Problem_Solving-0

无水印完整版 资料 新概念英语资料下载李居明饿命改运学pdf成本会计期末资料社会工作导论资料工程结算所需资料清单 需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m 1600 John F. Kennedy Blvd. Ste 1800 Philadelphia, PA 19103-2899 PROBLEM SOLVING IN MUSCULOSKELETAL IMAGING ISBN: 978-0-323-04034-1 Copyright © 2008 by Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permissions may be sought directly from Elsevier’s Rights Department: phone: (+1) 215 239 3804 (U.S.) or (+44) 1865 843830 (U.K.); fax: (+44) 1865 853333; e-mail: healthpermissions@elsevier.com. You may also complete your request on-line via the Elsevier Web site at http://www.elsevier.com/permissions. Working together to grow libraries in developing countries www.elsevier.com | www.bookaid.org | www.sabre.org Notice Knowledge and best practice in this fi eld are constantly changing. As new research and experience broaden our knowledge, changes in practice, treatment and drug therapy may become necessary or appropriate. Readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of the practitioner, relying on their own experience and knowledge of the patient, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the Authors assume any liability for any injury and/or damage to persons or property arising out of or related to any use of the material contained in this book. Library of Congress Cataloging-in-Publication Data Morrison, William B. Problem solving in musculoskeletal imaging / William B. Morrison, Timothy G. Sanders.—1st ed. p. ; cm. Includes bibliographical references and index. ISBN 978-0-323-04034-1 1. Musculoskeletal system—Imaging. 2. Musculoskeletal System—Diseases—Diagnosis. 3. Problem solving. I. Sanders, Timothy G. II. Title. [DNLM: 1. Musculoskeletal Diseases—diagnosis. 2. Magnetic Resonance Imaging—methods. 3. Musculoskeletal System. WE 141 M883p 2008] RC925.7.M68 2008 616.7′075—dc22 2007042922 Acquisitions Editor: Rebecca Gaertner Developmental Editor: Elizabeth Hart Project Manager: Mary Stermel Design Direction: Steven Stave Marketing Manager: Catalina Nolte Printed in China. Last digit is the print number: 9 8 7 6 5 4 3 2 1 FM-A04034.indd iv 4/16/2008 2:16:06 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m Kenneth A. Buckwalter, MD Professor Department of Radiology Indiana University School of Medicine University Hospital Indianapolis, IN Angela Gopez, MD Assistant Professor Department of Radiology Thomas Jefferson University Hospital Philadelphia, PA Eoin C Kavanagh, MRPCI, FFR, RCSI Consultant Radiologist and Senior Lecturer Mater Misericordiae Hospital Dublin, Ireland W. James Malone, DO Academic Chief, Musculoskeletal Imaging Department of Radiology Geisinger Medical Center Danville, PA Levon N. Nazarian, MD, FACR Professor and Vice Chairman for Education Department of Radiology Thomas Jefferson University Hospital Philadelphia, PA Imran M. Omar, MD Assistant Professor Department of Radiology Northwestern Memorial Hospital Chicago, IL Paul Shieh, MD Staff Radiologist Community Medical Center Saint Barnabas Health Care System Toms River, NJ Adam C. Zoga, MD Associate Professor Department of Radiology Thomas Jefferson University Hospital Philadelphia, PA Contributors v FM-A04034.indd v 4/16/2008 2:16:06 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m vii Preface The “Problem Solving” series by Elsevier is a new type of teaching tool: a series of texts in different disci- plines that strive to distill the authors’ experience and approach to clinical challenges rather than merely index the imaging appearance of injury and disease. This format is diffi cult to achieve in all areas, and therefore texts within this series will incorporate dif- ferent variations of this concept. Our musculoskeletal edition, for example, is roughly divided into three areas: technical issues and optimization, approach to musculoskeletal diseases, and advanced joint imaging. The fi rst technical chapter teaches a practical meth- odology for improving image quality across modali- ties, as well as providing examples of how the radiologist can use the modality to answer specifi c clinical questions. The attached CD is an extension of this chapter; it includes material that aids the radi- ologist in day-to-day clinical operations—patient questionnaires, dictation templates, and MRI/CT pro- tocols, including pictorial examples of positioning and plane selection. Additional chapters provide instruction on performance of arthrography and bone/soft tissue biopsy. The approach chapters address general categories of disease, including arthritis, tumor and infection; these chapters attempt to provide the reader with tips and thought processes associated with diagnosis of these conditions. The joint-oriented chapters strive to teach the reader how to interpret advanced imaging studies on a high level, similar to a dedicated musculoskeletal radiologist. Figures are formatted in an easy-to-read way analogous to a PowerPoint slide rather than tra- ditional book fi gures with dozens of arrows and long legends. Problem Solving in Musculoskeletal Imaging is intended to be read cover-to-cover. The entire work is an effort to enable readers to “get into the mind” of a bone radiologist, so that they may provide high- level service to their patients and referring clinicians. We hope that we have achieved this goal. We are eternally grateful to our teachers and contributors who helped make this book a reality. William B. Morrison, MD Timothy G. Sanders, MD FM-A04034.indd vii 4/16/2008 2:16:07 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m ix Acknowledgments I am very grateful to David Karasick, MD, Diane Deely, MD, and Alex Dresner, PhD, for lending me their extensive expertise. I am also indebted forevermore to David and Diane, as well as Mark Schweitzer, MD, for providing teaching, mentoring, and continuing support throughout my career. All my other teachers, colleagues, and friends deserve credit for their guidance—you know who you are—your martini is waiting! Thanks to dancers Phil Colucci and Emily Hayden of the Pennsylvania Ballet for modeling arthrographic technique. Special thanks to Anne Dugan for her assistance. —WBM I would like to acknowledge two very special mentors and friends, Robert Miller, MD, at the University of Florida for fi rst sparking my interest in musculoskeletal radiology, and Phillip Tirman, MD, for helping to jumpstart my academic career. My time in radiology has been much richer as a result of these two individuals. I would like to acknowledge the entire Air Force community: for the fun, the education, and the varied opportunities during 25 great years. Finally, I would like to thank my family; my parents for their steadfast support throughout the years, and of course my wife, DeAun, and daughters, Kelly and Courtney, for their continued understanding and support during the prepara- tion of this book. —TGS FM-A04034.indd ix 4/16/2008 2:16:07 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m 3 SE C T IO N I CHAPTER OUTLINE Magnetic Resonance Imaging 4 High-Field versus Low-Field Scanners 4 Advantages and Disadvantages of 3 T Scanners for Musculoskeletal Imaging 7 Coils 8 Imaging Sequence Selection 8 Spatial Resolution versus Contrast—Which to Choose? 8 Spin-Echo Imaging 11 Fast Spin-Echo Imaging 11 Short Tau Inversion Recovery 13 Gradient-Echo Imaging 14 MR Arthrography 17 Optimizing Signal-to-Noise Ratio 18 How to Reduce Artifacts Seen on Musculoskeletal MR Imaging 24 Artifacts Related to Fat Suppression 24 Artifacts Related to Motion 26 Blur Artifact 28 Artifacts Related to Signal Loss: Field Cutoff/Coil Malposition 29 Magic Angle Phenomenon 29 Magnetic Susceptibility Artifact 30 Chemical Shift Misregistration Artifact 32 Using Artifacts to Your Advantage 33 How to Take Advantage of Magnetic Susceptibility Artifact 33 How to Take Advantage of Chemical Shift Artifact 34 Special Planes/Positions 34 Computed Tomography 36 Basics of Multidetector CT 36 Musculoskeletal Ultrasound 47 Chapter 1 OPTIMIZATION OF CLINICAL MUSCULOSKELETAL IMAGING Ch001-A04034.indd 3 4/16/2008 2:16:30 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m Section I ADVANCED MODALITIES: Protocols and Optimization4 MAGNETIC RESONANCE IMAGING When protocols are created or altered for musculo- skeletal magnetic resonance (MR) imaging examina- tions, consideration should be given to the type of MR scanner being used (e.g., high fi eld or low fi eld), available surface coils and their confi gurations, and technologist experience. Beyond that, thought should be given to what specifi c information is needed from the examination, taking into account the clinical history and what is the appropriate fi eld of view to answer the question. Is high spatial resolution required to answer the question, or is high contrast between structures more important? Planes and sequences should be selected to optimize relevant anatomy and pathology, optimizing signal-to-noise ratio (SNR). Finally, consideration should be given as to whether intravenous or intra-articular contrast is necessary, and whether any specialized sequences, planes, or positions would be advantageous. This section deals with each of these issues in addition to artifacts and their minimization. Sample protocols with suggested plane selection are available on the accompanying CD. High-Field versus Low-Field Scanners Scanners come in a variety of fi eld strengths, and options are available for various gradient strengths and slew rates intended to optimize scanning. Soft- ware options are often available at additional cost. These issues can cause confusion when selecting a scanner for purchase. In addition, different manufac- turers have different terminology for sequences, magnet homogeneity, and other physical features that make it diffi cult to perform an “apples to apples” comparison. However, rarely does musculoskeletal imaging come into consideration when purchasing a scanner. Typically, neurologic and body imaging applications are those that guide scanner selection and purchase, and musculoskeletal imaging is a sec- ondary consideration. A basic understanding of MR physics principles is generally all that is needed to optimize musculoskeletal imaging protocols, no matter what machine is used. The differences between high-fi eld and low-fi eld scanners are extremely impor- tant in musculoskeletal imaging; advantages and dis- advantages are summarized in Table 1-1. Low-fi eld scanners, that is, lower than 0.7 tesla (T), have diffi culty performing standard presaturation- type frequency selective fat suppression because the signal peaks for the protons in water and fat are closely approximated. This is very important because musculoskeletal radiologists generally prefer to apply fat suppression on T2-weighted images to highlight fl uid and edema. In addition, because fat is ubiqui- tous in the musculoskeletal system, fat suppression is preferred when gadolinium is injected intravenously or into a joint. As such, this can be a signifi cant limi- tation of low-fi eld scanners. Instead of T2-weighted fast spin-echo fat-suppressed imaging, which is a standard in musculoskeletal radiology, short tau inversion recovery (STIR) imaging is used to achieve fl uid conspicuity, but at the expense of lowered reso- lution or a larger fi eld of view. Alternatively, fl uid conspicuity can be achieved without fat suppression by increasing echo time (TE), about 100 to 120 msec. However, this is at the expense of the SNR, which decreases as TE is raised. This creates diffi culty in visualizing small cartilage lesions. One should not expect to consistently see small cartilage defects on a low-fi eld scanner. Without fat suppression on T1-weighted images, visualization of intravenously or intra-articularly administered contrast can be diffi cult, limiting appli- cations such as tumor/infection imaging and MR arthrography. Also, there is relatively lower signal overall. To compensate, this requires increasing the number of signal averages to increase signal at the expense of increased imaging time, which can increase motion artifact in the extremities. Length of examina- tions is generally much greater on low-fi eld scanners and may not be as useful for uncooperative patients. Coil options are often limited on low-fi eld scanners, with a small variety of multipurpose surface coils available for imaging various musculoskeletal struc- Table 1-1 Low-Field MRI: Advantages and Disadvantages Advantages Lower magnetic susceptibility artifact High T1 contrast Ease of positioning Obese patients (up to 500-pound weight limit) Eccentric body parts easier to center Disadvantages Diffi culty performing “standard” fat suppression Lower overall signal—longer scan times needed (motion artifact can be an issue) Low resolution (imaging of cartilage, small structures such as labrum limited) Ch001-A04034.indd 4 4/16/2008 2:16:31 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m SE C T IO N I Chapter 1 OPTIMIZATION OF CLINICAL MUSCULOSKELETAL IMAGING 5 tures. This can result in an inappropriately large fi eld of view and low resolution. Nevertheless, there are some advantages to muscu- loskeletal imaging on low-fi eld scanners. T1 contrast is actually superior to that of high-fi eld scanners, although this is a relatively minor advantage in prac- tice; in fact, improved T1 contrast can be disadvanta- geous. Consider evaluation of the knee on a low-fi eld system; on a T1-weighted sequence fl uid may appear black, blending with signal of the menisci (Fig. 1-1). Because of lower fi eld strength, artifact from metal may be decreased compared with high-fi eld scanners, and imaging patients who have prostheses, screws, or other orthopedic hardware can actually be improved by directing these patients to a low-fi eld scanner. Keep in mind that advances in gradient technology at high fi elds have offset many of these advantages for high-fi eld scanners. Chemical shift artifact is also decreased at low fi eld. Moreover—and what is possibly the most impor- tant consideration—is the gantry size and table weight limit of low-fi eld scanners, which generally offer an open environment and a weight limit of up to 500 pounds. For obese patients, no other imaging options may be available. This is mainly an issue in the United States. Regarding fat suppression, many low-fi eld scanners offer a software option based on the Dixon technique, which acquires an in-phase and out-of- phase image, and through subtraction post-process- ing, obtains a fat-suppressed image (Fig. 1-2). If the subtraction is performed from images acquired in the same series no subtraction errors occur, and the images and degree of fat suppression are generally excellent. In fact, if the radiologist’s intention is to perform MR arthrography on a low-fi eld scanner, strong consideration should be given to acquiring this post-processing software. Newer generations of low-fi eld scanners can actually separate the fat and water peaks, performing true fat saturation, but this has been suboptimal compared with the Dixon technique. Extremity scanners are also available, which are generally low fi eld at about 0.2 T; although they are low cost and provide a high degree of patient comfort, low image quality corresponds to the low strength. Also, the narrow bore of the magnet limits scanning Discoid meniscus with tear? Fluid can be black on T1w images on low- field scanners, similar to signal of meniscus STIR No T1 Figure 1-1 0.3 T MRI of the knee. Low-fi eld scanners have better T1 contrast than high-fi eld units. However, this can have a detrimental effect on joint imaging. Ch001-A04034.indd 5 4/16/2008 2:16:31 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m Section I ADVANCED MODALITIES: Protocols and Optimization6 Susceptibility artifact from prior rotator cuff repair In-phase Fatty marrow retains signal on out-of-phase Red marrow loses signal on out-of-phase Out-of-phase Partial-thickness undersurface retear Gadolinium stands out Fat- suppressed Black muscle, black fluid characterize a water-suppressed image Water- suppressed Figure 1-2 MR arthrogram on a 0.3 T system. Dixon technique for fat-water separation. An in-phase and out-of- phase image is acquired (useful for marrow evaluation) as well as a fat-suppressed and a water-suppressed image. The fat- suppressed image is ideal for use in MR arthrography on low-fi eld scanners. However, as a gradient-echo sequence, it is prone to susceptibility artifact from metal, air, blood products, and calcium. Ch001-A04034.indd 6 4/16/2008 2:16:32 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m SE C T IO N I Chapter 1 OPTIMIZATION OF CLINICAL MUSCULOSKELETAL IMAGING 7 to wrists/hands, elbows, ankles/feet and knees. However, a 1.0 T extremity scanner is available that provides good image quality comparable to that achieved with closed 1.5 T scanners (Fig. 1-3). Other open confi guration 1.0 T scanners are also available. Advantages and Disadvantages of 3 T Scanners for Musculoskeletal Imaging There are some distinct advantages of 3 T MRI for musculoskeletal imaging. The high fi eld strength pro- vides high SNR over all imaging sequences, allowing an increase in the matrix, a decrease in slice thickness, and a decrease in fi eld of view, providing increased resolution; ultimately, high resolution is a major key to success in musculoskeletal radiology (Fig. 1-4). Alternatively, one can use the signal surplus to decrease number of excitations (NEX), thereby short- ening examination time and increasing patient throughput. However, protocols must be altered somewhat to account for the different physical prop- erties of the 3 T environment. For example, the high fi eld strength at 3 T accentuates susceptibility artifact from metal, limiting evaluation of orthopedic hard- ware. In addition, chemical shift artifacts may be increased, resulting in black-white effect at fat–water Triangular fibrocartilage tear Figure 1-4 High-resolution 3 T imaging of the thumb using a small solonoid coil. Improved knowledge of anatomic detail and microstructural pathology will be required once this degree of resolution is routinely achieved. (Courtesy of Ivan Dimitrov, Best, the Netherlands, Philips.) Figure 1-3 Coronal gradient-recalled echo image of the wrist acquired with a 1.0-T dedicated extremity scanner. (Courtesy of ONI and Joel Newman, Boston, MA.) Ch001-A04034.indd 7 4/16/2008 2:16:33 PM 无水印完整版资料需者请发邮件：wzxidian@gmail.com Doc uCo m P DF Tria l ww w.p dfw izar d.co m Section I ADVANCED MODALITIES: Protocols and Optimization8 interfaces. This can be eliminated if fat suppression is used; alternatively, one can make the pixels smaller to reduce this artifact by increasing