RF Coils for MRI E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: EMR Books
• Sprache: Englisch

Seitenzahl: 1102

Veröffentlichungsjahr: 2012

Beschreibung

The content of this volume has been added to eMagRes (formerly Encyclopedia of Magnetic Resonance) - the ultimate online resource for NMR and MRI.

To date there is no single reference aimed at teaching the art of applications guided coil design for use in MRI. This RF Coils for MRI handbook is intended to become this reference. 

Heretofore, much of the know-how of RF coil design is bottled up in various industry and academic laboratories around the world. Some of this information on coil technologies and applications techniques has been disseminated through the literature, while more of this knowledge has been withheld for competitive or proprietary advantage. Of the published works, the record of technology development is often incomplete and misleading, accurate referencing and attribution assignment being tantamount to admission of patent infringement in the commercial arena.  Accordingly, the literature on RF coil design is fragmented and confusing.  There are no texts and few courses offered to teach this material. Mastery of the art and science of RF coil design is perhaps best achieved through the learning that comes with a long career in the field at multiple places of employment…until now.

RF Coils for MRI combines the lifetime understanding and expertise of many of the senior designers in the field into a single, practical training manual. It informs the engineer on part numbers and sources of component materials, equipment, engineering services and consulting to enable anyone with electronics bench experience to build, test and interface a coil. The handbook teaches the MR system user how to safely and successfully implement the coil for its intended application. The comprehensive articles also include information required by the scientist or physician to predict respective experiment or clinical performance of a coil for a variety of common applications.  It is expected that RF Coils for MRI becomes an important resource for engineers, technicians, scientists, and physicians wanting to safely and successfully buy or build and use MR coils in the clinic or laboratory.  Similarly, this guidebook provides teaching material for students, fellows and residents wanting to better understand the theory and operation of RF coils.

Many of the articles have been written by the pioneers and developers of coils, arrays and probes, so this is all first hand information! The handbook serves as an expository guide for hands-on radiologists, radiographers, physicians, engineers, medical physicists, technologists, and for anyone with interests in building or selecting and using RF coils to achieve best clinical or experimental results.

About EMR Handbooks / eMagRes Handbooks 

The Encyclopedia of Magnetic Resonance (up to 2012) and eMagRes (from 2013 onward) publish a wide range of online articles on all aspects of magnetic resonance in physics, chemistry, biology and medicine. The existence of this large number of articles, written by experts in various fields, is enabling the publication of a series of EMR Handbooks / eMagRes Handbooks on specific areas of NMR and MRI. The chapters of each of these handbooks will comprise a carefully chosen selection of articles from eMagRes. In consultation with the eMagRes Editorial Board, the EMR Handbooks / eMagRes Handbooks  are coherently planned in advance by specially-selected Editors, and new articles are written (together with updates of some already existing articles) to give appropriate complete coverage. The handbooks are intended to be of value and interest to research students, postdoctoral fellows and other researchers learning about the scientific area in question and undertaking relevant experiments, whether in academia or industry.

Have the content of this Handbook and the complete content of eMagRes at your fingertips!
Visit: www.wileyonlinelibrary.com/ref/eMagRes

View other eMagRes publications here

Leseprobe

EMR Handbooks

Based on the Encyclopedia of Magnetic Resonance (EMR), this monograph series focuses on hot topics and major developments in modern magnetic resonance and its many applications. Each volume in the series will have a specific focus in either general NMR or MRI, with coverage of applications in the key scientific disciplines of physics, chemistry, biology or medicine. All the material published in this series, plus additional content, will be available in the online version of EMR, although in a slightly different format.

Previous EMR Handbooks

NMR CrystallographyEdited by Robin K. Harris, Roderick E. Wasylishen, Melinda J. DuerISBN 978–0-470–69961–4

Multidimensional NMR Methods for the Solution StateEdited by Gareth A. Morris, James W. EmsleyISBN 978–0-470–77075–7

Solid-State NMR Studies of BiopolymersEdited by Ann E. McDermott, Tatyana PolenovaISBN 978–0-470–72122–3

NMR of Quadrupolar Nuclei in Solid MaterialsEdited by Roderick E. Wasylishen, Sharon E. Ashbrook, Stephen WimperisISBN 978–0-470–97398–1

Forthcoming EMR Handbooks

MRI of Tissues with ShortT2 and T2*Edited by Ian R. Young, Gary Fullerton and Graeme M. BydderISBN 978–0-470–68835–9

Encyclopedia of Magnetic Resonance

Edited by Robin K. Harris, Roderick E. Wasylishen, Edwin D. Becker, John R. Griffiths, Vivian S. Lee, Ian R. Young, Ann E. McDermott, Tatyana Polenova, James W. Emsley, George A. Gray, Gareth A. Morris, Melinda J. Duer and Bernard C. Gerstein.

The Encyclopedia of Magnetic Resonance (EMR) is based on the original printed Encyclopedia of Nuclear Magnetic Resonance, which was first published in 1996 with an update volume added in 2000. EMR was launched online in 2007 with all the material that had previously appeared in print. New updates have since been and will be added on a regular basis throughout the year to keep the content up to date with current developments. Nuclear was dropped from the title to reflect the increasing prominence of MRI and other medical applications. This allows the editors to expand beyond the traditional borders of NMR to MRI and MRS, as well as to EPR and other modalities. EMR covers all aspects of magnetic resonance, with articles on the fundamental principles, the techniques and their applications in all areas of physics, chemistry, biology and medicine for both general NMR and MRI. Additionally, articles on the history of the subject are included.

For more information see: www.wileyonlinelibrary.com/ref/emr

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Front cover image credit:Cover images were kindly supplied by Brandon Tramm and Jinfeng Tian.

Library of Congress Cataloging-in-Publication Data

RF coils for MRI / editors, J. Thomas Vaughan, John R. Griffiths. p. ; cm.

Includes bibliographical references and index. ISBN 978–0-470–77076–4 (cloth)

I. Vaughan, J. Thomas (John Thomas), 1957- II. Griffiths, John R., 1945-

III. Encyclopedia of magnetic resonance.

[DNLM: 1. Magnetic Resonance Imaging – methods. 2. Electromagnetic Fields.

3. Magnetic Resonance Spectroscopy – instrumentation. 4. Radio Waves.

5. Transducers. WN 185]

616.07’548 – dc23

2012015267

A catalogue record for this book is available from the British Library. ISBN-13: 978–0-470–77076–4

Set in 9.5/11.5 pt Times by Laserwords (Private) Limited, Chennai, India Printed and bound in Singapore by Markono Print Media Pte Ltd

Encyclopedia of Magnetic Resonance

Editorial Board

Editors-in-Chief

Robin K. HarrisUniversity of DurhamDurhamUK

Roderick E. WasylishenUniversity of AlbertaEdmonton, AlbertaCanada

Section EditorsSOLID-STATE NMR & PHYSICS

Melinda J. DuerUniversity of CambridgeCambridgeUK

Bernard C. GersteinAmes, IAUSA

SOLUTION-STATE NMR & CHEMISTRY

James W. EmsleyUniversity of SouthamptonSouthamptonUK

George A. GrayVarian Inc.Palo Alto, CAUSA

Gareth A. MorrisUniversity of ManchesterManchesterUK

BIOCHEMICAL NMR

Ann E. McDermottColumbia UniversityNew York, NYUSA

Tatyana PolenovaUniversity of DelawareNewark, DEUSA

MRI & MRS

John R. GriffithsCancer Research UKCambridge Research InstituteCambridgeUK

Ian R. YoungImperial CollegeLondonUK

HISTORICAL PERSPECTIVES

Edwin D. BeckerNational Institutes of HealthBethesda, MDUSA

International Advisory Board

David M. Grant (Chairman)University of UtahSalt Lake City, UTUSA

Isao AndoTokyo Institute of TechnologyTokyoJapan

Adriaan BaxNational Institutes of HealthBethesda, MDUSA

Chris BoeschUniversity of BernBernSwitzerland

Paul A. BottomleyJohns Hopkins UniversityBaltimore, MDUSA

William G. BradleyUCSD Medical CenterSan Diego, CAUSA

Graeme M. BydderUCSD Medical CenterSan Diego, CAUSA

Paul T. Callaghan (deceased)Victoria University of WellingtonWellingtonNew Zealand

Richard R. ErnstEidgenössische Technische Hochschule (ETH)ZürichSwitzerland

Ray FreemanUniversity of CambridgeCambridgeUK

Lucio FrydmanWeizmann Institute of ScienceRehovotIsrael

Maurice GoldmanVillebon sur YvetteFrance

Harald GüntherUniversität SiegenSiegenGermany

Herbert Y. KresselHarvard Medical SchoolBoston, MAUSA

C. Leon PartainVanderbilt University Medical CenterNashville, TNUSA

Alexander PinesUniversity of California at BerkeleyBerkeley, CAUSA

George K. RaddaUniversity of OxfordOxfordUK

Hans Wolfgang SpiessMax-Planck Institute of Polymer ResearchMainzGermany

Charles P. SlichterUniversity of Illinois at Urbana-ChampaignUrbana, ILUSA

John S. WaughMassachusetts Institute of Technology (MIT)Cambridge, MAUSA

Bernd WrackmeyerUniversität BayreuthBayreuthGermany

Kurt WüuthrichThe Scripps Research InstituteLa Jolla, CAUSAandETH ZüurichZürichSwitzerland

Contents

Cover

Title

Copyright

Contributors

Series Preface

Volume Preface

Part A: Surface Coils

1 An Historical Introduction to Surface Coils: The Early Days

2 Radiofrequency Coils for NMR: A Peripatetic History of Their Twists and Turns

3 Quadrature Surface Coils

4 Double-Tuned Surface Coils

5 Nested Surface Coils for Multinuclear NMR

6 Quadrature Transverse Electromagnetic (TEM) Surface Coils

Part B: Loop Arrays

7 Receiver Loop Arrays

8 Coil Array Design for Parallel Imaging: Theory and Applications

9 Transceiver Loop Arrays

10 Characterization of Multichannel Coil Arrays on the Benchtop

Part C: Volume Coils

11 Birdcage Volume Coil Design

12 Double-Tuned Birdcage Coils: Construction and Tuning

13 TEM Body Coils

14 TEM Arrays, Design and Implementation

15 TEM Transceiver Head Array Coils for Ultra High Magnetic Fields

16 Transverse Electromagnetic (TEM) Coils for Extremities

17 Antennas as Surface Array Elements for Body Imaging at Ultra-high Field Strengths

Part D: Special Purpose Coils

18 Catheter Coils

19 Microcoils

20 Cryogenic and Superconducting Coils for MRI

21 Litz Coils for High Resolution and Animal Probes, Especially for Double Resonance

22 Millipede Coils

Part E: Coil Interface Circuits

23 Receiver Design for MR

24 Radiofrequency Power Amplifiers for NMR and MRI

25 Impedance Matching and Baluns

Part F: Coil Modeling and Evaluation

26 Radiofrequency MRI Coil Analysis: A Standard Procedure

27 Practical Electromagnetic Modeling Methods

28 Radiofrequency Fields and SAR for Bird Cages

29 RF Field Modeling for Double-Tuned Volume Coils

30 Radiofrequency Fields and SAR for Transverse Electromagnetic (TEM) Surface Coils

31 TEM Coil Fields and SAR

Part G: RF Safety

32 RF Device Safety and Compatibility

33 Radiofrequency Heating Models and Measurements

Index

Contributors

Joseph J. H. Ackerman

Department of Chemistry, Campus Box 1134, Washington University, Saint Louis, MO 63130, USA

Chapter 1: An Historical Introduction to Surface Coils: The Early Days

Gregor Adriany

Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA

Chapter 15: TEM Transceiver Head Array Coils for Ultra High Magnetic Fields

Can Eyup Akgun

Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA

Chapter 30: Radiofrequency Fields and SAR for Transverse Electromagnetic (TEM) Surface Coils

Ergin Atalar

Electrical & Electronics Engineering Department, Bilkent University, Ankara, TR-06800, Turkey

Chapter 18: Catheter Coils

Nikolai I. Avdievich

Department of Neurosurgery, Yale University, New Haven, CT 06520, USA

Chapter 6: Quadrature Transverse Electromagnetic (TEM) Surface CoilsChapter 16: Transverse Electromagnetic (TEM) Coils for Extremities

Barbara L. Beck

McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA

Chapter 4: Double-Tuned Surface Coils

C. A. T. van den Berg

Department of Radiotherapy, University Medical Center Utrecht, Utrecht 3508GA, The Netherlands

Chapter 17: Antennas as Surface Array Elements for Body Imaging at Ultra-high Field Strengths

Christopher M. Collins

Department of Radiology, The Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA

Chapter 3: Quadrature Surface Coils

F. David Doty

Doty Scientific Inc., Columbia, SC 29229, USA

Chapter 21: Litz Coils for High Resolution and Animal Probes, Especially for Double Resonance

Randy Duensing

Invivo Corporation, Gainesville, FL 32608, USA

Chapter 9: Transceiver Loop Arrays

George Entzminger Jr

Doty Scientific Inc., Columbia, SC 29229, USA

Chapter 21: Litz Coils for High Resolution and Animal Probes, Especially for Double Resonance

Eiichi Fukushima

ABQMR, Albuquerque, NM 87106, USA

Chapter 2: Radiofrequency Coils for NMR: A Peripatetic History of Their Twists and Turns

Mark A. Griswold

Department of Radiology, Case Western Reserve University, Cleveland, OH 44106, USA

Chapter 10: Characterization of Multichannel Coil Arrays on the Benchtop

Rolf Gruetter

Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland

Department of Radiology, University of Lausanne, CH-1015 Lausanne, Switzerland

Department of Radiology, University of Geneva, CH-1211 Geneva, Switzerland

Chapter 5: Nested Surface Coils for Multinuclear NMR

David I. Hoult

Institute for Biodiagnostics, National Research Council Canada, Winnipeg, Manitoba, MB R3B 1Y6, Canada

Chapter 23: Receiver Design for MR

Tamer S. Ibrahim

Departments of Bioengineering and Radiology, University of Pittsburgh, Pittsburgh, PA 15213, USA

Chapter 28: Radiofrequency Fields and SAR for Bird Cages

Jian-Ming Jin

Department of Electrical and Computer Engineering, University of Illinois, 1406 West Green Street, Urbana, IL 61801, USA

Chapter 27: Practical Electromagnetic Modeling Methods

Sven Junge

Bruker Biospin MRI GmbH, Ettlingen 76275, Germany

Chapter 20: Cryogenic and Superconducting Coils for MRI

Riccardo Lattanzi

New York University School of Medicine, New York, NY 10016, USA

Chapter 8: Coil Array Design for Parallel Imaging: Theory and Applications

Rostislav A. Lemdiasov

Insight Neuroimaging Systems, 11 Canterbury St., Worcester, MA 01610, USA

Chapter 26: Radiofrequency MRI Coil Analysis: A Standard Procedure

Wanzhan Liu

Medtronic Inc., Minneapolis, MN 55126, USA

Chapter 29: RF Field Modeling for Double-Tuned Volume Coils

Reinhold Ludwig

ECE Department, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA

Chapter 26: Radiofrequency MRI Coil Analysis: A Standard Procedure

Arthur W. Magill

Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland

Department of Radiology, University of Lausanne, CH-1015 Lausanne, Switzerland

Department of Radiology, University of Geneva, CH-1211 Geneva, Switzerland

Chapter 5: Nested Surface Coils for Multinuclear NMR

Joseph Murphy-Boesch

National Institutes of Health, Bethesda, MD 20892, USA

Chapter 12: Double-Tuned Birdcage Coils: Construction and Tuning

Daniel P. Myer

Communication Power Corporation (CPC), Hauppauge, NY 11788, USA

Chapter 24: Radiofrequency Power Amplifiers for NMR and MRI

John Nyenhuis

School of Electrical and Computer Engineering, Purdue University, WestLafayette, IN 47907, USA

Chapter 32: RF Device Safety and Compatibility

Michael A. Ohliger

University of California San Francisco, San Francisco, CA 94143, USA

Chapter 8: Coil Array Design for Parallel Imaging: Theory and Applications

David M. Peterson

McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA

Chapter 25: Impedance Matching and Baluns

A. J. E. Raaijmakers

Department of Radiotherapy, University Medical Center Utrecht, Utrecht 3508GA, The Netherlands

Chapter 17: Antennas as Surface Array Elements for Body Imaging at Ultra-high Field Strengths

Devashish Shrivastava

Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA

Chapter 33: Radiofrequency Heating Models and Measurements

Carl Snyder

Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA

Chapter 14: TEM Arrays, Design and Implementation

Daniel K. Sodickson

New York University School of Medicine, New York, NY 10016, USA

Chapter 8: Coil Array Design for Parallel Imaging: Theory and Applications

Jinfeng Tian

Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA

Chapter 31: TEM Coil Fields and SAR

J. Thomas Vaughan

Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA

Chapter 13: TEM Body CoilsChapter 33: Radiofrequency Heating Models and Measurements

Andrew G. Webb

Department of Radiology, Leiden University Medical Center, Leiden2333, The Netherlands

Chapter 3: Quadrature Surface CoilsChapter 19: Microcoils

Graham C. Wiggins

New York University School of Medicine, New York, NY 10016, USA

Chapter 8: Coil Array Design for Parallel Imaging: Theory and Applications

Ernest W. H. Wong

Agilent Technologies, Santa Clara, CA 95051, USA

Chapter 22: Millipede Coils

Steven M. Wright

Texas A&M University, College Station, TX 77845, USA

Chapter 7: Receiver Loop Arrays

Nicola De Zanche

Alberta Health Services and University of Alberta, Edmonton, Alberta, AB T6G 1Z2, Canada

Chapter 11: Birdcage Volume Coil Design

Abbreviations and Acronyms

1Q

Single-Quantum

2D

Two Dimensional

2QF-COSY

Double-Quantum-Filtered Correlation Spectroscopy

AAG

Ala-Ala-Gly

ABCs

Absorbing Boundary Conditions

ABMS

Anisotropy of the Bulk Magnetic Susceptibility

ACR

American College of Radiology

ADC

Analog-to-digital Converter

ADF

Amsterdam Density Functional

ADRF

Adiabatic Demagnetization in the Rotating Frame

AlN

Aluminum Nitride

AP

Anterior-Posterior

APW

Augmented Plane Wave Method

ARP

Adiabatic Rapid Passage

ARRL

American Radio Relay League

ATC

American Technical Ceramic

AWE

Asymptotic Waveform Evaluation

BCS

Bardeen -Cooper-Schrieffer

BeO

Beryllium Oxide

BHP

Balanced High Pass

BHTMs

Bioheat Transfer Models

BLEW

Burum, Linder & Ernst (Windowless pulse sequence)

BLP

Balanced Low Pass

BLYP

Becke, Lee, Yang, Parr

BO

Bridging Oxygen

BOM

Bond Orbital Model

BPP

B loembergen - Purcell - Pound

BR-24

Burum & Rhim (pulse sequence)

CAS

Crystal Axis System

CB

Conduction Band

CEA

Atomic Energy Commission

CEE

Convective Energy Equation

CF1T

Center-fed One-turn

CG

Conjugate

CH

Choline

CI

Confidence Interval

cLC

Capillary Liquid Chromatography

CMRR

Center for Magnetic Resonance Research

CODEX

Centerband-only Detection of Exchange Experiment

COSY

Correlation Spectroscopy

CP

Circular Polarization

CP

Cross Polarization

CPMAS

Cross Polarization and Magic Angle Spinning

CPMG

Carr-Purcell-Meiboom-Gill

Cr

Creatine

CRAMPS

Combined Rotation and Multiple-Pulse Spectroscopy

CRC

Counter-rotating Current

CS

Chemical Shift

CSA

Chemical Shift Anisotropy

CST

Chemical Shift Tensor

CST

Computer Simulation Technology

CT

Central Transition

CT

Contact Time

CTMAS

Central Transition Magic Angle Spinning

CW

Continuous Wave

CYCLOPS

Cyclically Ordered Phase Sequence

D

Dipolar

DAH

Dynamic Angle Hopping

DANTE

Delays Alternating with Nutations for Tailored Excitation

DAS

Dynamic Angle Spinning

DD

Dipole-Dipole

DDC

Dual Directional Coupler

DEAR

Dipolar Exchange-Assisted Recoupling

DEISM

Direct Enhancement of Integer-Spin Magnetization

DEPT

Distortionless Enhancement by Polarization Transfer

DFS

Double Frequency Sweeps

DFT

Density Functional Theory

DFT

Discrete Fourier Transform

DMS

Dilute Magnetic Semiconductors

DNP

Dynamic Nuclear Polarization

DOR

Double Rotation

DOS

Density of States

DPPC

Dipalmitoylphosphatidylcholine

DQ

Double-Quantum

DQC

Double-Quantum Coherence

DQF

Double-Quantum Filter

DR-NQR

Double-Resonance Nuclear Quadrupole Resonance

DRESS

Depth-resolved Surface Coil Spectroscopy

DRSE

Dipolar-Rotational Spin Echoes

DSPC

Distearoyl-sn-Glycero-3-Phosphatidylcholine

EFG

Electric Field Gradient

EM

Electromagnetic

EMC

Electromagnetic Compatibility

EMF

Electromotive Force

EMI

Electromagnetic Interference

ENDOR

Electron-Nucleus Double Resonance

EP

Electrophysiology

EPI

Echo Planar Images

EPR

Electron Paramagnetic Resonance

ER

End-ring Mode

EXAFS

Extended X-Ray Absorption Fine Structure

FAM

Fast Amplitude Modulation

FC

Fermi-Contact

FDA

Food and Drug Administration

FDTD

Finite Difference Time Domain

FEA

Finite Element Analysis

FEM

Finite Element Method

FFLO

Fulde-Ferrell-Larkin-Ovchinnikov

FFT

Fast Fourier Transform

FID

Free Induction Decay

FIR

Finite Impulse Response

FIT

Finite Integration Technique

FLASH

Fast Low Angle SHot

FML

Fast Motion Limit

fMRI

Functional Magnetic Resonance Imaging

FOQI

First-Order Quadrupolar Interaction

FOV

Field of View

FSLG

Frequency-Switched Lee Goldburg

FSW

Fourier Series Window

FT

Fourier Transform

FWD

Forward

FWHM

Full-width Half-maximum

GBHTM

Generic Bioheat Transfer Model

GGA

Generalized Gradient Approximation

GIPAW

Gauge Including Projector Augmented Waves

GRAPPA

Generalized Auto-calibrating Partially Parallel Acquisition

GRE

Gradient Echo

GRP

Glass-reinforced Plastic

HDOR

Heteronuclear Dipolar-Order Rotor-Encoding

HETCOR

Heteronuclear Correlation

HF

Hartree-Fock

HLW

High-Level Waste

HMQC

Heteronuclear Multiple Quantum Correlation

HMQC

Heteronuclear Multiple-Quantum Coherence

HMT

Hexamethylenetetramine

HOHAHA

Homonuclear Hartman-Hahn

HORROR

Homonuclear Rotary Resonance

HP

High-pass

HPBC

High Pass Birdcage

HS

Hyperbolic Secant

HSQC

Heteronuclear Single-Quantum Coherence

HTS

High-temperature Superconducting

IBMS

Isotropic Bulk Magnetic Susceptibility

ICNIRP

International Commission of Non-Ionizing Radiation Protection

ICRF

Inductively Coupled RF

ID

Inside Diameter

IEC

International Electro-technical Commission

INADEQUATE

Incredible Natural Abundance Double Quantum Transfer Experiment

INEPT

Insensitive Nuclei Enhanced by Polarization Transfer

INEPT-HSQC

Insensitive Nuclei Enhanced by Polarization Transfer-Heteronuclear Single-Quantum Correlation

IR

Infrared

ISIS

Image-selected In Vivo Spectroscopy

ISMRM

International Society of Magnetic Resonance in Medicine

ISNR

Intrinsic Signal-to-noise Ratio

KSAs

Knight Shifts and Associated Anisotropies

LG-CP

Lee-Goldberg CP

LMTO

Linear Muffin Tin Orbital

LO

Local Oscillator

LP

Low-pass

LR

Left-Right

LT

Low Temperature

MAH

Magic Angle Hopping

MAS

Magic Angle Spinning

MAS-J-HMQC

Magic Angle Spinning-J-Heteronuclear Multiple Quantum Coherence

MAS-J-HSQC

Magic Angle Spinning-J-Single Quantum Coherence

MD

Molecular Dynamics

MGH

Massachusetts General Hospital

MIL

Materials of the Institute Lavoisier

MIT

Metal-Insulator Transition

Series Preface

The Encyclopedia of Nuclear Magnetic Resonance was published in eight volumes in 1996, in part to celebrate the fiftieth anniversary of the first publications in NMR in January 1946. Volume 1 contained an historical overview and ca. 200 short personal articles by prominent NMR practitioners, while the remaining seven volumes comprise ca. 500 articles on a wide variety of topics in NMR (including MRI). Two “spin-off” volumes incorporating the articles on MRI and MRS (together with some new ones) were published in 2000 and a ninth volume was brought out in 2002. In 2006, the decision was taken to publish all the articles electronically (i.e. on the World Wide Web) and this was carried out in 2007. Since then, new articles have been placed on the web every three months and a number of the original articles have been updated. This process is continuing. The overall title has been changed to the Encyclopedia of Magnetic Resonance to allow for future articles on EPR and to accommodate the sensitivities of medical applications.

The existence of this large number of articles, written by experts in various fields, is enabling a new concept to be implemented, namely the publication of a series of printed handbooks on specific areas of NMR and MRI. The chapters of each of these handbooks will comprise a carefully chosen selection of Encyclopedia articles relevant to the area in question. In consultation with the Editorial Board, the handbooks are coherently planned in advance by specially selected editors. New articles are written and existing articles are updated to give appropriate complete coverage of the total area. The handbooks are intended to be of value and interest to research students, postdoctoral fellows, and other researchers learning about the topic in question and undertaking relevant experiments, whether in academia or industry.

Robin K. Harris

University of Durham, Durham, UK

Roderick E. Wasylishen

University of Alberta, Edmonton, Alberta, Canada

November 2009

Volume Preface

The RF coil is the component of the MRI system by which the MRI signal is stimulated and received or lost. Therefore informed specification, design, construction, evaluation, and application of properly selected RF coils are critical to a safe and successful MRI scan. Toward this goal, this handbook serves as an expository guide for engineers, scientists, medical physicists, radiographers, technologists, hands-on radiologists and other physicians, and for anyone with interests in building or selecting and using coils to achieve the best clinical or experimental results.

Since Purcell, Torrey, and Pound’s re-entrant cavity resonator and Bloch, Hansen, and Packard’s crossed transmit and receive coil pair (Physical Review, 1946), RF coils have evolved from the simple test-tube loaded, wire-wound solenoids and copper- tape resonators of chemistry laboratories to the complex multichannel transmitters and receivers of modern clinical and preclinical MRI systems. With deference to the literature already covering basic coil structures, this guide primarily addresses the dearth of reporting on modern coils for state-of-the-art MRI systems used in clinical diagnostics, biomedical research, and engineering R&D. Current RF coil designs and methods are covered across 33 chapters, divided into seven sections: surface coils, loop arrays, volume coils, special purpose coils, coil interface circuits, coil modeling and evaluation, and RF safety.

The first topic addressed is “surface coils,” which are loosely defined as coils placed adjacent to a surface of a region of interest (ROI) in an NMR- active sample such as human anatomy. A surface coil is used for localizing a near-surface ROI, with high transmit efficiency and/or receive sensitivity. The first two chapters introduce surface coils by their history of development, design, and application. Chapters 3–6 include designs for quadrature surface coils, double-tuned surface coils, nested multinuclear surface coils, and surface coils built of transmission line (TEM) elements.

A loop array might be regarded as an array of surface coils. There are surface arrays to be applied to surfaces, and volume arrays to subtend sample volumes. Developed initially as a means of efficiently transmitting to and receiving from larger ROIs with the sensitivity and efficiency of a surface coil, receive, transmit, and transceiver arrays of loops or transmission line elements have found new and more powerful applications in parallel imaging and parallel transmit schemes to further improve imaging speed, quality, and safety. To address this important topic, four chapters are included covering receiver loop arrays, array design for parallel imaging, transceiver loop arrays, and bench top characterization of multichannel coil arrays.

Volume coils, as their name suggests, encompass a sample volume. Common clinical examples are head, limb, and body coils. While there are a number of volume coil technologies by various names, two popular designs are the birdcage and TEM coils and their many variants. The birdcage was originally developed and used as a transceiver head and body coil. It continues to be the most widely used body coil in clinical systems today for exciting a uniform field over a large ROI in the body. Chapters 11 and 12 cover birdcage, and double-tuned birdcage volume coil design. The TEM coil is essentially an array of transmission line elements surrounding a volume, or adjacent to a surface. This structure preserves the inherent field uniformity of a birdcage, but gains the benefits of an array with independent element operation. Accordingly, it is a popular option for parallel-transceiver and parallel-transmit applications. Chapters 13–16 give examples of TEM volume coil designs. Chapter 17 extends the topic further with antenna array elements.

A wide variety of coils offering significant solutions to problems in clinical diagnosis and preclinical science but not neatly fitting into the above categories have been classified as “special purpose coils.”

Examples of five such coils are given in Chapters 18–22. Catheter coils for MRI-guided catheterization and high resolution vascular wall imaging is one example for clinical utility. Micro coils of sub-micrometer scale for nanoliter samples are an example of nanotechnology in coil design. Three popular approaches to preclinical probes are included with cryogenic and superconducting coils, single and double resonance litz probes, and millipede coils.

RF coils are of course not stand-alone devices. They must be designed within the context of the MRI system to which they interface. Receive coils must interface the system receiver(s). Transmit coils must interface the system power amplifier(s). Interfaces to the transmitter and receiver require close attention to impedance matching and baluns. The design, interface, and implementation of the receiver, transmitter, and impedance matching are covered in Chapters 23–25.

Coil design requires rigorous modeling and evaluation. The engineer must be familiar with these methods to design and build a safe and successful coil. Models are heavily relied upon by MRI technicians and physicians for predicting image quality and specific absorption rate (SAR) characteristics of a coil for a given application. This section lists six chapters dedicated to methods and examples of analytical and numerically based design and evaluation. A standard approach to RF coil analysis is given in Chapter 26. Chapter 27 reviews the analytical, finite difference time domain, finite element and moments methods of coil field modeling. Chapters 28–31 contribute specific examples of how to model fields and losses (SAR) for the birdcage and TEM coil designs.

The final section is reserved for the foremost concern for all coil designs and applications: “RF safety.” Chapter 32 reviews the current SAR-based safety standards by which safety practices and procedures for coil design and use are regulated. SAR and how to calculate SAR in the body with different coils and implants are explained. Tissue heating is demonstrated adjacent to implants and lead wires due to RF-E-field coupling. Chapter 33 addresses the primary safety concern, RF heating, through design and validation of a more accurate bioheat equation. The electrodynamics (SAR) as well as thermodynamics (perfusion and convective heat transfer) and physiology (thermoregulatory reflex) must all be considered for an accurate prediction of temperature contours in the MRI subject. Phantom, animal, and human experimental models are described for measuring systemic and local RF-induced temperature rise.

Thirty nine outstanding authors contributed 33 chapters for this handbook on RF Coils for MRI. Authors were invited by the editors to contribute RF designs or design methods for which they are best known; in many cases they are the inventors and leading innovators of their respective technologies. In an effort analogous to collecting recipes for a community cookbook, authors were asked to contribute an expository account of their favorite RF recipes. Emphasis on the materials and methods sections was requested. This was an opportunity for the senior experts to teach the next generation of coil builders and users how to design, build, and use their most effective designs. Tricks of the trade and other “proprietary” information were called for, information that could not be found in the sparse and disparate literature on these topics. With little more than copyediting, the results are before the readers in the authors’ own words. The personalities of the chapters therefore vary in style and content, but are preserved giving the reader an opportunity to meet the authors as well as to learn from them. Finally, Professor Vaughan wishes to thank his friend and colleague, Professor Griffiths whose steadfast patience, gentle prodding, and compensatory toil were necessary ingredients in baking this cake.

Above all else, we hope that engineers, scientists, technicians, and physicians will find “RF Coils for MRI” to be a useful addition to their laboratory benches and library shelves.

J. Thomas Vaughan

University of Minnesota, Minneapolis, Minnesota, USA

John R. Griffiths

Cancer Research UK, Cambridge Research Institute, Cambridge, UK

April 2012

PART A

Surface Coils

Chapter 1

An Historical Introduction to Surface Coils: The Early Days

Joseph J. H. Ackerman

Department of Chemistry, Campus Box 1134, Washington University, Saint Louis, MO 63130, USA

1.1 INTRODUCTION

Before the advent of modern magnetic resonance (MR) imaging scanners possessing superb magnetic-field-gradient systems and RF pulse shaping capabilities, it was common for objects that were to be examined by MR to be placed inside what are today known as RF volume transmit/receive coils. MR magnets “back in the day” had relatively narrow bores (few centimeters/inches) and similarly small samples, the most common sample-containing glass tube having an outer diameter of 5 mm. Small-diameter RF volume transmit/receive coils are highly sensitive on a per-unit-volume basis and provide quite homogeneous RF fields. The 5-mm MR probes now in use, common to all high-field, high-resolution analytical (structural chemistry/biology) magnetic resonance spectroscopy (MRS) systems, are highly evolved, offering extraordinary sensitivity, linewidth resolution, and multinuclide detection capabilities.

The introduction of larger bore superconducting magnets motivated the use of MRS for study of larger samples, in particular, intact biological systems, including small laboratory-animal models such as mice and rats. Volume coils had two disadvantages for studies such as these: they became increasingly insensitive with increasing sample size (receptivity scaling roughly as the inverse of the coil radius) and they offered no spatial selectivity (i.e., were unable to focus on a single organ or tissue of interest). Driven by a need for greater signal-to-noise sensitivity and spatial localization, surface coils were introduced, enabling numerous MRS studies of living systems and motivating additional engineering developments in concert with advances in magnet, magnetic-field-gradient, and RF technology.