Introduction to Diffusion Tensor Imaging

Front cover......Page 1
Introduction to Diffusion Tensor Imaging......Page 4
Copyrightpage......Page 5
Contents......Page 6
Preface......Page 10
ACKNOWLEDGEMENTS......Page 14
1.1 NMR SPECTROSCOPYANDMRI CAN DETECT SIGNALS FROM WATER MOLECULES......Page 16
1.2 WHAT IS DIFFUSION?......Page 18
1.3 HOW TO MEASURE DIFFUSION?......Page 19
2.2 THERE ARE FOUR PARAMETERS THAT AFFECT THE AMOUNT OF SIGNAL LOSS......Page 28
2.3 THERE ARE SEVERAL WAYS OF ACHIEVING A DIFFERENT DEGREE OF DIFFUSION WEIGHTING......Page 32
3.1 WE NEED TO CALCULATE DISTRIBUTION OF SIGNAL PHASES BY MOLECULAR MOTION......Page 34
3.3 DIFFUSION CONSTANT CAN BE OBTAINED FROM THE AMOUNT OF SIGNAL LOSS BUT NOT FROM THE SIGNAL INTENSITY......Page 42
3.4 FROM TWO MEASUREMENTS, WE CAN OBTAIN A DIFFUSION CONSTANT......Page 45
3.5 IF THERE ARE MORE THAN TWO MEASUREMENT POINTS, LINEAR LEAST-SQUARE FITTING IS USED......Page 46
4.2 DIFFUSION SOMETIMES HAS DIRECTIONALITY......Page 48
4.3 SIX PARAMETERS ARE NEEDED TO UNIQUELY DEFINE AN ELLIPSOID......Page 50
4.4 DIFFUSION TENSOR IMAGING CHARACTERIZES THE DIFFUSION ELLIPSOID FROM MULTIPLE DIFFUSION CONSTANT MEASUREMENTS ALONG DIFFERENT DIRECTIONS......Page 52
4.5 WATER MOLECULES PROBE MICROSCOPIC PROPERTIES OF THEIR ENVIRONMENT......Page 54
4.6 HUMAN BRAIN WHITE MATTER HAS HIGH DIFFUSION ANISOTROPY......Page 55
5.1 OUR TASK IS TO DETERMINE THE SIX PARAMETERS OF A DIFFUSION ELLIPSOID......Page 56
5.2 WE CAN OBTAIN THE SIX PARAMETERS FROM SEVEN DIFFUSION MEASUREMENTS......Page 58
5.3 DETERMINATION OF THE TENSOR ELEMENTS FROM A FITTING PROCESS......Page 60
6.1 TWO TYPES OF MOTION ARTIFACTS: GHOSTING AND COREGISTRATION ERROR......Page 64
6.2 WE USE ECHO-PLANAR IMAGING TO PERFORM DIFFUSION TENSOR IMAGING......Page 66
6.4 THERE ARE VARIOUS k-SPACE SAMPLING SCHEMES......Page 68
6.5 PARALLEL IMAGING IS GOOD NEWS FOR DTI......Page 72
6.6 IMAGE DISTORTION BY EDDY CURRENT NEEDS SPECIAL ATTENTION......Page 75
6.7 DTI RESULTS MAY DIFFER IF SPATIAL RESOLUTION AND SNR ARE NOT THE SAME......Page 76
6.8 SELECTION OF b-MATRIX......Page 78
7.1 TWO SCALAR MAPS (ANISOTROPY AND DIFFUSION CONSTANT MAPS) AND FIBER ORIENTATION MAPS ARE IMPORTANT OUTCOMES OBTAINED FROM DTI......Page 84
7.2 SCALAR MAPS (ANISOTROPY AND DIFFUSION CONSTANT MAPS) AND FIBER ORIENTATION MAPS ARE TWO IMPORTANT IMAGES OBTAINED FROM DTI......Page 85
7.3 THERE ARE TUBULAR AND PLANAR TYPES OF ANISOTROPY......Page 87
7.4 DTI HAS SEVERAL DISADVANTAGES......Page 90
7.5 THERE ARE MULTIPLE SOURCES THAT DECREASE ANISOTROPY......Page 91
7.6 ANISOTROPY MAY PROVIDE UNIQUE INFORMATION......Page 94
7.7 COLOR-CODEDMAPS ARE A POWERFUL VISUALIZATION METHOD TO REVEAL WHITE MATTER ANATOMY......Page 98
8.1 TENSORMODEL OVERSIMPLIFIES THE UNDERLYING ANATOMY......Page 100
8.2 THERE ARE MORE SOPHISTICATED ‘‘NON-TENSOR”-BASED DATA PROCESSING METHODS, WHICH REQUIRE DIFFERENT DATA ACQUISITION PROTOCOLS......Page 102
8.3 NON-TENSOR MODELS USUALLY REQUIRE HIGH VALUES......Page 105
9.2 THERE ARE TWO TYPES OF RECONSTRUCTION TECHNIQUES......Page 108
9.3 THERE ARE THREE STEPS IN THE TRACT PROPAGATION MODELS......Page 109
9.4 SIMPLE STREAMLINE TRACKING CAN BE USED TO RECONSTRUCT A TRACT......Page 110
9.5 THERE ARE MANY LIMITATIONS TO SIMPLE TRACT PROPAGATION METHODS......Page 114
9.6 SEVERAL APPROACHES ARE PROPOSED TO TACKLE THE LIMITATIONS......Page 115
9.7 TRACT EDITING USESMULTIPLE REGIONS OF INTEREST......Page 121
9.9 ACCURACY AND PRECISION ARE IMPORTANT FACTORS TO BE CONSIDERED......Page 125
9.10 REPRODUCIBILITY OF TRACTOGRAPHY IS MEASURABLE......Page 128
9.11 TRACTOGRAPHY REVEALS MACROSCOPIC WHITE MATTER ANATOMY......Page 129
9.12 THERE ARE ROUGHLY THREE TYPES OF INFORMATION OBTAINED FROM TRACTOGRAPHY......Page 130
9.13 HOWCAN WEVALIDATE TRACTOGRAPHY?......Page 132
9.14 HOW SHOULD WE USE A TOOL WITH UNKNOWN ACCURACY?......Page 134
9.15 QUANTIFICATION IS A KEY TO MANY TYPES OF TRACTOGRAPHY-BASED STUDIES......Page 135
9.16 THERE ARE SEVERAL POSSIBLE REASONS THAT LEAD TO SMALLER (OR LARGER) RECONSTRUCTION RESULTS......Page 136
10.1 IMPROVEMENT OF CONVENTIONAL QUANTIFICATION APPROACHES......Page 140
10.2 QUANTIFICATION OF ANISOTROPY AND TRACT SIZES BY DTI......Page 145
11.1 BACKGROUND OF APPLICATION STUDIES OF DTI......Page 164
11.2 EXAMPLES OF APPLICATION STUDIES......Page 165
PREFACE......Page 178
CHAPTER 4......Page 179
CHAPTER 6......Page 180
CHAPTER 7......Page 181
CHAPTER 9......Page 183
CHAPTER 10......Page 185
CHAPTER 11......Page 186
Subject Index......Page 190