Chemical Exchange Saturation Transfer Imaging


Book Description

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.







Basics of Chemical Exchange Saturation Transfer (CEST) Magnetic Resonance Imaging


Book Description

Chemical exchange saturation transfer (CEST) is one of the contrast mechanisms in magnetic resonance imaging (MRI) and has been used to detect dilute proteins through the interaction between bulk water and labile solute protons. Amide proton transfer (APT) MRI has been developed for imaging diseases such as acute stroke. Moreover, various CEST agents have been explored to enhance the CEST effect. The contrast mechanism of CEST or APT MRI, however, is complex and depends not only on the concentration of amide protons or CEST agents and exchange properties, but also varies with imaging parameters such as radiofrequency (RF) power and magnetic field strength. When there are multiple exchangeable pools within a single CEST system, the contrast mechanism of CEST becomes even more complex. Numerical simulations are useful and effective for analyzing the complex contrast mechanism of CEST and for investigating the optimal imaging parameter values. In this chapter, we present the basics of CEST or APT MRI and a simple and fast numerical method for solving the time-dependent Bloch-McConnell equations for analyzing the behavior of magnetization and/or contrast mechanism in CEST or APT MRI. We also present a method for analyzing the behavior of magnetization in spin-locking CEST MRI.




SIMULTANEOUS ARTIFACTS CORRECTION AND ACCELERATION FOR CHEMICAL EXCHANGE SATURATION TRANSFER IMAGING VIA DEEP LEARNING


Book Description

Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) has emerged as a novel technology for precise diagnosis of various diseases using either endogenous molecules or exogenous administered contrast agents. CEST MRI methods rely on molecular signal saturation through radiofrequency pulses with the same frequency as a prescribed molecule (e.g., glutamate) to be measured in a magnetic field. Because the background signal from water modular is generally greater than the signal from the prescribed molecular by several orders of magnitude, there are many different types of molecules with similar magnetic frequency to be applied in CEST MRI. However, any offset from the desired frequency will produce large discrepancies due to the reduction of the background signal saturation. Current practice relies on acquiring extensive data at intentionally changed saturation frequencies and estimating the desired signal through data interpolation. This method is effective, but takes long acquisition time, making it impractical for clinical applications. To address this challenge, I developed CEST MRI methods to achieve the following two goals: 1) to accelerate the acquisition time; and 2) to increase the CEST contrast quantification quality. As the in-vivo MR environment is highly complicated and difficult to model accurately, I proposed to use deep learning (DL) to achieve these two goals. Three different methods are proposed to improve the procedure of CEST MRI: 1) a deep learning-based Glutamate CEST imaging B0-inhomogeneity correction method (DL-B0GluCEST) to accelerate the total scan time; 2) an improved DL-B0GluCEST method using data acquired from the downfield Z-spectrum only; 3) two deep learning-based methods for estimating B0 inhomogeneities from fewer calibration data. In contrast to currently practiced methods, my CEST methods are believing to be the first-of-its-kind CEST MRI methods utilizing deep learning approaches. More importantly, in my demonstrated applications, three proposed deep learning-based methods showed CEST contrast quantification quality improvement while significantly reducing CEST acquisition time by over 60%, 80%, and 80%, respectively.




MRI from Picture to Proton


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.




Contrast Agents for MRI


Book Description

As a practical reference guide for designing and performing experiments, this book focuses on the five most common classes of contrast agents for MRI namely gadolinium complexes, chemical exchange saturation transfer agents, iron oxide nanoparticles, manganese complexes and fluorine contrast agents. It describes how to characterize and evaluate them and for each class, a description of the theory behind their mechanisms is discussed briefly to orient the new reader. Detailed subchapters discuss the different physical chemistry methods used to characterize them in terms of their efficacy, safety and in vivo behavior. Important consideration is also given to the different physical properties that affect the performance of the contrast agents. The editors and contributors are at the forefront of research in the field of MRI contrast agents and this unique, cutting edge book is a timely addition to the literature in this area.




The Chemistry of Contrast Agents in Medical Magnetic Resonance Imaging


Book Description

Magnetic Resonance Imaging (MRI) is one of the most important tools in clinical diagnostics and biomedical research. The number of MRI scanners operating around the world is estimated to be approximately 20,000, and the development of contrast agents, currently used in about a third of the 50 million clinical MRI examinations performed every year, has largely contributed to this significant achievement. This completely revised and extended second edition: Includes new chapters on targeted, responsive, PARACEST and nanoparticle MRI contrast agents. Covers the basic chemistries, MR physics and the most important techniques used by chemists in the characterization of MRI agents from every angle from synthesis to safety considerations. Is written for all of those involved in the development and application of contrast agents in MRI. Presented in colour, it provides readers with true representation and easy interpretation of the images. A word from the Authors: Twelve years after the first edition published, we are convinced that the chemistry of MRI agents has a bright future. By assembling all important information on the design principles and functioning of magnetic resonance imaging probes, this book intends to be a useful tool for both experts and newcomers in the field. We hope that it helps inspire further work in order to create more efficient and specific imaging probes that will allow materializing the dream of seeing even deeper and better inside the living organisms. Reviews of the First Edition: "...attempts, for the first time, to review the whole spectrum of involved chemical disciplines in this technique..."—Journal of the American Chemical Society "...well balanced in its scope and attention to detail...a valuable addition to the library of MR scientists..."—NMR in Biomedicine




Methods for Chemical Exchange Saturation Transfer Magnetic Resonance Imaging


Book Description

Chemical exchange saturation transfer (CEST) is a relatively new magnetic resonance imaging (MRI) acquisition technique that generates contrast dependent on tissue microenvironment, such as protein concentration and intracellular pH. CEST imaging has the potential to become an important biomarker in a wide range of disorders. As an indicator of tissue pH, CEST imaging may allow the identification of the ischemic penumbra in stroke, and predict chemo- and radiation therapy outcomes in cancer. As a marker of protein concentration, CEST may be able to delineate tumor margins without contrast enhancement, identify disease onset in Alzheimer's disease, and monitor cartilage repair therapies. Despite several promising pilot studies, CEST imaging has had limited clinical application due to two main technical challenges. First, CEST imaging is extremely sensitive to magnetic field inhomogeneity. Images suffer from large susceptibility artifacts unless specialized BO inhomogeneity correction methods are employed that tremendously increase scan time. Second, the CEST contrast cannot be separated from the intrinsic macromolecular magnetization transfer (MT) asymmetry and brain images reflect the MT properties of white and gray matter rather than the desired protein and pH contrast. We have developed a novel CEST imaging acquisition scheme, dubbed saturation with frequency alternating RF irradiation (SAFARI), designed to be insensitive to Bo inhomogeneity and MT asymmetry. Studies in healthy volunteers demonstrate that SAFARI is robust in the presence of BO inhomogeneity and eliminates the need for specialized BO correction, thereby reducing scan time. In addition, results show that SAFARI removes the confounding MT asymmetry. We applied SAFARI imaging towards the study of the saturation transfer contrast in patients with high grade glioma. Results show that the contrast in brain tumors, which was previously attributed to an increase in the CEST signal from amide protons due to an elevated protein concentration, is instead the result of the loss of MT asymmetry found in the normal brain. Therefore, our work has lead to a new understanding of the different sources of signal in saturation transfer images of the brain with important implications for the design and analysis of future CEST studies of brain tumors.







Functional Neuroradiology


Book Description

Functional Neuroradiology: Principles and Clinical Applications, is a follow-up to Faro and Mohamed’s groundbreaking work, Functional (BOLD)MRI: Basic Principles and Clinical Applications. This new 49 chapter textbook is comprehensive and offers a complete introduction to the state-of-the-art functional imaging in Neuroradiology, including the physical principles and clinical applications of Diffusion, Perfusion, Permeability, MR spectroscopy, Positron Emission Tomography, BOLD fMRI and Diffusion Tensor Imaging. With chapters written by internationally distinguished neuroradiologists, neurologists, psychiatrists, cognitive neuroscientists, and physicists, Functional Neuroradiology is divided into 9 major sections, including: Physical principles of all key functional techniques, Lesion characterization using Diffusion, Perfusion, Permeability, MR spectroscopy, and Positron Emission Tomography, an overview of BOLD fMRI physical principles and key concepts, including scanning methodologies, experimental research design, data analysis, and functional connectivity, Eloquent Cortex and White matter localization using BOLD fMRI and Diffusion Tensor Imaging, Clinical applications of BOLD fMRI in Neurosurgery, Neurology, Psychiatry, Neuropsychology, and Neuropharmacology, Multi-modality functional Neuroradiology, Beyond Proton Imaging, Functional spine and CSF imaging, a full-color Neuroanatomical Brain atlas of eloquent cortex and key white matter tracts and BOLD fMRI paradigms. By offering readers a complete overview of functional imaging modalities and techniques currently used in patient diagnosis and management, as well as emerging technology, Functional Neuroradiology is a vital information source for physicians and cognitive neuroscientists involved in daily practice and research.