Essentials of Ultrasound Imaging,

1. Introduction 1
1.1 Overview 1
1.1.1 Prelude 1
1.1.2 In this chapter you will learn 2
1.2 Waves 2
1.3 Your very own imaging system 4
1.3.1 Electromagnetic spectrum 4
1.3.2 Digital camera imaging system 4
1.3.3 Our analog imaging system 6
1.4 Simulators 7
1.4.1 Introduction to simulators 7
1.4.2 First example of a simulator 8
1.5 Imaging up and down the electromagnetic spectrum 10
1.5.1 Imaging scorecard 10
1.5.2 Down the imaging electromagnetic spectrum 12
1.5.3 Up the imaging electromagnetic spectrum 14
1.5.4 Magnetic resonance imaging 15
1.5.5 Ultrasound imaging 16
1.5.6 Imaging modalities compared 17
1.6 Ultrasound imaging basics 19
1.6.1 A-line pulseecho system 19
1.6.2 Ultrasound imaging system 20
1.7 Imaging three-dimensional objects 21
1.7.1 Imaging modes 21
1.7.2 Three-dimensional imaging modes simulator 22
1.8 Ultrasound imaging systems 23
1.8.1 Ultrasound imaging system block diagram 23
1.8.2 Introduction to the Verasonics Vantage Research Ultrasound System 24
1.8.3 Imaging with the Vantage system 28
1.9 Lab 1: Two-dimensional imaging in a three-dimensional world 29
1.9.1 Exercises with simulator applications 30
1.9.2 Experiments and exercises with the Vantage system 32
References 35
2. Rays and waves 37
2.1 Overview 37
2.1.1 Introduction 37
2.1.2 Pulse Delay Simulator 38
2.1.3 In this chapter you will learn 39
2.2 Acoustic/electric analogs 39
2.3 Types of waves 42
2.3.1 Types of propagating wavefronts and the Expanding Waves Simulator 42
2.3.2 k-Rays 43
2.3.3 Elastic waves and the Elastic Wave Simulator 44
2.4 Oblique waves at a boundary 46
2.4.1 Waves at a boundary 46
2.4.2 Refraction at a boundary 47
2.4.3 Oblique reflection and transmission at a boundary 48
2.4.4 Oblique simulator 49
2.5 Pulses reverberating in layers 50
2.5.1 Reverberations in a layer 50
2.5.2 Layer Pulse Simulator 51
2.6 Waves in layers 52
2.6.1 Continuous waves in a layer 52
2.6.2 Continuous Wave Layer Simulator 54
2.7 Lab 2: reflection and refraction of acoustic waves 55
2.7.1 Physics simulator applications 55
2.7.2 Lab 2 learning objectives 55
2.7.3 Lab 2 description of exercises and illustrative results 56
References 59
3. Signals 61
3.1 Overview 61
3.1.1 Play with blocks 61
3.1.2 In this chapter you will learn 62
3.2 Fourier transforms link time waveforms and frequency spectra 62
3.2.1 Fourier Transform Simulator 62
3.2.2 Hilbert transform and pulse envelope 64
3.3 Blocks and filters 65
3.3.1 Combining blocks 65
3.3.2 Fourier Filter Simulator 65
3.4 ABCD matrices 66
3.4.1 ABCD block 66
3.4.2 Cascaded ABCD blocks 68
3.4.3 ABCD Simulator 68
3.5 Absorption 69
3.5.1 Power law absorption in the frequency domain 69
3.5.2 Absorption in the time domain 71
3.5.3 Absorption Filter Simulator 72
3.6 Lab 3: exploration of signals, filters networks and imaging of thin materials 74
3.6.1 Signal exercises with simulator applications 74
3.6.2 Experiments and exercises with the Vantaget system 75
References 78
4. Transducers 79
4.1 Overview 79
4.1.1 Transducer: the most critical part of an ultrasound system 79
4.1.2 In this chapter you will learn 79
4.2 Introduction to transducers and equivalent circuits 79
4.2.1 What is a transducer? 79
4.2.2 Three-port transducer model 83
4.2.3 Transducer blocks 84
4.2.4 Electrical transducer port 85
4.2.5 Transducer Simulator 86
4.2.6 Acoustical loss 87
4.2.7 Electrical loss 88
4.2.8 Insertion Loss 91
4.2.9 Transducer design 92
4.2.10 Transducer applications 94
4.3 Lab 4: exploring transducer modeling and the acoustic stack 95
4.3.1 Concepts explored with simulator applications 95
4.3.2 Experiments and exercises with the Vantage system 96
References 97
5. Beams and focusing 99
5.1 Overview 99
5.1.1 Diffraction 99
5.1.2 How beams are formed 100
5.1.3 In this chapter you will learn 102
5.2 Diffraction models for calculating beams 102
5.2.1 Spatial transforms 102
5.2.2 Beamplot Simulator 106
5.2.3 Rayleigh integral model 107
5.3 Field Simulator 113
5.3.1 Field Simulator control panel 113
5.3.2 Beamplot focusing characteristics 114
5.3.3 Axial focusing characteristics 116
5.4 Lab 5: beams and focusing and the point spread function 120
5.4.1 Exercises with the physics simulators 120
5.4.2 Experiments and exercises with the Vantaget system 122
References 123
6. Continuous wave array beamforming and heating 125
6.1 Overview 125
6.1.1 Beamformers in the block diagram 125
6.1.2 Array beamforming 125
6.1.3 Wavefronts Simulator 125
6.1.4 In this chapter you will learn 127
6.2 Imperfect element samplers 128
6.2.1 Rectangular array elements 128
6.2.2 Sampling by elements 131
6.3 Array directivity 132
6.3.1 Array and element factors 132
6.3.2 Directivity Simulator 133
6.4 Three-dimensional continuous wave array focusing and steering 134
6.4.1 Three-dimensional beam visualization 134
6.4.2 Continuous Wave Array Simulator for 3D beams 135
6.5 Absorbing media 137
6.5.1 Array focusing in absorbing media 137
6.5.2 Heating in absorbing media 137
6.5.3 Simulation of focusing and heating in absorbing media 138
6.6 Plane wave compounding 139
6.6.1 Principles of plane wave compounding 139
6.6.2 Plane Wave Compounding Simulator 140
6.7 Lab 6: exploring arrays and continuous wave beams in absorbing media 141
6.7.1 Exercises with the simulators 141
6.7.2 Experiments and exercises with the Vantage system 142
References 145
7. Pulsed phased array beamforming 147
7.1 Overview 147
7.1.1 Pulsed arrays 147
7.1.2 Wavefront animation simulations 148
7.1.3 In this chapter you will learn 150
7.2 How phased arrays form beams 151
7.2.1 Pulsed array principles 151
7.2.2 Pulsed Array Simulator 153
7.3 Effects of pulses and absorption on beams 154
7.3.1 Array drive pulse effects on beamshape 154
7.3.2 Absorption effects on beamshape 155
7.4 Pulsed grating lobes 155
7.4.1 Undersampling 155
7.4.2 Steering 157
7.5 Combined receive and transmit beamforming 159
7.5.1 Array receive focusing 159
7.5.2 Array round trip responses 161
7.5.3 Dynamic receive focusing—sensitivity to sound speed 163
7.6 Types of arrays 164
7.6.1 Types of scanning 164
7.6.2 Two-dimensional arrays 166
7.7 Lab 7: Pulsed array investigations 167
7.7.1 Experiments and exercises with the simulator 168
7.7.2 Experiments and exercises with the Vantage system 168
References 173
8. Ultrasound imaging systems and display 175
8.1 Overview 175
8.1.1 Block diagram 175
8.1.2 Back end processing 176
8.1.3 In this chapter you will learn 177
8.2 Image formation 177
8.2.1 Scanning and image formats 177
8.2.2 Image frame construction 178
8.2.3 A matrix of pixels 179
8.3 Acoustic line adventures 180
8.3.1 Point spread function ellipsoid revisited 180
8.3.2 Formation of an acoustic line 182
8.4 Imaging point targets 185
8.4.1 Wire targets 185
8.4.2 Scatter image simulator 186
8.4.3 MultiFocus simulator 187
8.5 Time gain compensation 190
8.5.1 Time gain compensation amplifiers 190
8.5.2 Attenuation compensation 191
8.5.3 Time gain compensation simulator 191
8.6 Scattering 192
8.6.1 Types of scattering 192
8.6.2 Speckle 194
8.6.3 Speckle simulator 195
8.7 Image contrast 196
8.7.1 Contrast resolution 196
8.7.2 Contrast measurement 197
8.8 Ultrasound video 199
8.8.1 Delay and sum approach 199
8.8.2 Plane wave compounding approach 199
8.8.3 Ultrasound video simulator 200
8.8.4 Bewildering ultrasound video artifacts 200
8.9 Lab 8: exploring ultrasound images and videos 201
8.9.1 Exercises with simulators 201
8.9.2 Experiments and exercises with the Vantage system 203
References 207
9. Doppler 209
9.1 Overview 209
9.1.1 The block diagram revisited 209
9.1.2 The Doppler effect 210
9.1.3 In This Chapter You Will Learn 212
9.2 Principles of Doppler Ultrasound Measurement of Flow 212
9.3 Continuous wave Doppler 214
9.4 Pulsed wave Doppler and Doppler processing 215
9.4.1 Pulsed wave Doppler 215
9.4.2 Pulsed wave Doppler processing and display 216
9.5 Color flow and power Doppler imaging 221
9.6 Power Doppler imaging 223
9.7 Ultrafast Doppler imaging 225
9.8 Vector Doppler imaging 226
9.8.1 Motivation 226
9.8.2 Combining Doppler information from multiple directions 227
9.8.3 Vector Doppler using ultrafast plane waves from a single direction 230
9.9 The Vantaget Doppler simulation using moving point scatterers 231
9.9.1 The flow model 231
9.9.2 Vantage Doppler imaging sequence using plane waves 233
9.9.3 The Color Flow Doppler Simulator 236
9.10 Lab 9: numerically simulated Doppler imaging 237
9.10.1 Introduction 237
9.10.2 Exercises using the Vantage Doppler simulation tool 238
References 240
10. Advanced ultrasound imaging systems and topics 243
10.1 Overview 243
10.1.1 Two views of ultrasound 243
10.1.2 In this chapter you will learn 245
10.2 Ultrasound imaging and research systems 246
10.2.1 Ultrasound imaging commercial systems 246
10.2.2 Ultrasound imaging research systems 247
10.2.3 Comparison of ultrasound imaging systems 252
10.3 Acoustic nolinearity and harmonic imaging 254
10.4 Ultrasound contrast agents 257
10.4.1 Bubbles as nonlinear resonators 257
10.4.2 Clinical applications of contrast agents 258
10.5 Elastography imaging 261
10.5.1 Strain elastography imaging 261
10.5.2 Shear wave elastography imaging 261
10.6 Three-dimensional imaging 265
10.7 High-frequency imaging 267
10.8 Photoacoustics 268
10.9 High-intensity focused ultrasound 270
10.10 Neuromodulation 273
10.11 Microvascular imaging and super-resolution 275
10.12 Functional ultrasound 277
10.13 Material science: nondestructive evaluation/nondestructive testing 279
10.14 Underwater acoustics and SONAR 280
10.15 Conclusion 282
References 284
Further reading 287
Appendix A: ultrasound resources 289
Appendix B 291
Appendix C: IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society Terminology 297
Appendix D: Table of material properties 301
Index 303