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Ultrasound in Obstetrics and Gynecology: A Practical Approach Editor Alfred Abuhamad, MD with contributions from Rabih Chaoui, MD Philippe Jeanty, MD Dario Paladini, MD Editorial Assistant Emily Walsh, BA, MA Forward by Professor John Hobbins, MD first edition Copyright © 2014 Alfred Abuhamad All rights reserved ISBN-14: 978-0-692-26142-2 2 FORWARD Ultrasound was introduced into the practice of Obstetrics and Gynecology over four decades ago, and along the way its impact has risen exponentially to a point where it is rare even for a low risk, uncomplicated, patient to make it through pregnancy without having at least two ultrasound examinations and a high risk patient to have less than four scans. Most important is the pivotal role ultrasound plays in our obstetrical decision-making and in GYN one rarely hangs one’s hat on a diagnosis made by a pelvic exam alone. While building a career in OB/GYN, residency represents, by far, the most impactful step. Recently, I asked graduating residents from around the country interested in our perinatal fellowship to rate their training in ultrasound (from 1 to 10). The average was 3. Only one of the twenty three individuals I interviewed rated their training as 9. Why? Because in resident training programs the importance of ultrasound is often downplayed in favor of other facets of the specialty, and enlightened faculty members interested in imparting ultrasound knowledge and skills are challenged by the woeful lack of resource material on the basics of obstetrical and gynecological ultrasound. Yes, students or program directors can easily find some directed texts on the fetal CNS, heart, skeletal dysplasias, and high risk pregnancy, in general, but locating a text that deals with the nitty- gritty of day-to-day scanning has been challenging. Until now! Dr. Abuhamad and colleagues have come up with a resource that really fills the void perfectly. This text concisely covers the physics of ultrasound and how to exploit the features of today’s equipment to optimize every image, while using methods to assure that the fetus is exposed to the lowest ultrasound energies. It tackles something as mundane as how to hold a transducer properly, as well as providing clever hints on how, for example, to insert the vaginal transducer into the umbilicus to better image the fetus in an obese patient. The authors outline beautifully what ultrasound will enable us to see in a normal first trimester, second trimester, and third trimester pregnancy, as well as in a non-pregnant uterus and adnexa – and they give tips along the way on how to cone in on the essential items to piece together a clinical picture. They also masterfully cover many of the common clinical surprises that a sonographer and sonologist might encounter. Most importantly, the text is embellished with some of the most beautiful ultrasound images I have seen in any textbook. If you are an experienced sonographer or sonologist who wants a booster dose of ultrasound knowledge or a quasi-novice thrown suddenly into an ultrasound-heavy clinical practice, or ANY student wanting to learn more about OB/GYN ultrasound, this book will provide the necessary backdrop to help you become a more savvy and proficient practitioner. I cannot wait to get this into the hands of every one of our residents and fellows. - John C. Hobbins, MD 3 BOOK EDITORS Alfred Abuhamad, MD Dr. Alfred Abuhamad is Professor and Chairman of the Department of Obstetrics and Gynecology and Vice Dean for Clinical Affairs at Eastern Virginia Medical School, Norfolk, Virginia. Dr. Abuhamad is recognized internationally as a leading expert in imaging in Obstetrics & Gynecology and Fetal Echocardiography. He is the president elect of the Society of Ultrasound in Medical Education and immediate past-President of the American Institute of Ultrasound in Medicine. Dr. Abuhamad established the International Society of Ultrasound in Obstetrics and Gynecology Outreach Committee and led several ultrasound training activities in the developing world. Emily Walsh Emily Walsh has been working at Eastern Virginia Medical School for seven years, three of those years in the Department of Obstetrics and Gynecology. She holds a Bachelors of Arts and Masters of Arts in Communications, with a focus in Digital Media. Emily has been published in Alberta Katherine Magazine out of Jacksonville, Florida and was a contributing writer for Regent University’s The Daily Runner. Emily is also the Co-Founder of LE Literary Services, which offers publishing and editorial assistance to authors. 4 CONTRIBUTING AUTHORS Rabih Chaoui, MD Dr. Rabih Chaoui is Co-Director of the Center of Prenatal Diagnosis and Human Genetics in Berlin, Germany. A leading international authority on fetal imaging, Dr. Chaoui has contributed extensively to the literature in obstetrical imaging and fetal echocardiography and played a major role in ultrasound education globally as the chairman of the International Society of Ultrasound in Obstetrics and Gynecology’s Education Committee from 2009 - 2013. Philippe Jeanty, MD Dr. Philippe Jeanty is a world renowned radiologist with extensive expertise in women’s imaging. He has published extensively and authored several books in ultrasound. He is the founder of The Fetus.net, an open access site that disseminates information on fetal ultrasound. Dr. Jeanty is considered an international expert in the field of ultrasound, he has mentored several fellows and led many ultrasound education and training courses in low-resource settings. Dario Paladini, MD Prof. Dario Paladini is Associate Professor in Obstetrics and Gynecology. He is currently the Director of the Fetal Medicine and Surgery Unit at Gaslini Children's Hospital in Genoa, Italy. Prof. Paladini is a leading international expert in fetal imaging, from 3D/4D ultrasound to fetal cardiology, and neurosonography to early assessment. He has authored more than 150 peer-review articles in fetal imaging and gynecological ultrasound (IOTA trials) and Gynecologic Oncology. Prof. Paladini is also co-author of Ultrasound of Fetal Anomalies, a prized textbook on fetal anomalies in its 2nd edition. Finally, he is deeply involved in OBGYN ultrasound education globally as the Chairman of the International Society of Ultrasound in Obstetrics and Gynecology’s Education Committee (2004-2009) and Chairmen of the Italian Society of Ultrasound in OBGYN (SIEOG; 2010-2012). 5 PREFACE “You give but little when you give of your possessions. It is when you give of yourself that you truly give”. Khalil Gibran - The Prophet I embarked on this journey with one focus in mind, to produce an educational resource designed to enhance the theoretical and practical knowledge of ultrasound with the goal of enhancing care for women around the world. Ultrasound has assumed an integral part of obstetrics and gynecology, whether in identifying a high-risk pregnancy or in assessing the non-pregnant uterus and adnexae. The proper application of ultrasound requires an in depth knowledge of the technology and practical skills for image acquisition, both of which are deficient in many parts of the world. This e-book is intended to fill this gap in all settings. This e-book has three main sections; the first three chapters focus on the technical and practical use of ultrasound with a review of the physical principles of sound, the practical approach to the ultrasound equipment, and the technical aspect of performing the ultrasound examination. The second section, chapters four to ten, addresses the obstetric ultrasound examination and the third section, chapters eleven to fourteen, addresses the gynecologic ultrasound examination. The last chapter shows how to write an ultrasound report, a key component of the examination. Two chapters in particular, chapters ten and fourteen, present a stepwise-standardized approach to the basic obstetric and gynecologic ultrasound examinations respectively. The book is filled with descriptive figures, tables, and tips that the authors use in their daily ultrasound practice and have been accrued through many years of experience. Many contributed to the success of this book, first and foremost, my friends and co-authors, Rabih Chaoui, Philippe Jeanty, and Dario Paladini who collectively possess an immense knowledge in ultrasound, are recognized as giants in this field, and provided book content and editorial review. Second, Ms. Emily Walsh, who helped design the book, organize the figures and tables, and produce the product that you see today. Her artistic abilities, time commitment, and focused approach made this project a reality. Third, the Marketing Department at Eastern Virginia Medical School, who coordinated the website to host and support the book. Last, but not least, my wife, Sharon, who was a great support and unselfishly allowed me to spend countless hours on this project. A special thank you to the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) for the support they provide to ultrasound education in low-resource settings around the world and for many ISUOG volunteers who donated their time and expertise to this cause. It is primarily through these activities that I have seen first-hand the impact of ultrasound in women’s healthcare. Many women around the world approach pregnancy and delivery with fear of death or serious injury. If through this educational resource, we are able to impact a single life, then our efforts would have been justified. - Alfred Abuhamad, MD. 6 To Sharon, For your unwavering support, dedication, and commitment to ultrasound With love 7 CONTENTS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Forward Book Editors Contributing Authors Preface Basic Physical Principles of Medical Ultrasound . . . . . . . . . . . . . . . 9 Basic Characteristics of the Ultrasound Equipment . . . . . . . . . . . . 30 Technical Aspects of the Ultrasound Examination . . . . . . . . . . . . . 43 Ultrasound in the First Trimester. . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Ultrasound in the Second Trimester . . . . . . . . . . . . . . . . . . . . . . . . 91 Ultrasound in the Third Trimester . . . . . . . . . . . . . . . . . . . . . . . . . . 122 Ultrasound Evaluation of Twin Gestation . . . . . . . . . . . . . . . . . . . . 134 Placental Abnormalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Amniotic Fluid Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Stepwise Standardized Approach to the Basic Obstetric Ultrasound Examination in the Second and Third Trimester of Pregnancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 Ultrasound of the Non-Pregnant Uterus . . . . . . . . . . . . . . . . . . . . . 212 Ultrasound Evaluation of the Adnexae . . . . . . . . . . . . . . . . . . . . . . 253 Ectopic Pregnancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 Stepwise Approach to the Basic Ultrasound Examination of the Female Pelvis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 Writing the Ultrasound Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 8 BASIC PHYSICAL PRINCIPLES OF MEDICAL ULTRASOUND 1 INTRODUCTION The introduction of ultrasound to obstetrics and gynecology has made tremendous impact to patient care as it allowed imaging of the fetus and placenta in obstetrics and maternal internal organs in gynecology with such clarity to allow advanced diagnosis and also to guide various life saving interventions. Understanding the physical principles of ultrasound is essential for a basic knowledge of instrument control and also for understanding safety and bioeffects of this technology. In this chapter, we present the basic concepts of the physical principles of ultrasound, define important terminology, review the safety and bioeffects and report on ultrasound statements of national and international organizations. PHYSICAL CHARACTERISTICS OF SOUND Sound is a mechanical wave that travels in a medium in a longitudinal and straight-line fashion. When a sound travels through a medium, the molecules of that medium are alternately compressed (squeezed) and rarefied (stretched). Sound cannot travel in a vacuum; it requires a medium for transmission, as the sound wave is a mechanical energy that is transmitted from one molecule to another. It is important to note that the molecules do not move as the sound wave passes through them, they oscillate back and forth, forming zones of compression and rarefaction in the medium. Seven acoustic parameters describe the characteristics of a sound wave. Table 1.1 lists these characteristics. TABLE 1.1 - Characteristics of Sound Waves Frequency Period Amplitude Power Intensity Wavelength Propagation speed Frequency of a sound wave is the number of cycles that occurs in one second (Figure 1.1). The unit Hertz is 1 cycle / second. Frequency is an important characteristic of sound in ultrasound imaging as it affects penetration of sound and image quality. Period of a sound wave is related to Chapter 1: Basic Physical Principles of Medical Ultrasound 9 the time that a wave takes to vibrate up and down and thus is reciprocally related to frequency. For instance, a sound wave with a frequency of 10 Hertz will have a period of 1/10 second. Amplitude, power and intensity are three wave characteristics that relate to the strength of a sound wave. Amplitude is defined by the difference between the peak (maximum) or trough (minimum) of the wave and the average value (Figure 1.2). The peak or crest, represents the zone of compression and the trough represents the zone of rarefaction (Figure 1.2). Units of amplitudes are expressed in pressure parameters (Pascals) and in clinical imaging in million Pascals (MPa). The amplitude of a sound wave diminishes as sound propagates through the body. Power is the rate of energy transferred through the sound wave and is expressed in Watts. Power is proportional to the amplitude squared of a sound wave. Power can be altered up or down by a control on the ultrasound machine. Intensity is the concentration of energy in a sound wave and thus is dependent on the power and the cross sectional area of the sound beam. The intensity of a sound beam is thus calculated by dividing the power of a sound beam (Watts) by its cross sectional area (cm2), expressed in units of W/cm2. The wavelength of a sound wave is the length of a wave and is defined as the distance of a complete cycle. It is designated by the symbol lambda (λ), is expressed in mm in clinical settings (Figure 1.3), and can be calculated by dividing the velocity of the wave by the frequency of the wave (λ = v/f). The propagation speed is the distance that a sound wave travels through a specified medium in 1 second. Figure 1.1: Frequency of sound is the number of cycles per second (s) and is expressed in Hertz (1 cycle / sec). In Wave A, the frequency is 2 cycles per sec or 2 Hertz and in wave B the frequency is 3 cycles per sec or 3 Hertz. The double arrows denote sound wavelengths, described in figure 1.3. Chapter 1: Basic Physical Principles of Medical Ultrasound 10