to achieve further acceleration. In Chapter 2, we propose a technique to use sliding window temporal view sharing of the FC data (FCVS) to accelerate PC-MRI. The technique aims to accelerate certain PC-MRI applications, such as assessment of volumetric blood flow in the carotid arteries, intracranial vessels and peripheral vessels, where the physiological motion is minor and the FC background phase is not expected to change significantly over time. In this regard, the conventional PC-MRI acquisition strategy is redundant since it repetitively acquires the similar FC data for each cardiac phase. Especially the FC data does not contain dynamic flow velocity information. The FCVS technique achieves two-fold acceleration compared to standard through-plane encoding (FC/FE) PC-MRI. More importantly, the FCVS approach improves both the temporal sampling period and temporal footprint, which are very important for accurate velocity and flow quantification. Computational simulations and both retrospective and prospective in vivo studies demonstrated that the FCVS technique provides more accurate maximum peak velocity measurement while maintaining the measurement accuracy of total volumetric flow compared with conventional FCFE technique. In Chapter 3, we propose a 4D flow PC-MRI strategy, which is completely free of FC data acquisition and achieves 4/3-fold acceleration. In this technique, we hypothesize that the velocity direction (not magnitude) remains relatively unchanged within two cardiac phases (~100-150ms) during the cardiac cycle. The velocity direction consistency constraint enables the FC background phase calculation based on 3D FE data. Thus, the four M1-space samples (FC/3FE) have been reduced to three samples (3FE). The HOTFEO achieves 4/3-fold acceleration. However, the velocity direction consistency constraint has two ill conditions: the two consecutive velocities equal to each other and they are along the diagonal direction in the logical encoding coordinate. To address these problems, we propose to use a hybrid one- and two-sided flow encoding only (HOTFEO) strategy. More specifically, that is to use FE acquisition pattern with alternating polarity (i.e. two-sided FE) in the Y-direction (FEy) in addition to using single polarity (i.e. one-sided) FEx and FEz. The HOTFEO pattern can address the two ill conditions by converting the underdetermined constraint into convex function optimizations. The HOTFEO technique can also significantly increase the accuracy of FC background calculation and result in more accurate maximum peak velocity and total volumetric flow measurement. In Chapter 4, we propose a two-fold accelerated 4D flow PC-MRI technique with hybrid one- and two-sided flow encoding and velocity spectrum separation (HOTSPA). There are three components in the HOTSPA technique: 1) the two-sided FE has been applied in two of the three FE directions; 2) the one-sided FE has been applied in the remaining FE direction; 3) the FC data is not explicitly acquired. The two-sided FE strategy provides a 0/ linear phase modulation in the temporal dimension. In the Fourier velocity spectrum domain, the spectrum of temporal modulated velocity waveform will be shifted by half of the frequency support and separated from the spectrum of FC or one-sided FE waveform. The HOTSPA technique then separates the Fourier velocity spectra into components for FC background phase and 3D velocity waveforms. The combinations of the acquired data enable 3D velocity calculations based on two M1-space samples instead of four samples as conventional 4D flow PC-MRI. The HOTSPA technique can be used to either improve the temporal sampling period and temporal footprint or reduce the total scan time. The approach has been demonstrated to provide more accurate maximum peak velocity and total volumetric flow measurements. The M1-space under-sampling is a novel and promising technique to accelerate PC-MRI. First, it can improve both temporal sampling period and temporal footprint by reducing the M1-space samples. Second, it can accelerate 4D flow independently or it can be applied on phase images after finishing other fast PC-MRI technique reconstructions, such as compressed sensing, parallel imaging, non-Cartesian trajectory, thus allowing their combination to achieve further acceleration. In Chapter 4, we will introduce the balanced four-point flow encoding strategy, which can achieve four-fold acceleration using HOTSPA technique. The M1-space under-sampling can significantly improve the measurement accuracy of velocity and flow quantifications or reduce the total scan time, especially for 4D flow applications.

Download or read book Simulation of BRISK and FAST Phase contrast Magnetic Resonance Imaging by Computational Fluid Dynamics written by Bradley L. Hershey and published by . This book was released on 2003 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rapid Phase contrast Magnetic Resonance Imaging Using Spiral Trajectories and Parallel Imaging written by Jennifer Anne Steeden and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Magnetic Resonance Imaging written by Marinus T. Vlaardingerbroek and published by Springer Science & Business Media. This book was released on 2003 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents an overall analytical treatment of MRI physics and engineering. Special attention is paid to the treatment of intrinsic artefacts of the different sequences which can be described for the different scan methods. The book contains many images, especially showing specific properties of the different scan methods. The methods discussed include RARE, GRASE, EPI and Spiral Scan. The 3rd edition deals with stranger gradient and new RF coil systems, and sequences such as Balanced FFE and q-space diffusion imaging and SENSE.

Download or read book Fundamentals of Magnetic Resonance Imaging written by Jintong Mao and published by Independently Published. This book was released on 2019-10-25 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is in black and white printing. It was revised on 05/30/2020. Starting from complex free induction decay (FID), this book establishes a logical framework for the discussion of the principles of MRI. Based on the framework, traditional topics and some new topics are described in detail. Every formula is derived step by step at length. Essence of MRI is thoroughly discussed. It is emphasized that Fourier transform (FT) in MRI is a natural result from data acquisition if with a linear field gradient. Each concept, particularly the concept of echo, is explained in detail. For example, it is indicated that the popular drawing of an echo following a single FID (note this "single") in time axis is misleading in MRI (but may not in NMR). An echo cannot be considered as two back to back FID, etc. If you cannot accept these statements immediately, you may need to refresh your basic knowledge of MRI. The procedure from FID to MR image is accomplished by a pair of FT. The first FT is established naturally and automatically from echo acquisition. Analog digital converter leads to discrete FID. Using Nyquist sampling and quadrature phase sensitive detection (PSD), formula FOV*dk = 2pi is derived. From FOV*dk=2pi, discrete FT is derived by the summation of discrete FID directly, without relying on continuous FT. Thus, discrete FID leads to discrete FT. On other side, a discrete echo is the summation of acquired discrete FID, if re-phasing linear gradient field follows de-phasing gradient field. Thus, discrete FID also leads to discrete echo. We have the result that the discrete echo is a discrete FT (one dimensional). A series of echoes is obtained by phase encoding (raw data in two-dimensional k-space). The k-space, therefore, is a two-dimensional discrete FT (first FT). The reconstructed image is obtained by applying inverse FT (second FT) to the series of discrete echoes (k-space). Continuous FT is used as a heuristic step. But it is not necessary for the discussion of MRI. As example from FID to MR image, simulated images are obtained for graphical phantoms by using MATLAB. In appendix, MATLAB codes for image reconstruction and for some frequency selective pulses are included. Based on the framework, the topics include basic pulse sequences; pulse train; image contrasts; signal to noise ratio; ringing artifacts; aliasing artifacts; improvement of slice profile of selective pulses (Bloch equation is solved numerically using Runge-Kutta method); fat suppression; magnetization transfer; diffusion; flow image; functional MRI (fMRI for a perceptual alternation is presented), etc. Inside of the framework, emphasized topics include pulsatile ghost artifact for flow that is simulated by MATLAB and explained by interleaved zero data in k-space; experiments show that traditional explanation of flow mis-registration is not correct; the experiment also shows that the profile of laminar flow looks like a long needle, instead of ellipsoid; Stejskal-Tanner formula for b-value can be obtained by a wrong derivation, thus, the correctness of the formula may be in question; the strength of refocusing gradient for 90d selective pulse is-0.515, instead of commonly used -0.5 (small difference in refocusing strength leads to a large difference in refocusing effects due to non-linearity of Bloch equation); etc. In addition to above topics, Bloch equation with the terms T1, T2, diffusion, flow, etc. is derived by adding independent contributions to dM/dt with the assumption that T2 functions only in x-y plane. It is the hope this book is readable. It is the hope that the journey through the book might be a joy. This book will be of value to beginners. Perhaps it is valuable to a more extensive readership as well.

Download or read book Low discrepancy K space Sampling Strategies for Magnetic Resonance Imaging written by Tobias Speidel and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Functional Magnetic Resonance Imaging at High Spatiotemporal Resolution Using EPI Combined with Different K Space Undersampling Techniques at 3 Tesla written by Sebastian Domsch and published by . This book was released on 2013 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantitative Magnetic Resonance Imaging written by Nicole Seiberlich and published by Academic Press. This book was released on 2020-11-18 with total page 1094 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantitative Magnetic Resonance Imaging is a ‘go-to’ reference for methods and applications of quantitative magnetic resonance imaging, with specific sections on Relaxometry, Perfusion, and Diffusion. Each section will start with an explanation of the basic techniques for mapping the tissue property in question, including a description of the challenges that arise when using these basic approaches. For properties which can be measured in multiple ways, each of these basic methods will be described in separate chapters. Following the basics, a chapter in each section presents more advanced and recently proposed techniques for quantitative tissue property mapping, with a concluding chapter on clinical applications. The reader will learn: The basic physics behind tissue property mapping How to implement basic pulse sequences for the quantitative measurement of tissue properties The strengths and limitations to the basic and more rapid methods for mapping the magnetic relaxation properties T1, T2, and T2* The pros and cons for different approaches to mapping perfusion The methods of Diffusion-weighted imaging and how this approach can be used to generate diffusion tensor maps and more complex representations of diffusion How flow, magneto-electric tissue property, fat fraction, exchange, elastography, and temperature mapping are performed How fast imaging approaches including parallel imaging, compressed sensing, and Magnetic Resonance Fingerprinting can be used to accelerate or improve tissue property mapping schemes How tissue property mapping is used clinically in different organs Structured to cater for MRI researchers and graduate students with a wide variety of backgrounds Explains basic methods for quantitatively measuring tissue properties with MRI - including T1, T2, perfusion, diffusion, fat and iron fraction, elastography, flow, susceptibility - enabling the implementation of pulse sequences to perform measurements Shows the limitations of the techniques and explains the challenges to the clinical adoption of these traditional methods, presenting the latest research in rapid quantitative imaging which has the possibility to tackle these challenges Each section contains a chapter explaining the basics of novel ideas for quantitative mapping, such as compressed sensing and Magnetic Resonance Fingerprinting-based approaches

Download or read book Nonuniform and Non Cartesian Sampling in Multidimensional Magnetic Resonance Spectroscopic Imaging written by Neil Wilson and published by . This book was released on 2015 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance spectroscopy (MRS) is used to obtain localized biochemical information noninvasively based on the principles of nuclear magnetic resonance. 1H in vivo spectra consist of a large number of metabolites in a relatively small spectral range, making identification difficult. Multidimensional MRS incorporates a variable evolution period to enhance the information content and increase spectral dispersion. Recently, multidimensional MRS has been combined with echo planar gradient readout techniques to produce multidimensional magnetic resonance spectroscopic imaging (MRSI). Despite the fast imaging acquisitions, these scans are long for in vivo studies, so more efficiently sampling strategies were investigated. The first strategy consisted of nonuniform undersampling (NUS) of the volume spanned by the phase-encoded spatial dimensions and the indirect spectral dimension in 5 dimensional (3 spatial + 2 spectral) MRSI. Nonlinear reconstruction was performed according to the theory of compressed sensing (CS) using the split Bregman framework. Formulations that promoted sparsity of the data and its spatial finite differences in 5D J-resolved brain studies were applied, and results were compared favorably to a time-equivalent single slice J-resolved scan. In 5D correlated MRSI calf studies, reconstruction minimized the group sparsity of nearby points, which produced much better results than reconstruction that minimized the overall sparsity of the data. The second strategy used concentrically circular k-space trajectories instead of the conventional rectilinear ones. Concentric circles have the advantages of reduced hardware demands, higher achievable spectral bandwidth, less sensitivity to motion, and faster k-space coverage. Single slice 4D (2 spatial + 2 spectral) correlated MRSI using concentrically circular trajectories was compared to a rectilinear counterpart and showed similar data quality. An improved single slice J-resolved MRSI sequence was presented. The new sequence used adiabatic refocusing pulses that are less sensitive to RF field inhomogeneity and result in reduced chemical shift displacement error compared to conventional pulses. Comparison was made to the nonadiabatic sequence with the same echo time as well as with its minimum echo time.

Download or read book Magnetic Resonance Elastography written by Sudhakar K. Venkatesh and published by Springer. This book was released on 2014-10-01 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first book to cover the groundbreaking development and clinical applications of Magnetic Resonance Elastography, this book is essential for all practitioners interested in this revolutionary diagnostic modality. The book is divided into three sections. The first covers the history of MRE. The second covers technique and clinical applications of MRE in the liver with respect to fibrosis, liver masses, and other diseases. Case descriptions are presented to give the reader a hands-on approach. The final section presents the techniques, sequence and preliminary results of applications in other areas of the body including muscle, brain, lung, heart, and breast.

Download or read book Magnetic Resonance Imaging written by Robert W. Brown and published by John Wiley & Sons. This book was released on 2014-06-23 with total page 976 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book The Physics and Mathematics of MRI written by Richard Ansorge and published by Morgan & Claypool Publishers. This book was released on 2016-11-01 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Resonance Imaging is a very important clinical imaging tool. It combines different fields of physics and engineering in a uniquely complex way. MRI is also surprisingly versatile, 'pulse sequences' can be designed to yield many different types of contrast. This versatility is unique to MRI. This short book gives both an in depth account of the methods used for the operation and construction of modern MRI systems and also the principles of sequence design and many examples of applications. An important additional feature of this book is the detailed discussion of the mathematical principles used in building optimal MRI systems and for sequence design. The mathematical discussion is very suitable for undergraduates attending medical physics courses. It is also more complete than usually found in alternative books for physical scientists or more clinically orientated works.

Download or read book Medical Imaging Systems written by Andreas Maier and published by Springer. This book was released on 2018-08-02 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book gives a complete and comprehensive introduction to the fields of medical imaging systems, as designed for a broad range of applications. The authors of the book first explain the foundations of system theory and image processing, before highlighting several modalities in a dedicated chapter. The initial focus is on modalities that are closely related to traditional camera systems such as endoscopy and microscopy. This is followed by more complex image formation processes: magnetic resonance imaging, X-ray projection imaging, computed tomography, X-ray phase-contrast imaging, nuclear imaging, ultrasound, and optical coherence tomography.

Download or read book MRI from Picture to Proton written by Donald W. McRobbie and published by Cambridge University Press. This book was released on 2017-04-13 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Magnetic Resonance Imaging and Spectroscopy written by Fred A. Mettler and published by . This book was released on 1986 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heart Mechanics written by El-Sayed H. Ibrahim and published by CRC Press. This book was released on 2017-09-19 with total page 740 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on research and clinical trials, this book details the latest research in magnetic resonance imaging (MRI) tagging technology related to heart mechanics. It covers clinical applications and examines future trends, providing a guide for future uses of MRI technology for studying heart mechanics.

Download or read book Chemical Exchange Saturation Transfer Imaging written by Michael T. McMahon and published by CRC Press. This book was released on 2017-01-12 with total page 463 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first textbook dedicated to CEST imaging and covers the fundamental principles of saturation transfer, key features of CEST agents that enable the production of imaging contrast, and practical aspects of preparing image-acquisition and post-processing schemes suited for in vivo applications. CEST is a powerful MRI contrast mechanism with unique features, and the rapid expansion it has seen over the past 15 years since its original discovery in 2000 has created a need for a graduate-level handbook describing all aspects of pre-clinical, translational, and clinical CEST imaging. The book provides an illustrated historical perspective by leaders at the five key sites who developed CEST imaging, from the initial saturation transfer NMR experiments performed in the 1960s in Stockholm, Sweden, described by Sture Forsén, to the work on integrating the basic principles of CEST into imaging by Robert Balaban, Dean Sherry, Silvio Aime, and Peter van Zijl in the United States and Italy. The editors, Drs. Michael T. McMahon, Assaf A. Gilad, Jeff W. M. Bulte, and Peter C. M. van Zijl, have been pioneers developing this field at the Johns Hopkins University School of Medicine and the Kennedy Krieger Institute including contributions to Nature Medicine, Nature Biotechnology, Nature Materials, and the Proceedings of the National Academy of Sciences. As recognition for their initial development of the field, Drs. van Zijl and Balaban were awarded the Laukien Prize in April 2016, established in 1999 to honor the memory of Professor Gunther Laukien, a co-founder of Bruker Biospin GmbH.