Development and Validation of Novel Quantitative MRI Techniques in Liver


Book Description

MRI methods to evaluate diffuse hepatic diseases have advanced substantially in recent years, with a particular focus on chemical shift encoded (CSE)-MRI. However, the systematic evaluation of these methods requires the development of highly controlled quantitative imaging test objects ("phantoms"). In addition, CSE-MRI methods face major limitations, particularly their high sensitivity to physiological motion, and challenges in measuring parameters such as magnetic susceptibility (an emerging biomarker for tissue iron deposition). In this thesis, technical developments are introduced to address these challenges in both quantitative imaging phantoms and quantitative liver MRI methods. Novel quantitative MRI phantoms were designed and developed to mimic the simultaneous presence of fat, iron, and fibrosis in the liver by controlling different MR biomarkers while mimicking in vivo liver signals. An MRI and CT compatible fat phantom was developed and evaluated in a round-robin multi-center multi-vendor study. Motion-robust free breathing 2D sequential CSE-MRI method with flip angle modulation (FAM) and centric encoding approach was developed to achieve high SNR performance and minimal T1 bias simultaneously for liver fat and iron quantification. To further boost SNR performance, motion-corrected averaging method was combined with FAM CSE-MRI. Finally, a recently proposed liver quantitative susceptibility mapping (QSM) method was evaluated across iron levels and acquisition protocols at 1.5T and 3.0T, using superconducting quantum interference device (SQUID) liver susceptometry as the reference. Overall, these developments in this thesis have advanced MRI of the liver towards becoming a truly quantitative imaging modality.




Development and Validation of Novel Quantitative MRI Techniques in Liver


Book Description

MRI methods to evaluate diffuse hepatic diseases have advanced substantially in recent years, with a particular focus on chemical shift encoded (CSE)-MRI. However, the systematic evaluation of these methods requires the development of highly controlled quantitative imaging test objects ("phantoms"). In addition, CSE-MRI methods face major limitations, particularly their high sensitivity to physiological motion, and challenges in measuring parameters such as magnetic susceptibility (an emerging biomarker for tissue iron deposition). In this thesis, technical developments are introduced to address these challenges in both quantitative imaging phantoms and quantitative liver MRI methods. Novel quantitative MRI phantoms were designed and developed to mimic the simultaneous presence of fat, iron, and fibrosis in the liver by controlling different MR biomarkers while mimicking in vivo liver signals. An MRI and CT compatible fat phantom was developed and evaluated in a round-robin multi-center multi-vendor study. Motion-robust free breathing 2D sequential CSE-MRI method with flip angle modulation (FAM) and centric encoding approach was developed to achieve high SNR performance and minimal T1 bias simultaneously for liver fat and iron quantification. To further boost SNR performance, motion-corrected averaging method was combined with FAM CSE-MRI. Finally, a recently proposed liver quantitative susceptibility mapping (QSM) method was evaluated across iron levels and acquisition protocols at 1.5T and 3.0T, using superconducting quantum interference device (SQUID) liver susceptometry as the reference. Overall, these developments in this thesis have advanced MRI of the liver towards becoming a truly quantitative imaging modality.







Quantitative Magnetic Resonance Imaging Biomarkers for Diffuse Liver Disease: Technical Development and Validation


Book Description

Non-alcoholic fatty liver disease (NAFLD) is a common liver disorder hallmarked by abnormal deposition of fat, i.e.: hepatic steatosis. NAFLD can take the form of non-alcoholic steatohepatitis (NASH) or isolated steatosis. Both forms of NAFLD can cause chronic liver injuries which leads to the progression into liver fibrosis. At the same time, NAFLD is a known risk factor of type-II diabetes and premature cardiovascular diseases. Although liver fibrosis is less common than NAFLD, it has serious complications such as liver failure. Cirrhosis as a form of advanced fibrosis is a risk factor of hepatocellular carcinoma. Effective treatments are emerging for NAFLD and liver fibrosis. Lifestyle intervention has been demonstrated to reduce hepatic steatosis and inflammation. In the case of viral hepatitis, treatment for hepatitis C virus infection often leads to the reversal of liver fibrosis (even in patients with cirrhosis). The accurate evaluation of hepatic steatosis and fibrosis using non-invasive magnetic resonance imaging (MRI) methods are needed to improve the diagnosis and treatment monitoring of patients afflicted by these conditions. Chemical shift encoded (CSE)-MRI has been established as a quantitative imaging biomarker (QIB) for hepatic steatosis. In this dissertation, the effect of non-standardized spectral model of fat was evaluated such that meaningful comparisons can be made between results obtained at different research and clinical sites. A T[subscript 1]-corrected variable flip angle (VFA) CSE-MRI was also proposed and rigorously evaluated for fat quantification in the hope of improving the precision of CSE-MRI fat quantification. Quantitative diffusion MRI using an intra-voxel incoherent motion (IVIM) model and T[subscript 2] mapping have shown promise for the evaluation of liver fibrosis. However, some additional development and validation is required for them to be recognized as QIBs. In this dissertation, a novel acetone-based diffusion phantom was proposed to provide a controlled environment for the development of quantitative diffusion MRI techniques. Further, to enable the quantification of T[subscript 2] from the water signal (parenchyma) and simultaneous quantification of R[subscript 2]*, a novel phase-based T[subscript 2] mapping technique was developed with its feasibility in the liver demonstrated.




Quantitative Magnetic Resonance Imaging


Book Description

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




Magnetic Resonance Elastography


Book Description

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.




Master Techniques in Surgery: Hepatobiliary and Pancreatic Surgery


Book Description

Hepatobiliary and Pancreatic Surgery is part of the Master Techniques in Surgery Series, which presents common and advanced procedures in the major subspecialties of general surgery. The series is overseen by Josef E. Fischer, MD, editor of the classic two-volume reference Mastery of Surgery. Hepatobiliary and Pancreatic Surgery depicts surgery of the liver, hepatobiliary tree, and pancreas, including cholecystectomy and hepatic resections. Both laparoscopic and open procedures are depicted. The book is written by acknowledged master surgeons, emphasizes surgical procedures, and is lavishly illustrated with original full-color drawings. Each chapter briefly assesses indications, contraindications, and preoperative planning before fully explaining and illustrating the procedure in step-by-step detail. Outcomes, complications, and follow-up are also discussed. Each chapter ends with a brief reference list. A companion website will offer the fully searchable content of the book and procedural videos.




Diseases of the Abdomen and Pelvis 2018-2021


Book Description

This open access book deals with imaging of the abdomen and pelvis, an area that has seen considerable advances over the past several years, driven by clinical as well as technological developments. The respective chapters, written by internationally respected experts in their fields, focus on imaging diagnosis and interventional therapies in abdominal and pelvic disease; they cover all relevant imaging modalities, including magnetic resonance imaging, computed tomography, and positron emission tomography. As such, the book offers a comprehensive review of the state of the art in imaging of the abdomen and pelvis. It will be of interest to general radiologists, radiology residents, interventional radiologists, and clinicians from other specialties who want to update their knowledge in this area.




PET/MRI


Book Description

In compiling this textbook on the exciting novel imaging modality of PET/MRI, the editors have brought together a truly international group of experts in the field. The book is divided into two parts. The first part covers methodology and equipment and includes chapters on basic molecular medicine, contrast agents, MR attenuation and validation, and quantitative MRI and PET motion correction. The second part of the book focuses on clinical applications in oncology, cardiology, and neurology. Imaging of major neoplasms is covered in a series of individual chapters. Further chapters address functional and metabolic cardiovascular examinations and major central nervous system applications such as brain tumors and dementias. This book will be of interest to all radiologists and nuclear medicine physicians who wish to learn more about the latest developments in this important emerging imaging modality and its applications.




Clinical Perfusion MRI


Book Description

This concise and comprehensive review uniquely contains all the information required to perform and interpret clinical MR perfusion imaging.