Contents
Preface
CHAPTER ONE PHYSICS
Diagnostic Radiology
Nuclear Medicine or Gamma Scintigraphy
Computed Tomography
Ultrasonography
Magnetic Resonance Imaging
T2 Sequence
T1 Sequence
STIR Sequence
FLAIR Sequence
Gradient Echo Sequence
Hardware Artifacts
Phase and Frequency Artifacts
Chemical Shift Artifact
Fold-Over or Aliasing Artifact
Truncation Artifact
Magnetic Susceptibility Artifact
Volume Averaging Artifact
Magic Angle Artifact
Cross-Talk Artifact
Safety
CHAPTER TWO VETERINARY CLINICAL MAGNETIC RESONANCE IMAGING
Neuroanatomical Considerations
Supratentorial Nervous System
Infratentorial Nervous System
Individual Cranial Nerves
Non-Neural Intracranial Elements
Important and Definable Landmarks
Diagnosis of Pathophysiological Conditions of the Intracranial Nervous System
Cerebral Edema
Intracranial Vascular Disease
Seizures
Ventricular Obstruction (Also See Section “Hydrocephalus” In This Chapter)
Increases in Intracranial Pressure
Terminal Effects of Compartmentalized ICP Increases—Brain Herniation
Diagnosis of Specific Intracranial Diseases
Intracranial imaging artifacts
Bibliography
Anatomy
General Types of Spinal Cord Pathophysiology
Diagnosis of Spinal Cord Disease Processes
MR Bibliography
Anatomical Considerations
Specific Diseases
MR Bibliography
CHAPTER THREE ORTHOPEDIC
Imaging Technique
Brachial Plexus Disease
Pelvic Region
Nerve Sheath Tumors
Stifle Joint
Tarsus and Carpus Regions
Bibliography
CHAPTER FOUR MAGNETIC RESONANCE IMAGING OF ABDOMINAL DISEASE
Normal Abdominal Anatomy
Abnormalities of the Liver and associated structures
Abnormalities of the kidneys and adrenal glands
Other Associated Organs
Portosystemic Shunts
Other vascular abnormalities
Bibliography
CHAPTER FIVE THORAX
Anatomy
Imaging Procedure
Cardiac
Mediastinal
Pulmonary
Bibliography
CHAPTER SIX HEAD—NON-CNS
Anatomy
Imaging Procedure
Nasal Cavity
Oral Cavity
External, Middle, and Inner Ear
Orbit Conditions
Other
Conclusion
Bibliography
CHAPTER SEVEN CANCER IMAGING
Introduction
Technical Considerations for Cancer MR
Whole Body MR for Cancer Staging
MR Imaging Techniques for Radiation Therapy Planning
Imaging Residual Tumor and Tumor Recurrence
Physiological and Molecular Imaging With MR
Specific Areas
Conclusion
Acknowledgments
Bibliography
Color plates
Index
Edition first published 2009
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Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought.
Library of Congress Cataloging-in-Publication Data
Gavin, Patrick R.
Practical small animal MRI/Patrick R. Gavin, Rodney S. Bagley.
p.; cm.
Includes bibliographical references and index.
ISBN-13: 978-0-8138-0607-5 (alk. paper)
ISBN-10: 0-8138-0607-0 (alk. paper)
1. Veterinary radiography. 2. Magnetic resonance imaging. I. Bagley, Rodney S. II. Title.
[DNLM: 1. Magnetic Resonance Imaging–veterinary. SF 757.8 G283p 2009]
SF757.8G38 2009
636.089’607548–dc22
2008040608
Disclaimer
The contents of this work are intended to further general scientific research, understanding, and discussion only and are not intended and should not be relied upon as recommending or promoting a specific method, diagnosis, or treatment by practitioners for any particular patient. The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of fitness for a particular purpose. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. Readers should consult with a specialist where appropriate. The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization orWebsite may provide or recommendations it may make. Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read. No warranty may be created or extended by any promotional statements for this work. Neither the publisher nor the author shall be liable for any damages arising herefrom.
DEDICATION
This work is dedicated to our former and current radiology and neurology residents, the animal patients, and their owners.
Rod Bagley
Pat Gavin
PREFACE
Dr. Rod Bagley and I discussed writing a textbook on Veterinary MRI for several years. Rod had already published a textbook, and knew the tremendous amount of work involved. We tackled this text with enthusiasm, but also with a degree of trepidation due to the daunting task.
Our goal in writing this textbook was not to have an exhaustive referenced rehash of material that is already present in text. Our goal was to provide a useful, clinical Veterinary MRI text. We were fortunate in starting magnetic resonance imaging of the brain in 1986. Magnetic resonance imaging for spontaneous brain tumors in dogs was a foundation for our research project. MRI continued to be a cornerstone of our research project to monitor the response of the brain tumor treatment and to evaluate normal tissue toxicities.
Washington State University had the oldest teaching hospital in North America in the 1990s. In 1996, we moved into a new facility that included a 1.0 Tesla superconducting magnetic resonance unit. We were the first veterinary medical college in an U.S. university with a state-of-the-art in-house superconducting MR unit. We were enthusiastic to expand beyond the imaging of brain tumors, and our initial efforts were in spinal disease. Our initial studies were not very good, and we had to methodically evaluate numerous pulse sequences and image planes to arrive at a clinically useful study. Magnetic resonance imaging was evolving rapidly in all fields, and some of the anatomical differences with our small patients necessitated a change from previous human protocols. We became comfortable in the spine, and then advanced into imaging for other conditions of the head, orthopedic disease, thorax, and abdomen. We also embarked on the imaging of the limbs of live adult horses. Our equine studies will not be covered in this textbook and will need to be treated in a separate volume.
The superior visualization of soft tissues of the body has allowed for the imaging of virtually all disease processes. The improved conspicuity allows clinicians of multiple disciplines to have clear visualization of the disease process. This text is to provide examples of our experiences that have been gained over the past 21 years. In addition to our experiences, some of the examples come from my active collaboration with other sites. These include the IAMS Pet Imaging Centers in Vienna, Virginia, Raleigh, North Carolina, and Redwood City, California. Examples have also been used from Dr. Michael Broome’s Advanced Veterinary Medical Imaging Center in Tustin, California. These centers, coupled with the Washington State University cases make up the bulk of the material for the figures in the text, but other images come from Dr. Kelley Collins, Veterinary Imaging Center in Ambler, Pennsylvania, Oakridge Veterinary Imaging in Edmond, Oklahoma, Tacoma Veterinary MRI in Tacoma, Washington, and Veterinary Neurological Centers in Phoenix, Arizona.
The images chosen are realistic examples of common abnormalities. We have endeavored to provide good quality images, but not ones that cannot be readily obtained virtually all superconducting magnets. There are no permanent magnet images due to lack of availability of such images in our files. The images are shown with the patients right on the viewers left, unless otherwise indicated. The images are generally shown with the dorsal anatomic area to the top of the image, even when acquired differently. If the dependence of the image is important, that will be given in the figure legend.
There is intentional overlap of some diseases in the various chapters. For example, neoplasia of a peripheral nerve may be covered in Chapter 2 (Section 3) on the peripheral nervous system, Chapter 3 on orthopedic disease, and Chapter 7 on MR imaging for cancer. The studies may have been requested for different reasons, that is loss of function, lameness, or for radiation therapy planning, and this redundancy should help the reader find the material for the clinical problem as presented.
We considered an exhaustive library of normal images, but discarded that notion. All studies have variability due to species, individual variation, technique, and volume averaging. Therefore, it is impossible to show an example that would fit all needs. We have given limited normal information, and have endeavored to illustrate common misunderstandings.
The text has limited information on physics, sequence selection, and artifacts. There are many superb texts that delve into these topics in great detail. We have only provided a skeleton of that material to facilitate the discussion of the case material presented in the various chapters. Magnetic resonance imaging is just now becoming an accepted modality throughout the veterinary profession. We have been fortunate to be among the early adaptors of this exciting technology. We hope this text will aid you in the continued exploration and discovery of new information.
We would like to thank Dr. Susan Kraft, DVM, PhD DACVR and Dr. Shannon Holmes for their superb contributions. Finally, we would like to thank the many students, interns, residents, and colleagues that helped us learn from our mistakes.