Introduction to functional magnetic resonance imaging : principles and techniques

Half-title......Page 3
Title......Page 5
Copyright......Page 6
Dedication......Page 7
Contents......Page 9
Preface to the second edition......Page 11
Preface to the first edition......Page 13
Part I An overview of functional magnetic resonance imaging......Page 15
Part IA Introduction to the physiological basis of functional neuroimaging......Page 17
Metabolic activity accompanies neural activity......Page 19
Neural signaling......Page 21
Neural activity......Page 22
The membrane potential......Page 23
Synaptic activity......Page 24
Electrophysiology measurements......Page 26
Metabolism of ATP is required to restore ionic gradients following neural activity......Page 28
The sodium/potassium pump......Page 29
An ATP energy budget for neural activity......Page 30
Glycolysis in the cytosol......Page 32
Mitochondrial pyruvate metabolism and the electron transfer chain......Page 34
Delivery of glucose and O2 by blood flow......Page 36
Measuring the cerebral metabolic rate for glucose......Page 37
Increased glucose metabolism is closely associated with functional activity......Page 38
Measuring cerebral blood flow and O2 metabolism......Page 39
Balance of blood flow, glucose metabolism and O2 use in the brain at rest and during activation......Page 40
References......Page 46
The vascular system......Page 48
Tissue perfusion......Page 50
The central volume principle......Page 51
Cerebral blood flow is a measure of delivery of arterial blood......Page 52
Blood flow is controlled by changing vascular resistance......Page 53
The relationship between blood volume and blood flow during activation......Page 54
The development of ideas about control of cerebral blood flow......Page 56
Smooth muscle relaxation......Page 57
Vasoactive agents......Page 58
The neurovascular unit......Page 62
The nitrous oxide technique......Page 63
Diffusible versus intravascular tracers......Page 64
Techniques using PET......Page 66
Blood flow and glucose metabolism increase with functional activity......Page 67
Oxygen metabolism increases less than blood flow......Page 68
Summary of physiological changes during brain activation......Page 69
References......Page 73
Part IB Introduction to functional magnetic resonance imaging......Page 79
Introduction......Page 81
The basic NMR experiment......Page 84
Precession......Page 85
Equilibrium magnetization......Page 87
The radiofrequency pulse......Page 88
The free induction decay signal......Page 89
The basic NMR experiment again......Page 91
Pulse sequence parameters and image contrast......Page 92
Gradient echo pulse sequence......Page 93
The decay T2*......Page 94
Spin echoes......Page 95
Spin echo pulse sequence......Page 96
Inversion recovery pulse sequence......Page 97
References......Page 98
Radiofrequency coils......Page 99
Magnetic field gradients and gradient echoes......Page 100
Localization......Page 102
Slice selection......Page 103
Phase encoding......Page 104
k-Space......Page 105
Fast imaging......Page 106
Volume imaging......Page 108
Magnetic resonance angiography......Page 109
Diffusion-weighted imaging......Page 111
Magnetic susceptibility effects......Page 112
References......Page 114
Blood velocity effects......Page 115
Deoxyhemoglobin effects......Page 116
Cerebral blood flow measurement......Page 117
Alteration of local relaxation times......Page 118
Signal fall with contrast agent in the vasculature......Page 119
Imaging cerebral blood flow......Page 121
Principles of arterial spin labeling......Page 122
Blood susceptibility depends on deoxyhemoglobin content......Page 124
Mapping brain activation......Page 125
References......Page 128
Part II Principles of Magnetic resonance imaging......Page 131
Part IIA The nature of the magnetic resonance signal......Page 133
Introduction......Page 135
The field concept......Page 136
Magnetic fields......Page 137
Induction and NMR signal detection......Page 139
Gradient and radiofrequency coils......Page 142
Interaction of a magnetic dipole with a magnetic field......Page 144
Relaxation......Page 145
Radiofrequency excitation......Page 148
Frequency selective radiofrequency pulses: slice selection......Page 150
Adiabatic radiofrequency pulses......Page 153
Paramagnetism, diamagnetism, and ferromagnetism......Page 154
Magnetic susceptibility......Page 156
Field distortions in the head......Page 158
References......Page 159
Introduction......Page 161
Spin echoes......Page 162
Image contrast......Page 164
Stimulated echoes......Page 170
Multiple echo pathways from a string of radiofrequency pulses......Page 172
Gradient echoes......Page 173
Decay constant T2* and chemical shift effects......Page 174
Controlling T1 weighting with the flip angle......Page 176
Steady-state free precession......Page 177
The varieties of gradient echo pulse sequences......Page 179
Fluctuating fields......Page 180
A simple model for transverse relaxation......Page 181
The difference between longitudinal and transverse relaxation rates......Page 182
Contrast agents......Page 184
References......Page 186
Introduction......Page 187
The nature of diffusion......Page 188
Diffusion in a linear field gradient......Page 189
Techniques for diffusion imaging......Page 193
Multicompartment diffusion......Page 194
Restricted diffusion......Page 196
Diffusion imaging in stroke......Page 197
Anisotropic diffusion......Page 198
The diffusion tensor......Page 202
Measuring the trace of the diffusion tensor......Page 203
Fiber tract mapping......Page 206
Limitations of the diffusion tensor model......Page 207
Beyond the diffusion tensor model......Page 208
Diffusion around field perturbations......Page 210
Motional narrowing......Page 212
References......Page 214
Part IIB Magnetic resonance imaging......Page 217
Introduction......Page 219
Magnetic field gradients......Page 221
Gradient echoes......Page 222
The Fourier transform and k-space......Page 223
The net MR signal traces out the Fourier transform of the image......Page 225
Imaging as a snapshot of the transverse magnetization......Page 226
Phase encoding......Page 228
Mapping k-space......Page 230
Image field of view......Page 233
Image resolution......Page 234
Pixels, voxels, and resolution elements......Page 236
The point spread function......Page 237
A more general definition of resolution......Page 240
Gibbs artifact......Page 243
References......Page 245
Introduction......Page 254
Spin echo......Page 255
Asymmetric spin echo......Page 256
Gradient echo......Page 258
Echo-shifted pulse sequences......Page 260
Volume imaging......Page 262
Exploiting symmetries of k-space......Page 263
k-Space sampling trajectories for fast imaging......Page 264
Echo planar imaging......Page 265
Safety issues......Page 271
References......Page 272
Image signal to noise ratio......Page 274
Noise distribution......Page 277
Spatial smoothing......Page 279
Spatial correlations in noise......Page 280
Smoothing compared with reduced resolution acquisitions......Page 281
Ghost images in echo planar imaging......Page 283
Effects of T2* on image quality......Page 284
Image distortions from off-resonance effects......Page 287
Motion artifacts......Page 292
Physiological noise......Page 295
References......Page 297
Part III Principles of functional magnetic resonance imaging......Page 299
Part IIIA Perfusion imaging......Page 301
Perfusion imaging......Page 303
The beginning of fMRI......Page 304
Time–activity curves......Page 305
Volume of distribution of the agent......Page 306
A simple example......Page 307
Measuring cerebral blood flow and volume......Page 309
The general form of the tissue concentration–time curve......Page 310
The residue function......Page 314
Sensitivity of the tissue concentration–time curve to local blood flow and the volume of distribution......Page 316
The bolus tracking experiment......Page 318
Relating MR signal changes to agent concentration......Page 319
Recirculation of the agent......Page 320
The mean transit time......Page 321
Estimating cerebral blood flow from bolus tracking data......Page 322
Other contrast agent methods......Page 324
References......Page 325
Introduction......Page 329
The basic experiment......Page 330
Continuous arterial spin labeling......Page 335
Pulsed arterial spin labeling......Page 337
The importance of creating a well-defined arterial bolus......Page 340
Sources of systematic errors......Page 342
Controlling for transit delay effects......Page 344
Relaxation effects......Page 348
Absolute cerebral blood flow calibration......Page 350
Tagged water in arteries......Page 351
Recent innovations......Page 352
Activation studies with arterial spin labeling......Page 354
Simultaneous cerebral blood flow and O2 imaging......Page 355
The calibrated-BOLD method......Page 356
References......Page 357
Part IIIB Blood oxygenation level dependent imaging......Page 361
The discovery of the BOLD effect......Page 363
Magnetic field distortions shorten T2*......Page 364
Field distortions around a magnetized cylinder......Page 370
The moderating effect of diffusion on T2* changes......Page 372
The intravascular contribution to the BOLD signal......Page 374
Spin echo BOLD signal changes......Page 375
What does the BOLD response measure?......Page 377
The calibrated-BOLD method......Page 379
Magnetic field dependence......Page 380
Image acquisition parameters......Page 381
Motion artifacts......Page 384
Image distortions......Page 385
References......Page 387
Introduction to statistical analysis of BOLD data......Page 390
Separating true activations from noise......Page 391
The t-test......Page 393
Correlation analysis......Page 394
Fourier analysis......Page 395
The Kolmogorov–Smirnov test......Page 396
Noise correlations......Page 397
The general linear model......Page 398
The hemodynamic response......Page 399
Fitting the data with a known model response......Page 400
Statistical significance......Page 402
Fitting the data with a more general linear model......Page 403
The variance of the parameter estimates......Page 407
Statistical significance revisited......Page 410
Block designs and event-related designs......Page 411
Detection power for a known hemodynamic response......Page 413
Estimating an unknown hemodynamic response......Page 416
Detecting an unknown hemodynamic response......Page 418
Detection and estimation sensitivity......Page 419
References......Page 420
Introduction......Page 422
The basic BOLD measurement......Page 423
Understanding the BOLD response......Page 424
Physiological baseline effects......Page 425
Variability in coupling of cerebral blood flow and O2 metabolism......Page 427
Location of BOLD signal changes......Page 428
The relationship between the BOLD response and neural activity......Page 430
Linearity of the BOLD response......Page 431
Mapping resting state networks with spontaneous BOLD correlations......Page 432
The time scale of BOLD dynamics......Page 433
Transients of the BOLD response......Page 434
Interpreting the BOLD response in disease......Page 440
References......Page 441
The field of a magnetic dipole......Page 447
Interactions of a dipole with an external field......Page 448
Equilibrium magnetization......Page 449
Precession......Page 450
The quantum physics view of NMR......Page 451
Quantum effects......Page 452
The rules of quantum mechanics......Page 455
Macroscopic measurements......Page 459
Reference......Page 461
Index......Page 462