DONALD W. MCROBBIE has more than thirty years' experience in MRI safety. He is currently Adjunct Associate Professor, Discipline of Medical Physics in the School of Physical Sciences at the University of Adelaide, Adelaide, Australia.

Foreword ix

Acknowledgments xi

Chapter 1 Systems and safety: MR hardware and fields 1

Introduction 1

Overview of MRI operation 3

MRI hardware 10

Electromagnetic fields 16

Other medical devices 24

Conclusions 25

Chapter 2 Let's get physical: fields and forces 27

Basic laws of magnetism 27

Magnetic materials 32

Forces and torque 39

Lorentz and hydrodynamic forces 50

Laws of induction 51

Conclusions 57

Chapter 3 Biöeffects 1: static field 61

Introduction 61

Physical mechanisms 61

Cellular effects 67

Animal effects 69

Human physiological effects 70

Acute sensory effects 70

Epidemiology 70

Cognitive effects 74

Static field exposure limits 74

Conclusions 74

Chapter 4 Biöeffects 2: time¿varying gradient fields 79

Introduction 79

Physical interaction 79

ELF time¿varying magnetic field effects 83

Magnetic stimulation 86

Peripheral nerve stimulation in MRI 96

Exposure limits 99

Conclusions 102

Chapter 5 Biöeffects 3: radiöfrequency fields 107

Introduction 107

Physical interaction 107

Tissue heating 112

Biological effects 118

RF exposure limits 124

Controlling SAR in practice 127

Conclusions 132

Chapter 6 Acoustic noise 137

Introduction 137

Generation of acoustic noise in MRI 137

Measuring noise: dB(A), dB(C), dB(Z) 138

Anatomy and physiology of human hearing 143

MRI noise exposure 146

Reducing acoustic noise in practice 150

Hearing protection 151

Acoustic noise limits 155

Conclusions 158

Chapter 7 Pregnancy 161

Introduction 161

Cellular effects and animal studies 161

Human studies and epidemiology 162

Gadolinium¿based contrast agents 164

Exposure limits and guidance 166

Conclusions 169

Chapter 8 Contrast agents 173

Introduction 173

Physical and chemical properties 173

Contrast reactions and adverse events 180

Pregnancy and lactation 186

Conclusions 186

Chapter 9 Passive implants 191

Introduction 191

Risks from passive implants 191

ASTM testing 209

Examples of passive implants 214

Artefacts 218

Conclusions 221

Chapter 10 Active implants 227

Introduction 227

Risks from active implants 227

Pacemakers and ICDs 236

Neurostimulators 243

Cochlear implants 249

Endoscopic cameras 253

Implantable infusion pumps 253

Keeping within the conditions 255

Conclusions 257

Chapter 11 Would you scan this? Understanding the conditions 263

Introduction 263

MRI conditions 263

Understanding fringe field spatial gradient maps 265

Understanding RF conditions 275

Gradient slew rate condition 278

More examples 279

Off¿label scanning 281

What to do when you do not know the conditions? 281

Conclusions 285

Chapter 12 Location, location, location: suite design 289

Introduction 289

ACR zoning scheme 289

Fringe field 292

Helium exhaust and quench pipe 292

Security 296

Safety features 297

MRI project management 301

Specialist systems 302

Conclusions 303

Chapter 13 But what about us? Occupational exposure 307

Introduction 307

Occupational exposure limits 307

National and international limits 308

Surveys of occupational exposure levels 313

Survey instrumentation 317

Incidence of biöeffects among magnet facility and MR workers 317

Conclusions 317

Chapter 14 Organisation and management 321

Introduction 321

Roles in MR safety 321

Policy and safety documentation 324

Checklist and screening 326

Incidents 328

Emergencies 329

Training 330

Accreditation and certification 331

Standards and guidance 333

Exposure limits 337

Conclusions: the last word 337

Appendix 1 One hundred equations you need to know 341

Maxwell's equations 341

Magnetic field induction 342

Magnetic materials 345

Forces and torque 345

Forces on moving charges 350

Laws of induction 351

RF induction from the radiofrequency field 352

SAR and tissue heating 354

Appendix 2 Maths toolkit 357

Coordinate systems 357

Vector algebra 358

Vector calculus 360

Appendix 3 Symbols and constants 363

Answers to revision questions 367

Index 369