Cerebrovascular Ultrasound in Stroke Prevention and Treatment E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 790

Veröffentlichungsjahr: 2011

Beschreibung

Effective stroke therapy can be improved through real-time monitoring of the neurological and cardiovascular responses to treatment. This requires crucial knowledge on behalf of both the sonographer and stroke physician to make the best decisions for the patient so as to minimize the damage caused by the original stroke and the risk of further stroke. Cerebrovascular Ultrasound in Stroke Prevention and Treatment, Second Edition, takes a practical approach to the examination of patients, the interpretation of ultrasound studies and the application of cerebrovascular ultrasound in the development of management and treatment studies, assisting neurologists, radiologists, and ultrasonographers in stroke therapy.

Leseprobe

Contents

List of Contributors

Preface

Foreword

Neurosonology – dead or alive?

Preface to the First Edition

Foreword to the First Edition

Ultrasound: What’s in the Waveforms?

Acknowledgment

Introduction

References

Part I How to Perform Ultrasound Tests

1 Principles of Extracranial Ultrasound Examination

Introduction

Anatomy of the cerebrovascular arterial system

Components of ultrasound examination

Extracranial duplex ultrasound examination technique and scanning protocol

Color flow ultrasound evaluation of flow dynamics

Doppler spectral evaluation of flow dynamics

Extracranial duplex examination should provide the following data

Tips to improve accuracy

Tips for optimizing color flow set-up

References

2 Intracranial Cerebrovascular Ultrasound Examination Techniques

Introduction

TCD examination technique

Where to start?

Transtemporal insonation steps (Figure 2.5)

Transorbital insonation steps (Figure 2.6)

Transforaminal insonation steps (Figure 2.7)

Submandibular insonation steps (Figure 2.8)

Practical advice

M-mode or PMD/TCD examination technique

Transcranial color duplex imaging

TCDI examination technique

References

3 Anatomy of the Brain’s Arterial Supply

Introduction

The aortic arch

Variant great vessel origins and aortic arch anomalies

The anterior circulation

Internal carotid artery segments

Intracranial ICA branches

Anterior cerebral artery

Middle cerebral artery

The posterior circulation

Posterior cerebral artery

The circle of Willis

Pial to pial anastomotic flow

Primitive anastomoses

References

Part II Hemodynamic Principles

4 Integrated Assessment of Systemic and Intracranial Hemodynamics

Introduction

Principles of blood flow

The cardiac cycle

Arterial perfusion and venous return

Intrinsic cardiac determinants of blood flow

Neuro-endocrine mediation of cardiac output

Bedside assessment of systemic hemodynamics

Relationship between systemic and intracranial hemodynamics

References

5 Practical Models of Cerebral Hemodynamics and Waveform Recognition

Introduction

The driving force

Flow resistance

Pressure-flow relationship of stenosis

Flow velocity in stenosis

Vasomotor reactivity (VMR)

Cerebral autoregulation

Arterial bifurcations and collateral flow distribution

How to read waveforms

Specific waveforms

References

Part III Criteria for Interpretation

6 Diagnostic Criteria for Cerebrovascular Ultrasound

Introduction

Normal extracranial and intracranial findings

Carotid stenosis and plaque formation

Carotid stenosis measured by angiography

Carotid stenosis measured by ultrasound

Post-carotid endarterectomy assessment and carotid stents

Grading bilateral carotid stenosis

Tandem carotid lesions

Carotid artery occlusion and dissection

Arterial vasospasm and hyperemia

Criteria for vasospasm in other intracranial arteries

Cerebral embolization and detection of right to left shunts

Increased intracranial pressure (ICP)

Cerebral circulatory arrest

Arterial occlusion, recanalization and re-occlusion

Subclavian steal syndrome

Reversed Robin Hood syndrome

Summary of technical findings

The final interpretation

References

Part IV Ultrasound in Stroke Prevention and Treatment

7 Ultrasound in Stroke Prevention: TCD and Sickle Cell Disease

Introduction

STOP TCD protocol

How to perform TCD in children

Factors influencing cerebral blood flow velocities

STOP TCD scanning protocol steps

Reading STOP TCD

STOP criteria and the risk of stroke in children with HbSS

Frequently asked questions about STOP

References

8 Cardiovascular Risk Factors and Carotid Ultrasound

Introduction

Doppler ultrasound and screening for carotid stenosis in asymptomatic individuals

Asymptomatic carotid disease and risk of stroke and cardiovascular events

Carotid ultrasound criteria for detection of carotid stenosis

Gray-scale (B-mode) imaging of the atherosclerotic plaque

Carotid artery intima-media thickness

Summary

References

9 Applications of Functional Transcranial Doppler (fTCD)

Introduction

Physiological background

How to perform a fTCD investigation: technical considerations and practical recommendations

Validation studies

Limitations

Applications of fTCD

Conclusions

References

10 Transcranial Doppler in the Detection and Quantitation of Patent Foramen Ovale and Other Right-to-Left Circulatory Shunts

Introduction

Prevalence of PFO

PFO and ischemic stroke

PFO and migraine

PFO and decompression sickness

Methods of PFO detection

Contrast-enhanced TCD detection of right-to-left shunts

Shunt grading/quantitation

Clinical applications of TCD in RLS detection and quantitation

Summary

References

11 Ultrasound in Neurocritical Care

Introduction

Assessment of vasospasm

TCD for assessment of cerebral hemodynamics

Clinical outcome prediction and TCD

Duplex ultrasound imaging

Intracranial parenchymal assessment

Mass effect after stroke

Hemorrhagic transformation

Localization during ICU procedures

Brain death

Summary

References

12 Cerebral Vasospasm after Subarachnoid Hemorrhage

Introduction

Biologic and physiological aspects of vasospasm

Clinical and diagnostic features of DIND and vasospasm

Use of transcranial Doppler and cerebral blood flow studies for vasospasm

Options for treatment of vasospasm

Conclusions

References

13 Intra-Operative TCD Monitoring

Monitoring carotid endarterectomy

Carotid artery stenting (CAS)

Cardiac surgery monitoring

References

14 Intracranial Stenosis

Introduction

Focal intracranial disease

Diffuse intracranial disease

References

15 Ultrasound in Acute Stroke: Diagnosis, Reversed Robin Hood Syndrome and Sonothrombolysis

Introduction

Diagnosis of lesions amenable to intervention

Reversed Robin Hood syndrome

Other pathogenic mechanisms

Monitoring thrombolytic therapy with ultrasound

Ultrasound-enhanced thrombolysis

Gaseous microspheres and sonolysis

References

16 Ultrasound and Gaseous Microspheres

Introduction

Ultrasound scattering from gaseous µS

Contrast microspheres in the circulation

Resonance of contrast microspheres

Artifacts and contrast microbubbles

Summary

References

17 Neurosonology Pearls

Index

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Library of Congress Cataloging-in-Publication Data

Cerebrovascular Ultrasound in Stroke Prevention and Treatment

Edited by Andrei V. Alexandrov. – 2nd ed.

p.; cm.

Includes bibliographical references and index.

ISBN 978-1-4051-9576-8 (hardback)

1. Cerebrovascular disease–Ultrasonic imaging. I. Alexandrov, Andrei V.

[DNLM: 1. Stroke–ultrasonography. 2. Stroke–diagnosis. 3. Stroke–therapy.

WL 355 C41427 2010]

RC388.5.C4345 2004

616.8′107543–dc22

2010024035

A catalogue record for this book is available from the British Library.

List of Contributors

Robert J. Adams MD

Professor of Neurology

Medical University of South Carolina

Charleston, SC, USA

Anne W. Alexandrov PHD, FAAN

Professor and Director

NETSMART Program

Comprehensive Stroke Center

Department of Neurology

University of Alabama at Birmingham

Birmingham, AL, USA

Clotilde Balucani MD

Stroke and Neurosonology Fellow

Comprehensive Stroke Center

University of Alabama Hospital

Birmingham, AL, USA

and

PhD Student

Department of Neurology

University of Perugia

Perugia, Italy

Andrew D. Barreto MD

Assistant Professor, Director Neurosonology

Laboratory, Department of Neurology, Stroke

Division, University of Texas–Houston Medical

School

Houston, TX, USA

Joel Cure MD

Professor and Neuro-Radiologist

Department of Radiology

University of Alabama Hospital

Birmingham, AL, USA

Andrew Demchuk MD, FRCPC

Associate Professor of Neurology

Director, Stroke Program

Department of Clinical Neurosciences

University of Calgary

Calgary, Alberta, Canada

Flemming Forsberg PHD

Professor and Director of Research

Department of Radiology

Thomas Jefferson University

Philadelphia, PA, USA

Cindy J. Fuller PHD

Research Scientist

Swedish Heart and Vascular Institute

Seattle, WA, USA

Zsolt Garami MD

Director, TCD Center

The Methodist Hospital

Houston, TX, USA

James C. Grotta MD

Professor and Chairman, Department of

Neurology, Stroke Division, University of

Texas–Houston Medical School

Houston, TX, USA

Mark R. Harrigan MD

Assistant Professor of Neurosurgery and Radiology

University of Alabama at Birmingham

Birmingham, AL, USA

Jill T. Jesurum PHD

Scientific Director

Swedish Heart and Vascular Institute

Seattle, WA, USA

Anne M. Jones RN, BSN, RVT, RDMS

Lecturer, Department of Neurology

Wake Forrest University Medical Center

Winston-Salem, NC, USA

Annabelle Lao MD

Attending Neurologist

Santo Thomas University

Manila, Philippines

Alan B. Lumsden MD

Professor and Chairman, Department of

Cardiovascular Surgery

Medical Director, Methodist DeBakey Heart and

Vascular Center

The Methodist Hospital

Houston, TX, USA

Robert Mikulik MD, PHD

Director, Stroke Program

Department of Neurology

Masaryk University

Brno, Czech Republic

Marsha M. Neumyer BS, RVT, FSVU,

FAIUM, FSDMS

International Director

Vascular Diagnostic Educational Services

Harrisburg, PA, USA

David W. Newell MD

Professor of Neurosurgery

Department of Neurological Surgery

Director, Seattle Stroke Center

University of Washington

Seattle, WA, USA

Fenwick T. Nichols III MD

Professor, Department of Neurology

Medical College of Georgia

Augusta, GA, USA

Paola Palazzo MD

Department of Neurology

Campus Bio-Medico University

Rome, Italy

Joseph F. Polak MD, MPH

Professor of Radiology

New England Medical Center

Tufts University

Boston, MA, USA

Alice Robinson-Vaughn

NVT(C)

Chief Technologist

Neurovascular Ultrasound Laboratory

University of Alabama Hospital

Birmingham, AL, USA

Marta Rubiera, MD

Stroke Unit, Neurology Department,

Hospital Vall d’Hebron

Barcelona, Spain

Tatjana Rundek MD, PHD

Associate Professor of Neurology

Department of Neurology

Miller School of Medicine

University of Miami

Miami, FL, USA

Vijay K. Sharma MD, RVT

Director of Neurosonology

Division of Neurology

National University Hospital

Singapore and Chinese

University of Hong Kong

Prince of Wales Hospital

Hong Kong

China

Georgios Tsivgoulis MD, PHD, RVT

Adjunct Assistant Professor and Director of Stroke Research

Comprehensive Stroke Center

University of Alabama Hospital

Birmingham, AL, USA

and

Lecturer in Neurology

Democritus University of Thrace

Alexandroupolis, Greece

Konstantinos Vadikolias MD, PHD

Assistant Professor of Neurology

Democritus University of Thrace

Neurology Department

University Hospital

Alexandroupolis, Greece

K.S. Lawrence Wong MD

Professor of Neurology

Department of Medicine and

Therapeutics, Chinese

University of Hong Kong

Prince of Wales Hospital

Hong Kong

China

Preface

This edition was prepared during challenging times in my career. I took on the leadership position to organize the acute stroke care team at the University of Alabama Hospital, the home of Tinsley Harrison’s internal medicine and Champ Lyons’ surgery heritage, that is located in the buckle of the Stroke Belt of the United States. A number of accomplished physicians and scientists paid their dues in fighting this disease in Alabama prior to my arrival at UAB. The list (by no means complete) includes James Halsey, J. Garber Galbraith, Leland Clark, James Morawetz, Winfield Fisher, Gary Roubin, Dennis Doblar, Vijay Misra, Georg Deutsch, Camilo Gomez, Rodney Soto, Sean Orr, Joseph Horton, Michelle Robbin, Edward Faught and Robert Slaughter. Dr Ray Watts, Chairman of the Department of Neurology, with the help of Drs Halsey, Rebecca Sugg and Andrew Barreto, recruited me and my wife, Anne Alexandrov, to UAB in 2007.

Our goal was to build a Stroke Team standing up to a meaning of the words – Comprehensive Stroke Center. We started with education at multiple levels of health professionals about a proactive, “reasons to treat” approach to stroke, removing the word “diversion” from stroke patients access to UAB, instituting shared stroke assessment, treatment and prevention protocols across all physicians on service, opening a dedicated universal-bed concept Stroke Unit and engaging multi-disciplinary care providers in this process.

Prior to start of “code stroke” in 2007, only four intravenous tPAs and just one intra-arterial thrombolysis procedure were given at UAB Hospital comprising less than 3% and 0.5%, respectively, of consecutive stroke patients being treated with reperfusion therapies. In 2008, these numbers were 38 (13%) and 20 (7%) and in 2009 we reached 100 (20%) and 40 (9%).

This could not have happened without our Team members who share the same “find reasons to treat” philosophy towards stroke care: stroke attendings Karen Allbright, Damon Patterson, John Brockington, John Rothrock; our interventionalists Damon Patterson, Mark Harrigan, Joseph Horton, Ed Underwood, Vijay Misra; our neurologists who help at multiple levels, Ivan Lopez, Jennifer deWolfe, Harrison Walker; our clinical and research fellows Aaron Anderson (winner of the 2009 Golden Plumber Award for the best Neurology Resident performance on Stroke service), Luis Cava (2010 Golden Plumber), Thang Huy Nguyen (who also contributed photographs to this edition with his remarkable camera skills), Marta Rubiera, Yi Zhang, Clotilde Balucani, Paola Palazzo, Kristian Barlinn; our nurse practitioner and clinical trial coordinator Mary Brethour and April Sisson; our sonographers Alice Robinson-Vaughn, Limin Zhao; and our Stroke Center staff who try to keep up with all of us: Alexis Jernigan and Sarah Bullock.

A special thanks to Georgios Tsivgoulis, a superb stroke neurologist and sonographer who bravely followed me to Alabama, helped us start this process and continues to conduct very productive research with us and our gurus in biostatistics/epidemiology George and Virginia Howard; and to Anne Alexandrov who coordinates multiple clinical and research protocol developments, education of staff and for her pivotal role in creation of the universal-bed Stroke Unit.

Our Team includes all nurses: first on M8 under the leadership of Elizabeth Toomey and Beth Clarkson and now on the Stroke Unit under Kathy Langley, Jill Stewart and Velinda Block, who offered tremendous support to innovations in care and research being delivered in this Unit.

Other members of our Stroke Team include all of the University Emergency Medicine faculty physicians, residents and nurses among whom I particularly would like to mention Janyce Sanford, Sarah Nafziger, Christopher Rosco, Henry Wang and Andy Thomas for their continuing support and fighting many political battles for us; Neurosurgery Department faculty physicians, residents and the Neuro-Intensive Care Unit staff with particular acknowledgement of vascular neurosurgeons Winfield Fisher and Mark Harrigan; Neuro-Radiologists Glenn Roberson, Joseph Horton, Joseph Sullivan, Robert Chapman and Joel “The Oracle” Cure; the Neuro-Vascular Laboratory staff at the UAB Heart and Vascular Center; Vascular Surgeons under the leadership of Will Jordan; Neuro-Rehabilitation specialists Eugene Taub, Victor Mark and Bill Baker; Palliative Care Team staff and physicians Heather Herrington and Rodney Tucker; and of course the backbone of Stroke service – all our current Neurology Residents and graduates among whom I particularly would like to mention Andrew Barreto (now at UT-Houston, with whom we continue close collaboration), Bijay Pandy (2008 Golden Plumber), Tiffany Pineda (2009 Golden Plumber runner-up, for “No Ear-Plugs Needed” resident performance on stroke service), Victor Sung (2009 Golden Plumber runner-up) and Hayden Countryman Long (2010 Golden Plumber runner-up). Their endless efforts on the most difficult clinical rotation made a huge difference in many patient lives.

Andrei V. Alexandrov, MD, RVT

Birmingham, AL

Foreword

Neurosonology – dead or alive?

Alive and Kicking!

With the advent of modern imaging technologies and non-invasive assessment of extra- and intracranial brain vessels by both CT angiography and MR angiography, some clinical neuroscientists feel that this may initiate the end of the decades of neurosonology. Is this true or a misconception?

Back in the old days, more than 35 years ago, neurologists in Europe applied continuous wave sonography to explore cervical vessels, mostly the common carotid, the carotid bifurcation and the internal and external branches. Few even tried to insonate the vertebrals. With more and more advanced ultrasound technology, despite the major investments in CT imaging and, later on, MRI imaging, both pulse transcranial and B-mode-neurosonology were developed.

Of note, European neurologists, mostly in Scandinavia, Germany, Austria and Switzerland, made neurosonology part of the basic diagnostic techniques that neurologists offer, on the same level as EEG, EMG or evoked potential testing. Certification for physicians and, some time later, also for technicians was introduced. Basically, at the end of their 5-year training period, virtually every neurology resident in Germany will be an experienced neurosonologist, many of them certified by the National Ultrasound in Medicine Society.

In contrast, in North America, neurosonology was largely considered to be a technician’s area of expertise, with physicians only interpreting the results and putting them in perspective. Only in a few centers, such as Seattle and Houston, did academic neurosonography create their own school of physicians trained in ultrasound and applying this technique to their patients. This may, in the future, become more popular.

Sonography is not the tool for the one time assessment of the brain-supplying arteries and the intracranial vessels. This can be done more reliably with CTA and MRA. Neurosonology is a monitoring instrument which allows repetitive assessments without side effects and exposure to radiation during procedures such as in re-canalization therapies, in patients with dissections or floating thrombi or, with additional ultrasound contrast, in the monitoring of emboligenic conditions. Furthermore, there may be hope for a therapeutic application of ultrasound. First steps in that direction have been made, and more steps will follow. Finally, threeand four-dimensional techniques and evaluations may help with individualizing treatment decisions, when it comes to the description of plaque morphology and differentiating “hot” plaques from “resting” plaques.

In Europe, several textbooks on neurosonology are available, many of them in their 3rd or 4th edition. This 2nd edition of the book by Andrei Alexandrov and co-workers represents a valid and profound counterbalance to European neurosonology, putting the techniques and future applications into perspective and setting the case for a more physician-applied neurosonology. The book is balanced and comprehensive and therefore could become the standard neurosonology volume for North America. Maybe at some point in time, a joint neurosonology textbook with contributors from North America, Europe and also Asia will follow.

Werner Hacke, MD, PHD

Professor and Chairman

Department of Neurology

University of Heidelberg

Germany

February 2010

Preface to the First Edition

This book is about vascular examination of patients suffering from stroke and relevance of this information to treatment decisions. This book is for clinicians who are eager to learn, prepared to observe and would not stop explorations.

Ultrasound sharpens clinician’s ear and provides a stethoscope, an observation tool. And, like a microscope, an ultrasound probe needs a scientist to point it in the right direction. However, to paint a global picture, a complex ultrasound system also needs an artist to bring the art and science of medicine together. Ultrasound enables to monitor the cardiovascular system and brain responses to treatment in real time, a blessing on the way to develop stroke therapies and a handy tool to tailor treatment when the current evidence is meager.

I indebted to my friends and colleagues who spent countless time sharing their expertise in this book. Working with a Stroke Treatment Team is a thrill and this book is the result of many observations, often at obscene hours, that made us believe that stroke is treatable.

Andrei V. Alexandrov, MD

2004, Houston, TX

Foreword to the First Edition

Ultrasound: What’s in the Waveforms?

The greatest advances in understanding and treating stroke have occurred in the past 30 years. This progress has coincided with and largely resulted from our dramatically improved ability to diagnose stroke and its subtypes, characterize its location and severity and understand its causes rapidly, accurately and in real time. This has taken some of the charm out of clinical stroke care as the senior readers of this book will still remember even the most astute clinicians’ conclusions based on a careful history and physical exam proven wrong at the post mortem table. But the positive benefits of technology and improved diagnostic capability far exceed our nostalgia for the “good old days” when we relied mainly on our clinical acumen. What constitutes our improved ability to diagnose stroke? Unlike many other diseases, precise diagnosis of stroke depends almost entirely on imaging.

Our diagnostic capability took its greatest leap forward with the development of brain imaging, first with X-ray computed tomography and more recently with magnetic resonance imaging. Brain imaging has enabled us to quickly and accurately differentiate between infarct and hemorrhage, determine the location and surmise the probable cause and establish the age and severity of most strokes rapidly and painlessly. Brain imaging is now the first step in stroke diagnosis and treatment and has been called the “EKG of stroke.” This technology is now available in the vast majority of hospitals in the developed world and, more than any other component of our clinical management, distinguishes 21st century stroke care.

Physiologic imaging developed almost concomitantly with structural brain imaging. Our ability to investigate cerebral blood flow and metabolism using radio-labeled tracers enabled us to see that acute and chronic stroke is a dynamic and potentially reversible process that would eventually yield to timely and precise therapeutic intervention. Pioneering studies using xenon and positron emitting isotopes demonstrated reduced cerebral blood flow distal to chronic extracranial and intracranial occlusion or vasospasm, and, most importantly, revealed the “ischemic penumbra” of reversibly damaged brain tissue in acute stroke patients that has yielded so far to timely reperfusion and, at least experimentally, to so called “neuroprotective” therapies targeting downstream consequences of interrupted blood flow. Furthermore, the linkage of cerebral blood flow and metabolism discovered with physiologic imaging has generated our ability to carry out “functional imaging.” This technology is not only helping us understand the functional anatomy of simple and complex behaviors, but has also given visible proof of the plasticity of brain function. This has given a huge boost to research into treatment aimed at amplifying stroke recovery.

Imaging the vascular bed is the third critical aspect of stroke diagnosis. The seductive complexity of the brain draws our attention, but the stroke clinician must never lose sight of the fact that stroke is first and foremost a disease of the blood vessels nourishing that organ. Vascular imaging has been available to clinicians longer than our ability to image the brain parenchyma. Catheter arteriography can reveal the anatomy of extracranial and intracranial occlusive disease, aneurysms and arterio-venous malformations and for decades has been a standard part of the pre-operative evaluation of patients with severe forms of these conditions. However, it was not until the advent of “non-invasive” techniques, using ultrasound and more recently magnetic resonance and CT-angiography, that vascular imaging has become part of the routine evaluation of all stroke patients. Such testing has become critical to answer essential clinical questions that impact management of every stroke patient such as the cause of bleeding in patients with intracranial hemorrhage and the precise location, nature and severity of arterial occlusion or narrowing in patients with transient ischemic attack or ischemic stroke.

The advantages of ultrasound for vascular diagnosis are well known. It is a fast, portable, non-invasive, repeatable and inexpensive technique. The application of ultrasound to clinical stroke care over the past decades has revealed a number of clinical determinations that are best made by this technique and that directly impact on clinical decision-making. Among various clinical situations, the most established ones include:

the early detection and characterization of extracranial atherosclerosis and occlusive disease especially at the carotid bifurcation,the consequences of proximal arterial occlusive disease on the distal cerebral vasculature,the natural history and response to treatment of acute arterial occlusion that causes hyperacute stroke,the detection of microemboli associated with cardiac and aortic pathology and carotid artery surgical manipulation (and perhaps gauging response to anti-platelet therapy),selection of children with sickle cell disease for blood transfusion as an effective tool in primary stroke prevention, andthe time course and reversibility of cerebral vasospasm after subarachnoid hemorrhage.

Portable ultrasound machines and handy monitoring sets made it possible to bring this technology to bedside and observe remarkable flow changes in stroke patients in real time. However, the field of ultrasonic diagnosis also has it detractors and limitations. For many applications, ultrasound has not been thoroughly tested for its utility, accuracy and validity in multi-center studies. While the benefits of using this methodology for the above indications, as well as for others that undoubtedly will emerge as our exploration of stroke disease continues, may seem self-evident to those of us who live with ultrasound technology and use it every day, this is not so evident to others. Careful outcomes research investigating the accuracy and cost benefit of ultrasound is needed to establish the utility of this technique for any clinical situation where we surmise that it should be routine. Many such studies have been carried out and have established the value of ultrasound particularly for the clinical issues listed above. This book should help identify where such data exist, and more importantly, where more data is still needed.

Finally, early ultrasound technology was indirect, had poor resolution and had high rates of false positive and false negative results. Even now, the technique is “operator dependent” in terms of the accuracy and validity of its results. While, in fact, to some extent these concerns are true of all diagnostic imaging, these limitations have been particularly true of ultrasound. Newer technology has provided significant advances in this regard, but it is necessary for each and every laboratory to maintain strict quality control in order to maximize the information that this powerful technology can provide. This textbook provides a major advance in that regard. Written by experts in the field, it will provide sonographers with the tools needed to enhance the confidence of clinicians in utilizing ultrasound technology and the clinicians with additional information how to implement this technology in their everyday decision-making.

James C. Grotta, MD

2004, Houston, TX

Acknowledgment (First Edition)

I joined the University of Texas Stroke Treatment Team in 1996 and never regret the loss of life style or many sleepless nights. The best experience one can get is to work together with Team members who would race day or night to see and treat acute stroke patients breaking all speed limits and meeting any strict time windows. With countless hours spent together in the emergency department, angio rooms, specialized care units and late night diners we shared thoughts and debated various ways to treat acute cerebral ischemia.

These observations would never have happened without Jim Grotta, a visionary for stroke treatment, who started this Team long before I joined it. He has led us to the highest percentage of consecutive stroke patients being treated with thrombolytics to date. This work would have never been accomplished without those who made it happen in Houston, current and former Team members, many of whom are now heading their own Stroke Teams in the Unites States, Canada and other countries (I apologize for not listing many more Stroke Team members who worked hard in Houston prior to 1996): Fahmi Al-Senani, Scott Burgin, Alex Brunser, Sergio Calleja, Morgan Campbell, Chin-I Chen, Oleg Chernyshev, David Chiu, Ioannis Christou, Andrew Demchuk, Ashraf El-Mitwalli, Robert Felberg, Zsolt Garami, Christiana Hall, Susan Hickenbottom, Yasuki Iguchi, Jennifer Ireland, Scott Kasner, Derk Krieger, Lise Labiche, Marc Malkoff, Robert Mikulik, Lewis Morgenstern, Elizabeth Noser, Nicholas Okon, Paisith Piriyawat, Marc Ribo, Hashim Shaltoni, Ken Uchino, Carlos Villar-Cordova, Teddy Wein and Frank Yatsu.

The words Stroke Treatment Team would remain just words without acknowledging everyday work of nurses, who took care of our patients and who carried out our pivotal as well as negative clinical trials. The Team is blessed with outstanding nurses who keep physicians on their toes: Patti Bratina, Sheila Ford, Dawn Matherne, Robin Saiki, Sandi Shaw, Dora Vital and Anne Wojner.

The Team could never be complete without interventionalists, cardiovascular surgeons, neurosurgeons, critical care, emergency physicians, scientists and proactive hospital nurse administrators who also made an enormous effort to be there on time and to brain-storm creative ways to combat the most resistive clinical and scientific problems: Jaroslaw Aronowski, Eddy Cacayourin, Linda Chi, Guy Clifton, Tony Estrera, Tom Flanigan, Brent King, Dong Kim, Steve Koch, Bill Maggio, Joseph Nates, David Robinson, Hazim Safi, Richard Smalling, Joon Song and Roger Strong.

This work would also have never been possible without Houston Fire Department, City Paramedics and many Emergency Room nurses, physicians and neurology residents.

2004, Houston, TX

Practice of Ultrasound: an Introduction

A variety of ultrasound tests have been introduced for the detection and monitoring of cerebrovascular disease in the past 50 years [1–10]. Advantages of ultrasound testing include its non-invasive nature, portability, real-time information and versatility. Imagine that one can sample tissues and flow behavior in real time at a rate of 5000 times per second. So far, no other imaging modality in wide use for stroke today comes close to this temporal resolution. Furthermore, ultrasound waves contain a mechanical pressure momentum resulting in energy transmission to tissues that in itself can yield a therapeutic effect.

Current and disappointing reality is that when a stroke patient gets an ultrasound evaluation, it is often limited to assessment of the extracranial portion of the carotid arteries, with an even more limited look at the vertebral arteries. Evaluation of brain vessels is reduced to a snapshot offered by a non-invasive angiography, if any. While in training, physicians dealing with stroke are not getting enough exposure to learning cerebral hemodynamics and the vastness of mechanisms of how strokes occur or can be reversed beyond the meager choice of approved therapies. This edition, in addition to the first, is intended to cover the gap for vascular neurologists to learn how ultrasound can enrich their ability to diagnose, evaluate and treat stroke and for sonographers to understand what information clinicians need from their tests. From the clinical applications standpoint, cerebrovascular ultrasound at present can:

1 differentiate normal from diseased vessels and states,

2 uncover plaques and identify the most dangerous ones,

3 grade categories of stenosis in major pre-cerebral and intracranial vessels,

4 localize the disease process including acute occlusions,

5 detect progression of a variety of diseases, including cerebral circulatory arrest,

6 detect, localize and quantify cerebral embolism,

7 detect right-to-left shunts,

8 assess the ability of collateral circulation to maintain cerebral blood flow or succumb to steal and

9 monitor and even augment thrombolysis.

A single test procedure or a single transducer cannot yet accomplish all of these tasks. Sonographers have to learn how to use a combination of extracranial and intracranial tests and keep up with the progress in the field.

Prerequisites to a successful practice of cerebrovascular ultrasound include knowledge of anatomy, physiology of cardiovascular and nervous systems, fluid dynamics and pathological changes in a variety of cerebrovascular disorders [11–21] and also the basics of ultrasound physics and instrumentation [22–24]. No single textbook is sufficient in preparation for proficiency examinations, nor could it serve as a sole source of reference material in day-to-day practice. I use multiple sources and continue to learn from previously written texts (not limited indeed to the classic contributions referenced in this section) as well as continuing medical education conferences, research papers and presentations at numerous ultrasound and stroke-related meetings.

In the 6 years that have passed since the first edition of this book, I received multiple suggestions on how to improve it. Also, the aim of this second edition is to update the description of cerebrovascular ultrasound testing methods and criteria for interpretation and to illustrate how ultrasound provides information helpful in patient management.

The practice of ultrasound (both performance and interpretation) should be a mandatory part of the residency training for physicians of different specialties as well as the Vascular Neurology training pathway. It still remains problematic in the United States to have all neurology trainees learn these skills during residency while the depth of ultrasound education varies greatly worldwide. As a result, there is skepticism towards ultrasonography [25] that is largely based on the lack of knowledge of how to perform, interpret and use the results of ultrasound tests in clinical practice and research.

Indeed, ultrasound testing has shortcomings since it is very operator dependent. But so are most tests in medicine! The accuracy of ultrasound testing varies between practitioners of different skill, knowledge and experience. Even the most experienced of us are not invincible. Constant learning and improvement are keys to reaching the best possible outcomes of ultrasound testing.

Sonographers have to meet the requirements such set by the board examinations of the American Registry of Diagnostic Medical Sonographers (ARDMS, www.ardms.org) or other national and international boards and societies. Most vascular practitioners pass the Registered Vascular Technologist (RVT) examination that focuses mostly on vascular ultrasound “from jaw to toe” leaving transcranial Doppler (TCD) largely untested. International or regional requirements for technologists’ credentials also vary. The American Society of Neuroimaging and the Neurosonology Research Group of the World Federation of Neurology are making progress in providing certification examinations on all continents where there is an interest in verifying the knowledge and skills of physicians and sonographers.

Interpreting physicians have to demonstrate competence through training such as Fellowship or by completing the required number of hours of continuing medical education in ultrasound methods and supervised interpretation of a set number of cases for each imaging modality. These requirements are outlined in the regulatory documents of the Intersocietal Commission of Accreditation of Vascular Laboratories (ICAVL, www.icavl.org) that recognizes two physician credentials outlined below as qualifications to serve as a director of a vascular ultrasound laboratory.

The American Society of Neuroimaging (www.asnweb.org) also offers a peer-reviewed multiplechoice proficiency examination in neurosonology that covers physics, clinical application and interpretation of the carotid/vertebral and transcranial ultrasound methods. This is the only organization to date that assesses knowledge specific to the neurovascular field including TCD. The Registered Physician Vascular Interpreter (RPVI) examination by ARDMS tests peripheral and carotid vascular testing knowledge and does not cover TCD (www.ardms.org).

In addition to credentialing, consistent application, local validation of ultrasound testing and interpretation and continuing quality improvement are the keys to successful practices [26].

Ultrasound offers a wealth of information, including realtime assessment of patho-physiological changes and monitoring of patients with cerebrovascular diseases. Often, this information finds no place in clinical decision-making as skeptics would say, “it has not been tested in randomized clinical trials.” Not everything that we do as clinicians can or should be tested in these trials. Ultrasound can be very helpful in clinical decision-making if the results are provided in a timely fashion and the practicing physicians are prepared to use this information to select the best management strategy and often to go beyond “proven” (often meager) standards in the best interests of the patient.

I consider TCD and carotid duplex as an extension of the neurological examination as these tests enable me to confirm the vascular origin of patient symptoms, detect and localize the disease process and monitor the progress of therapies. This approach is outlined in detail in a companion book entitled Neurovascular Ultrasound Examinationand Waveform Interpretation. That book also contains basics of ultrasound physics and fluid dynamics complementary to this edition and provides more illustrative case examples of diagnostic findings and considerations in differential diagnosis.

I am indebted to my peers, colleagues who challenged my thinking, those who became my mentors through ongoing debates and ultimately friends: Marsha Neumeyer, Joseph Polak, John Pellerito and Charles Tegeler. The numerous courses that we taught together made me in the first place continuously learn ultrasound and re-think what I thought I knew. Likewise on the clinical side, Andrew Demchuk, James Grotta, Carlos Molina, Peter Schellinger and my team at UAB contributed greatly to my continuing explorations of stroke. I also gratefully acknowledge all contributors to this book who donated their time and shared their expertise – their chapters bring you on a continuing journey of learning stroke and ultrasound. I would like to thank Rune Aaslid, PhD, pioneer of TCD, for generously providing his original drawing of the circle of Willis, as well as his input in advising me on cerebral hemodynamics.

In short, ultrasound remains an exciting field that offers new possibilities and challenges. It requires investment of time and effort to learn, yet it is rewarding in practice if you master these skills. You will start to see the disease process from new angles as real-time patho-physiological changes unfold and hopefully become a better practitioner.

Andrei V. Alexandrov, MD, RVT

Birmingham, AL

References

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2 Spencer MP, Reid JM, Davis DL, et al. Cervical carotid imaging with a continuous-wave Doppler flowmeter. Stroke 1974;5:145–54.

3 Barber FE, Baker DW, Nation AW, et al. Ultrasonic duplex echoDoppler scanner. IEEE Trans Biomed Eng 1974;21(2):109–13.

4 Budingen HJ, von Reutern GM, Freund HJ. Diagnosis of cerebro-vascular lesions by ultrasonic methods. Int J Neurol 1977;11(2–3):206–18.

5 Aaslid R, Markwalder TM, Nornes H. Noninvasive transcranial Doppler ultrasound recording of flow velocity in basal cerebral arteries. J Neurosurg 1982;57:769–74.

6 Spence JD, Coates RK, Pexman JA.Doppler flow maps of the carotid artery compared with the findings on angiography. CanJ Surg 1983;26:556–8.

7 Bogdahn U, Becker G, Schlief R, et al. Contrast-enhanced transcranial color-coded real-time sonography. Stroke 1993;24:676–84.

8 Rubin JM, Bude RO, Carson PL, et al. Power Doppler US: a potentially useful alternative to mean frequency-based color Doppler US. Radiology 1994;190(3):853–6.

9 Burns PN. Harmonic imaging with ultrasound contrast agents. Clin Radiol 1996;51:50–5.

10 O’Leary DH, Polak JF, Kronmal RA, et al. Carotid-artery intima and media thickness as a risk factor for myocardial infarction and stroke in older adults. Cardiovascular Health Study Collaborative Research Group. N Engl J Med 1999;340(1):14–22.

11 Krayenbuehl H, Yasargil MG. Cerebral Angiography, 2nd edn. Stuttgart: Georg Thieme, 1982.

12 Bernstein EF.Vascular Diagnosis, 4th edn. St. Louis, MO: MosbyYear Book, 1993.

13 Polak JF. Peripheral Vascular Sonography: a Practical Guide. Baltimore, MD: Williams & Wilkins, 1992.

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17 Tegeler CH, Babikian VL, Gomez CR. Neurosonology. St. Louis: Mosby, 1996.

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20 Bartels E. Color-Coded Duplex Ultrasonography of the Cerebral Arteries: Atlas and Manual. Stuttgart: Schattauer, 1999.

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22 Edelman SK. Understanding Ultrasound Physics, 2nd edn. The Woodlands, TX: ESP, 1997.

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24 Zagzebski JA. Essentials of Ultrasound Physics. St. Louis, MO: Mosby, 1997.

25 Ringelstein EB. Skepticism toward carotid ultrasonography. A virtue, an attitude or fanaticism? Stroke 1995;26: 1743–6.

26 Katanick SL. Accreditation of vascular ultrasound laboratories. In: Tegeler CH, Babikian VL, Gomez CR, eds, Neurosonology. St. Louis, MO: Mosby, 1996:484–88.

I

How to Perform Ultrasound Tests

1

Principles of Extracranial Ultrasound Examination

Andrei V. Alexandrov1, Alice Robinson-Vaughn1, Clotilde Balucani2 & Marsha M. Neumyer3

1University of Alabama Hospital, Birmingham, AL, USA

2University of Alabama Hospital, Birmingham, AL, USA and University of Perugia, Perugia, Italy

3Vascular Diagnostic Educational Services, Harrisburg, PA, USA

Introduction

A simple observation gives origins to clinical examinations, analysis and scientific exploration. Being able to observe Nature at work or in distress often offers clues that clinicians and scientists need to get an idea as to what could be going on and come up with a hypothesis to explain it. Ultrasound, with its unprecedented temporal resolution, is an elegant tool to probe living tissues. This first chapter describes how we evaluate the extracranial vasculature, then subsequent chapters continue the journey into cerebral vessels, hemodynamics and specific disease states.

Anatomy of the cerebrovascular arterial system

The choice of transducer placement and subsequent repositioning determines the success of visualizing the target structures and staying with the spatial course of the pre-cerebral vessels. Therefore, sonographers performing vascular ultrasound examinations must think “in 3-D,” or three dimensions, about the vessel being investigated and put together transducer positioning with vessel intercept and further “go with the structure or flow” to complete scanning.