Foreword | p. vii |
Why This Book? | p. ix |
A User's Guide | p. xi |
Acknowledgments | p. xv |
In the Beginning: Generating, Detecting, and Manipulating the MR (NMR) Signal | |
Laying the Foundation: Nuclear Magnetism, Spin, and the NMR Phenomenon | p. 3 |
The Overall Aim | p. 3 |
Where Does the MRI Signal Come From? | p. 4 |
Interaction of Protons with a Static Magnetic Field (B) | p. 10 |
The Energy Configuration Approach: A Painless (Really!) Bit of Quantum Mechanics | p. 12 |
One More Thing ... What Exactly Is the MRI Signal That We Measure? | p. 18 |
Rocking the Boat: Resonance, Excitation, and Relaxation | p. 19 |
Introduction: How Can We Find a Signal to Measure? | p. 19 |
Generating Net Transverse Magnetization | p. 20 |
Relaxation: What Happens Next? | p. 27 |
What Happens When the Radiofrequency Is Shut Off? | p. 27 |
Separate, but Equal (Sort of): Two Components of Relaxation | p. 27 |
The Spin Echo | p. 32 |
Image Contrast: T1, T2, T2*, and Proton Density | p. 38 |
T2/T2* Contrast | p. 38 |
T1 Contrast | p. 40 |
Proton Density Contrast | p. 44 |
Putting Things Together to Control Image Contrast | p. 45 |
Hardware, Especially Gradient Magnetic Fields | p. 47 |
Why This Chapter? | p. 47 |
The B[subscript 0] Magnetic Field | p. 47 |
Radiofrequency Transmission | p. 55 |
The Gradient Magnetic Field | p. 55 |
The RF Coils | p. 60 |
The Receiver (A2D) | p. 65 |
The Computer | p. 66 |
Shielding | p. 68 |
The Prescan Process | p. 71 |
User Friendly: Localizing and Optimizing the MRI Signal for Imaging | |
Spatial Localization: Creating an Image | p. 75 |
What Is an Image? | p. 75 |
Understanding and Exploiting B[subscript 0] Homogeneity | p. 77 |
Slice Selection Using the Gradient Magnetic Field | p. 78 |
Localizing Signal Within the Plane of the Slice: Background for Frequency and Phase Encoding | p. 82 |
Frequency Encoding: The Next Stage | p. 84 |
Phase Encoding and the Two-dimensional Fourier Transform | p. 90 |
Some Comments Regarding k-Space | p. 97 |
Defining Image Size and Spatial Resolution | p. 101 |
How Much Area Will Be Included in the Image? | p. 101 |
Specifying the Field of View | p. 102 |
Aliasing and Its Fixes | p. 103 |
Refining the Field of View | p. 107 |
A Footnote Regarding Receiver Bandwidth | p. 109 |
Putting It All Together: An Introduction to Pulse Sequences | p. 110 |
Putting It All Together | p. 110 |
What Exactly Is a Pulse Sequence? | p. 110 |
The Pulse Sequence Diagram | p. 111 |
Building the Pulse Sequence | p. 113 |
The Spin Echo Pulse Sequence: A First Example | p. 113 |
What Happens After TE: Multiple Echoes and Multiple Slices | p. 116 |
The Gradient Echo Pulse Sequence | p. 119 |
Contrast Modification in SE and GRE Imaging | p. 127 |
Understanding, Assessing, and Maximizing Image Quality | p. 128 |
What Is the Measure of a Good Image? | p. 128 |
What Is Noise? | p. 129 |
Signal-to-Noise Ratio: Measuring Image Quality | p. 129 |
What Affects Signal to Noise? | p. 131 |
Contrast-to-Noise Ratio: Measuring Diagnostic Utility | p. 134 |
Quality Assurance | p. 135 |
Artifacts: When Things Go Wrong, It's Not Necessarily All Bad | p. 139 |
Things Do Go Wrong ... but It's Not All Bad News | p. 139 |
Motion | p. 139 |
Undersampling (Wraparound Artifact) | p. 141 |
Susceptibility Effects: Signal Loss and Geometric Distortion | p. 144 |
Truncation (Gibbs Artifact) | p. 146 |
Radiofrequency Leak (Zipper Artifact) | p. 149 |
k-Space Corruption: (Corduroy, Herringbone, and Spike Artifacts) | p. 150 |
Chemical Shift Artifact | p. 151 |
Slice Profile Interactions (Cross-Talk Artifact) | p. 153 |
Safety: First, Do No Harm | p. 154 |
Who Cares? | p. 154 |
The Safety of MRI Versus Iatrogenic Injury | p. 154 |
Types of MRI Risk | p. 155 |
Keeping It Safe: S[superscript 4] | p. 159 |
To the Limit: Advanced MRI Applications | |
Preparatory Modules: Saturation Techniques | p. 165 |
Inversion-Recovery Imaging | p. 165 |
Spectral Saturation Techniques | p. 169 |
Hybrid Techniques | p. 170 |
Selective Excitation | p. 170 |
Spatial Saturation | p. 171 |
Magnetization Transfer Contrast | p. 172 |
Readout Modules: Fast Imaging | p. 174 |
Gradient Echo Approaches | p. 174 |
Steady-State Free Precession | p. 177 |
Manipulating k-Space | p. 177 |
Hyperspace: Echoplanar Imaging | p. 182 |
Further Exploits in k-Space | p. 185 |
Volumetric Imaging: The Three-dimensional Fourier Transform | p. 187 |
Multislice Versus Volumetric Imaging: Three-dimensional Versus Two-dimensional | p. 187 |
Two-dimensional Imaging: How Do We Do It? | p. 187 |
Three-dimensional Imaging: How Do We Do It? | p. 188 |
Parallel Imaging: Acceleration with SENSE and SMASH | p. 194 |
Why Another Imaging Technique? | p. 194 |
So What's New? | p. 194 |
Basics of Parallel Techniques | p. 195 |
Sensitivity Encoding: SENSE | p. 197 |
Simultaneous Acquisition of Spatial Harmonics: SMASH | p. 198 |
What Do We Actually Gain and at What Cost? | p. 198 |
Flow and Angiography: Artifacts and Imaging of Coherent Motion | p. 200 |
What Is Magnetic Resonance Angiography Anyway? | p. 200 |
Basic Principles of Flow for Students of MRI | p. 201 |
Impact of Flow on the MR Signal | p. 203 |
Time-of-Flight MRA | p. 212 |
Something Different: Contrast-Enhanced MRA | p. 221 |
Don't Forget This Pitfall! | p. 225 |
Phase-Contrast MRA | p. 226 |
Where Do We Go from Here? | p. 232 |
Diffusion: Detection of Microscopic Motion | p. 233 |
Introduction | p. 233 |
What Is Diffusion? | p. 233 |
Effect of Diffusion on the MR Signal | p. 234 |
Making the MR Image Sensitive to Diffusion | p. 234 |
What Do Diffusion-Sensitized Images Look Like? | p. 236 |
Quantitative Diffusion Imaging: The ADC | p. 238 |
Directional Information: DTI | p. 239 |
Understanding and Exploiting Magnetic Susceptibility | p. 245 |
What Is Magnetic Susceptibility (x) Anyway? | p. 245 |
Proton-Electron Dipole Interactions: The Other Face of Paramagnetism | p. 248 |
Susceptibility-Related Effects I: Artifacts | p. 248 |
Susceptibility-Related Effects II: Hemorrhage | p. 249 |
Susceptibility-Related Effects III: Contrast Agents | p. 254 |
Susceptibility-Related Effects IV: Perfusion Imaging | p. 255 |
Susceptibility-Related Effects V: Functional MRI | p. 259 |
Spectroscopy and Spectroscopic Imaging: In Vivo Chemical Assays by Exploiting the Chemical Shift | p. 263 |
Introduction | p. 263 |
The Chemical Basis of MRS | p. 263 |
What Then Is Spectroscopy (MRS) and How Is It Different from MRI? | p. 264 |
Abundance, Resolution, and Detection | p. 265 |
The Importance of Field Homogeneity | p. 266 |
Localization: Single-Voxel Methods | p. 267 |
Localization: Chemical Shift Imaging | p. 270 |
Brain Chemistry: Brief Overview of the Proton Spectrum | p. 272 |
Appendices | |
Understanding and Manipulating Vectors | p. 277 |
Glossary of Terms | p. 279 |
Glossary of Common MRI Acronyms, Abbreviations, and Notations | p. 291 |
Resources for Reference and Further Study | p. 297 |
Index | p. 299 |
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