Download or read book Towards High resolution Magnetic Resonance Spectroscopic Imaging Spatiotemporal Denoising and Echo time Selection written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Spatial Resolution Magnetic Resonance Imaging and Magnetic Resonance Spectroscopic Imaging written by Susan Moyher Noworolski and published by . This book was released on 1999 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Clinically Relevant Magnetic Resonance Imaging and Spectroscopic Imaging Developmeht written by Sumi Bao and published by . This book was released on 1999 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Novel Applications of Compressed Sensing to Magnetic Resonance Imaging Spectroscopy written by Sairam Geethanath and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, three novel applications of compressed sensing to MRI have been developed and implemented which accomplish reduction in acquisition time, thereby also enabling increased spatial and/or temporal resolution. The first application is for reducing the acquisition time of conventional 1H magnetic resonance spectroscopic imaging (MRSI), which requires alongeracquisition time than conventional MRI. The implementation involved exploiting the inherent sparsity of the MRSI data in the wavelet domain by the use of Daubechies wavelet. This was demonstrated on an in vitro phantom, 6 healthy human brain MRSI data sets, 2 brain and prostate cancer data sets. The reconstructions were quantified by the use of the root-mean-square-error metric and subsequent statistical comparison of the metabolite intensities based on one-way ANOVA followed by Bonferroni's multiple comparison test. It was found that the implementation resulted in statistically significant differences at an acceleration of 10X and was considered the limit of the implementation. The implementation showed no significant differences until 5X. This indicates that CS has a potential to reduce conventional MRSI acquisition time by ̃80%. This reduction in time could be used to increase the spatial resolution of the scan or acquire harder-to-detect metabolites through increased averaging. Dynamic contrast enhanced MRI (DCE-MRI) is a MRI method that involves serial acquisition of images before and after the injection of a contrast agent. Therefore, it requires both high spatial and temporal resolution. The second application aims at accomplishing these requirements through the use of CS and comparing it with the widely-used method of key-hole imaging with respect to the choice of sampling masks and acceleration. Three sampling masks were designed for both approaches and reconstructions were performed at 2X, 3X, 4X and 5X. A semi-automatic segmentation procedure was followed to obtain regions of well and poorly perfused tissue and the results were compared using the RMSE metric and a voxel-wise paired t-test. The results of these tests showed that CS based masks performed better as compared to their key-hole counterparts and the sampling mask based on data thresholding performed the best. However, the exact implementation of this mask is impractical but an approximate solution was implemented for accelerating 3D gradient echo imaging. The third application that has been developed in this work relates to the acceleration of sweep imaging with Fourier transform (SWIFT) which is a novel MR method facilitating the visualization of short T2 species, which can yield important information about certain tissuessuch as cartilage. In this project, CS was applied to a resolution phantom and 5 human knee data sets acquired using SWIFT based imaging and accelerated up to 5X. The errors of reconstruction were quantified by RMSE and it was found that reconstructions at 5X maintained fidelity. A semi-automatic segmentation procedure was followed to segment the ligaments and adjoining structures and the number of segmented voxels was compared for the full data reconstruction and the accelerated cases. The 5X reconstruction showed a percentage difference of approximately 17% and was considered the limit of the implementation.

Download or read book Signal Processing for Magnetic Resonance Imaging and Spectroscopy written by Hong Yan and published by CRC Press. This book was released on 2002-02-20 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt: This reference/text contains the latest signal processing techniques in magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) for more efficient clinical diagnoses-providing ready-to-use algorithms for image segmentation and analysis, reconstruction and visualization, and removal of distortions and artifacts for increased detec

Download or read book Advanced Image Processing in Magnetic Resonance Imaging written by Luigi Landini and published by CRC Press. This book was released on 2018-10-03 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: The popularity of magnetic resonance (MR) imaging in medicine is no mystery: it is non-invasive, it produces high quality structural and functional image data, and it is very versatile and flexible. Research into MR technology is advancing at a blistering pace, and modern engineers must keep up with the latest developments. This is only possible with a firm grounding in the basic principles of MR, and Advanced Image Processing in Magnetic Resonance Imaging solidly integrates this foundational knowledge with the latest advances in the field. Beginning with the basics of signal and image generation and reconstruction, the book covers in detail the signal processing techniques and algorithms, filtering techniques for MR images, quantitative analysis including image registration and integration of EEG and MEG techniques with MR, and MR spectroscopy techniques. The final section of the book explores functional MRI (fMRI) in detail, discussing fundamentals and advanced exploratory data analysis, Bayesian inference, and nonlinear analysis. Many of the results presented in the book are derived from the contributors' own work, imparting highly practical experience through experimental and numerical methods. Contributed by international experts at the forefront of the field, Advanced Image Processing in Magnetic Resonance Imaging is an indispensable guide for anyone interested in further advancing the technology and capabilities of MR imaging.

Download or read book In Vivo NMR Spectroscopy written by Robin A. de Graaf and published by John Wiley & Sons. This book was released on 2019-03-11 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents basic concepts, experimental methodology and data acquisition, and processing standards of in vivo NMR spectroscopy This book covers, in detail, the technical and biophysical aspects of in vivo NMR techniques and includes novel developments in the field such as hyperpolarized NMR, dynamic 13C NMR, automated shimming, and parallel acquisitions. Most of the techniques are described from an educational point of view, yet it still retains the practical aspects appreciated by experimental NMR spectroscopists. In addition, each chapter concludes with a number of exercises designed to review, and often extend, the presented NMR principles and techniques. The third edition of In Vivo NMR Spectroscopy: Principles and Techniques has been updated to include experimental detail on the developing area of hyperpolarization; a description of the semi-LASER sequence, which is now a method of choice; updated chemical shift data, including the addition of 31P data; a troubleshooting section on common problems related to shimming, water suppression, and quantification; recent developments in data acquisition and processing standards; and MatLab scripts on the accompanying website for helping readers calculate radiofrequency pulses. Provide an educational explanation and overview of in vivo NMR, while maintaining the practical aspects appreciated by experimental NMR spectroscopists Features more experimental methodology than the previous edition End-of-chapter exercises that help drive home the principles and techniques and offer a more in-depth exploration of quantitative MR equations Designed to be used in conjunction with a teaching course on the subject In Vivo NMR Spectroscopy: Principles and Techniques, 3rd Edition is aimed at all those involved in fundamental and/or diagnostic in vivo NMR, ranging from people working in dedicated in vivo NMR institutes, to radiologists in hospitals, researchers in high-resolution NMR and MRI, and in areas such as neurology, physiology, chemistry, and medical biology.

Download or read book Principles of Magnetic Resonance Imaging written by Zhi-Pei Liang and published by Wiley-IEEE Press. This book was released on 2000 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1971 Dr. Paul C. Lauterbur pioneered spatial information encoding principles that made image formation possible by using magnetic resonance signals. Now Lauterbur, "father of the MRI", and Dr. Zhi-Pei Liang have co-authored the first engineering textbook on magnetic resonance imaging. This long-awaited, definitive text will help undergraduate and graduate students of biomedical engineering, biomedical imaging scientists, radiologists, and electrical engineers gain an in-depth understanding of MRI principles. The authors use a signal processing approach to describe the fundamentals of magnetic resonance imaging. You will find a clear and rigorous discussion of these carefully selected essential topics: Mathematical fundamentals Signal generation and detection principles Signal characteristics Signal localization principles Image reconstruction techniques Image contrast mechanisms Image resolution, noise, and artifacts Fast-scan imaging Constrained reconstruction Complete with a comprehensive set of examples and homework problems, Principles of Magnetic Resonance Imaging is the must-read book to improve your knowledge of this revolutionary technique.

Download or read book Optimal Observation Selection in Magnetic Resonance Spectroscopic Imaging written by Yun Gao and published by . This book was released on 2000 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Towards Absolutely Quantitative Phase Contrast Magnetic Resonance Imaging written by Matthew Joseph Middione and published by . This book was released on 2013 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase Contrast Magnetic Resonance Imaging (PC-MRI) is a non-invasive clinical imaging technique used primarily for measuring blood velocity and flow throughout the major blood vessels of the cardiovascular system. PC-MRI uses magnetic field gradients to impart zero phase to stationary spins and a non-zero phase to moving spins. The phase measurements provide quantitative information that is useful during the diagnosis and treatment of many cardiovascular diseases. Blood flow measurements obtained using PC-MRI hold an advantage over other techniques, namely echocardiography and catheterization, due to its ability to reduce lifetime radiation exposure, provide accurate and direct quantification of flow, and it's non-invasiveness. Despite decades of research, our ability to measure blood flow with PC-MRI is still hampered by quantitative inaccuracies leading to clinically significant errors, which dampens clinical enthusiasm for the technique. Nevertheless PC-MRI continues to be a compelling clinical technique because of the need to non-invasively measure flow in a wide range of clinical contexts. Frequently inconsistent PC-MRI measurements, however, continue to be a source of clinical frustration and in order for PC-MRI to become an absolutely quantitative measure of flow, both the accuracy and precision of these measurements must be improved. Herein an analysis of the effects of chemically shifted perivascular fat; time efficient velocity encoding; region-of-interest contouring; and the use of convex gradient optimization is conducted in an effort towards developing absolutely quantitative PC-MRI. In Chapter 4 we explore the phase errors associated with chemically shifted perivascular fat. Stationary perivascular fat, which surrounds most vessels throughout the cardiovascular system, can impart a significant chemical shift-induced phase error in PC-MRI. This chemical shift error does not subtract in phase difference processing, unlike other off-resonance phase errors, but can be minimized significantly with proper parameter selection. The chemical shift induced phase errors largely depend on both the receiver bandwidth and the echo time (TE). The amount of chemically shifted fat pixels that shift into the vessel can be reducedby increasing the receiver bandwidth while the use of an in-phase TE (TE_IN) will ensure that fat and water resonances are in-phase with slow flowing blood near the vessel wall, which minimizes the resulting errors in the calculated velocity. Computational simulations and both in vitro and in vivo experiments are used to show that the use of a high bandwidth and TE_IN significantly improves intra-subject flow agreement compared to a more clinically standard low receiver bandwidth and the minimum available TE (TE_MIN). In Chapter 5 we explore a time efficient chemical shift reduction strategy. The minimum available TE_IN at 3T field strength (TE_IN, MIN = 2.46ms), however, may not be routinely achievable with standard flow-encoding methods. Hence, we developed a novel method for flow encoding in PC-MRI, which uses the slice select gradientand a time-shifted refocusing gradient lobe for velocity encoding. Velocity encoding with the slice select refocusing gradient (SSRG) enables the use of TE_IN, MIN at 3T for time-efficient reduction of chemical shift-induced phase errors in PC-MRI, whereas this can't be achieved with bi-polar or flow compensated/flow encoded PC-MRI. In vivo measurements were acquired to show that PC-MRI measurements obtained using SSRG with a high receiver bandwidth and TE_IN, MIN significantly improves intra-subject flow agreement compared to a conventional clinical sequence, which uses a low receiver bandwidth and TE_MIN. This approach also increases temporal resolution and signal-to-noise ratio by 35% and 33%, respectively. In Chapter 6 we explore time efficient velocity encoding and the capabilities of convex gradient optimization in PC-MRI in chapter 7. Conventional PC-MRI pulse sequences use time inefficient velocity encoding methods along with trapezoidal and triangular gradient lobes, which do not make optimal use of the available gradient hardware. Convex gradient optimization (CVX) can be used to minimize PC-MRI gradient waveform durations subject to both gradient hardware and pulse sequence constraints. CVX PC-MRI with TE_IN, MIN provides more accurate measurements of blood flow and velocity through the reduction of chemical shift-induced phase errors and increased sequence efficiency, which can provide either higher spatial or higher temporal resolution. Another potential source of error in PC-MRI flow quantification occurs during image analysis. In Chapter 8 we analyze the errors associated with ROI contouring in PC-MRI. PC-MRI blood flowmeasurements require a region-of-interest (ROI) to be manually contoured to encompass the vessel lumen, but this process is subjective and prone to error. A systematic analysis of ROI contouring was used to evaluate the impact of overestimating and underestimating the ROI size on PC-MRI flow measurements. ROIs that overestimate the vessel lumen/wall boundary contribute a lower magnitude total flow error compared to ROIs that underestimate the same boundary. Reducing errors arising from chemically shifted perivascular fat, implementing time efficient velocity encoding, increasing spatiotemporal resolution through the use of convex gradient optimization, and careful analysis of ROI contours all help move us towards absolutely quantitative PC-MRI.

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 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 Spectroscopic Imaging Using Parallel Transmission at 7T written by Borjan Aleksandar Gagoski and published by . This book was released on 2011 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional magnetic resonance spectroscopic imaging (MRSI), also known as phase-encoded (PE) chemical shift imaging (CSI), suffers from both low signal-to-noise ratio (SNR) of the brain metabolites, as well as inflexible tradeoffs between acquisition time and spatial resolution. In addition, although CSI at higher main field strengths, e.g. 7 Tesla (T), offers improved SNR over clinical 1.5T or 3. OT scanners, the realization of these benefits is limited by severe inhomogeneities of the radio frequency (RF) excitation magnetic field (B, +), which is responsible for significant signal variation within the volume of interest (VOI) resulting in spatially dependent SNR losses. The work presented in this dissertation aims to provide the necessary means for using spectroscopic imaging for reliable and robust whole brain metabolite detection and quantification at high main field strengths. It addresses the challenges mentioned above by improving both the excitation and the readout components of the CSI acquisition. The long acquisition times of the PE CSI are significantly shortened (at least 20 fold) by implementing the time-efficient spiral CSI algorithm, while the B1 non-uniformities are corrected for using RF pulses designed for new RF excitation hardware at 7T, so-called parallel transmission (pTx). The B1 homogeneity of the pTx excitations improved at least by a factor of 4 (measured by the normalized spatial standard deviations) compared to conventional single channel transmit systems. The first contribution of this thesis describes the implementation of spiral CSI algorithm for online gradient waveform design and spectroscopic image reconstruction with standard clinical excitation protocols and applied in studies of Late-Onset Tay- Sachs (LOTS), adrenoleukodystrophy (ALD) and brain tumors. A major contribution of this thesis is pTx excitation design for CSI to provide spectral-spatial mitigation of the B1+ inhomogeneities at 7T. Novel pTx RF designs are proposed and demonstrated to yield excellent flip angle mitigation of the brain metabolites, and also enable improved suppression of the undesired water and lipid signals. A major obstacle to the deployment of 7T pTx applications for clinical imaging is the monitoring and management of local specific absorption rate (SAR). This thesis also proposes a pTx SAR monitoring system with real-time RF monitoring and shut-off capabilities.

Download or read book Radial Echo Planar Spectroscopic Imaging written by Andres Saucedo and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) are powerful, non-invasive tools that are capable of assessing the concentrations and distributions of various metabolic compounds in vivo. Single-voxel MRS methods such as STEAM and PRESS measure the temporal signal from a specific, localized volume of interest. As such, single-voxel MRS does not require any type of spatial encoding, such as frequency and phase encoding which are used routinely in magnetic resonance imaging (MRI). Although simpler to implement for clinical applications, MRS methods are nonetheless limited in their ability to efficiently acquire spectra across large anatomical regions, since only a relatively small volume can be probed per measurement. On the other hand, multi-voxel acquisitions can be done with MRSI, which incorporates additional two-dimensional (2D) or three-dimensional (3D) spatial encoding dimensions (i.e., k-space) to resolve multiple spectra from a large volume or slice within a single scan session. However, conventional MRSI techniques currently in clinical use depend on sequential phase encoding of each spatial dimension, which often results in long scan durations. Therefore, the focus of much research in MRSI has been to accelerate the acquisition through various means such as by undersampling or by using, often also in combination with undersampling, advanced sampling methods such as simultaneous spatiotemporal sampling of one spatial dimension and the spectral (time) dimension. The latter approach is accomplished by implementing so-called echo-planar k-t trajectories, which interleave the acquisition of one frequency-encoded spatial dimension (k) with the temporal samples (t) necessary for resolving the spectrum. The other spatial dimensions are often resolved with conventional phase encoding. Thus, echo-planar spectroscopic imaging (EPSI) is able to accelerate an MRSI scan session by at least an order of magnitude. When first proposed in the mid 1980's, EPSI was done with Cartesian trajectories and, since the late 1990's, non-Cartesian trajectories such as spirals, concentric circular, rosette, and radial trajectories have been implemented for fast MRSI. These non-Cartesian trajectories provide advantageous trade-offs in imaging speed, signal-to-noise ratio, and motion robustness compared with Cartesian EPSI. More recently, as late as 2019, radial echo planar spectroscopic imaging (REPSI) has been described as a nascent subfield in proton (1H) MRSI. Although radial projections were the first to be demonstrated for MRI, the adoption of radial sampling for MRSI had only found limited applications for non-proton MRSI, such as for phosphorus (31P) and carbon (13C), and had not yet been demonstrated for in vivo 1H MRSI. This work presents a study of 1H MRSI in the human brain in vivo using radial echo-planar trajectories, as well as applications for diffusion-weighted MRSI. The capability of REPSI for further acceleration compared to Cartesian EPSI are shown within a compressed sensing framework, in which the undersampled REPSI data can be reconstructed with good fidelity by exploiting the sparsity of the data within a transform domain. In addition to its higher tolerance for accelerations, the motion robustness of REPSI is shown in free-breathing healthy liver and prostate acquisitions. Both MRS and MRSI methods are compatible with diffusion-weighted (DW) techniques. DW-MRS and DW-MRSI are able to explore the microstructural characteristics of tissues in vivo due to the predominantly intracellular compartmentalization of metabolites. Unlike water, which permeates both the intra- and extra-cellular spaces, most metabolites are confined within the intracellular space, so that their diffusion reflects the structure and function of tissues at the microscopic scale. This compartment-specific assessment of tissue structure enables a clearer understanding of the cellular-level conditions and alterations that underlie various pathologies. This work also presents the first demonstration of a diffusion-weighted technique, first proposed in the mid 1990's and early 2000's, for in vivo single voxel DW-MRS and DW-MRSI in the human brain. This so-called "single-shot diffusion trace-weighted" scheme had been untestable in humans, until recently, due to earlier hardware limitations of clinical scanners. The acquisition and processing of the single voxel DW-MRS data was optimized as a precursor for the spectroscopic imaging version of the sequence. It is shown that radial echo planar trajectories are particularly advantageous for DW-MRSI, due to their self-navigation capability that enables post-processing-based corrections of the diffusion-weighted data, which is susceptible to shot-to-shot phase and frequency inconsistencies. In the Appendix, further work in acceleration in the context of parallel imaging using low-rank approximations is also demonstrated for MRI acquisitions.

Download or read book High speed Volumetric 1H Magnetic Resonance Spectroscopic Imaging written by Meng Gu and published by . This book was released on 2008 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Excitation and Readout Designs for High Field Spectroscopic Imaging written by Joonsung Lee and published by . This book was released on 2011 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we state and demonstrate solutions to three engineering problems that arise in magnetic resonance imaging RF excitation with parallel transmission (pTx) and magnetic resonance spectroscopic imaging (MRSI). Recent work in parallel RF excitation in MRI has been demonstrated to offer dramatically improved flexibility for manipulation of magnetization preparation for imaging than is feasible with conventional single-channel transmission. We address two design problems that need to be solved before this emerging technology can be deployed in the clinical and research domain of human imaging at high field. First, we demonstrate a method for rapid and robust acquisition of the non-uniform fields of RF excitation due to arrays that are commonly used in pTx at high field. Our method achieves high-fidelity single-slice excitation and reception field mapping in 20 seconds, and we propose ways to extend this to multi-slice mapping in two minutes for twenty slices. A fundamental constraint to the application of pTx is the management of the deposition of power in human tissue, quantified by the specific absorption rate (SAR). The complex behavior of the spatial distribution of SAR in transmission arrays poses problems not encountered in conventional single-channel systems, and we propose a pTx design method to incorporate local SAR constraints within computation times that accommodate pTx pulse design during MRI acquisition of human subjects. Our approach builds on recent work to capture local SAR distribution with much lower computational complexity than a brute-force evaluation, and we demonstrate that this approach can reduce peak local SAR by 20~40% for commonly applied pTx design targets. This thesis focuses on the design of excitation methods for high field system (7T parallel transmit (pTx) system) and fast readout and post-processing methods to reduce the lipid contamination to the brain. The contributions include fast B1+ mapping and pTx RF pulse design with the local SAR constraints for excitation. Regarding the readout method we developed a real time filter design, variable density spiral trajectory, and iterative non-linear reconstruction technique that reduce the lipid contamination. The proposed excitation methods were demonstrated using a 7T pTx system and the readout methods were implemented in a 3T system. Our third contribution addresses a recurring problem in MRSI of the brain, namely strong contaminating artifacts in low signal-to-noise ratio brain metabolite maps due to subcutaneous, high-concentration lipid sources. We demonstrate two methods to address this problems, one during the acquisition stage where a spatial filter is designed based on spatial priors acquired from the subject being scanned, and the second is a post-processing method that applies the brain and lipid source prior for further artifact minimization. These methods are demonstrated to achieve 20~4OdB enhancement of lipid suppression in brain MRSI of human subjects.

Download or read book High Spectral and Spatial Resolution Magnetic Resonance Imaging with Echo planar Acquisition written by Weiliang Du and published by . This book was released on 2003 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: