Essentials of Ultrasound Imaging

Essentials of Ultrasound Imaging offers a fast track introduction to the science, physics and technology of ultrasound imaging systems. Uniquely, principles are revealed by examples from software simulation programs, thus allowing the reader to engage with the concepts having minimal mathematical background. The material is organized around a functional block diagram which is, in turn, related to physical processes and implementations of the functional concepts on commercial and research imaging systems. Examples from a Verasonics Vantage Research Ultrasound System provide unparalleled insight into each step of ultrasound image creation including signal processing, transducer operation, different types of beamforming, and image formation. The last chapter examines the potential and capabilities of ultrasound imaging and measurement for future applications. With a thorough grounding of the physics and methods of ultrasound imaging, this book is suitable for students learning about ultrasound and researchers involved, or starting out in, ultrasound research development who might not have the background to understand the latest developments. Gives an understanding of wave propagation, piezoelectric transducers, beam focusing, Doppler imaging of fluid flow, types of ultrasound systems, and real-time image formation and resolutionExplains basic mathematical and scientific concepts underlying ultrasound imaging and physicsFollows the passage of pulse-echo waveforms through the changes made by wave propagation, array beam formation, absorption, and system processing to image formationDescribes the concepts written in MATLAB® that are illustrated by numerous examples from unique simulations of physics, processing, and imaging and from experiments and signals within an ultrasound research systemPresents an accompanying simulator software package, in executable form, designed to demonstrate concepts with minimal mathematical background, together with a curriculum of hands-on experiments using an ultrasound research system, both available from Verasonics Front Cover Essentials of Ultrasound Imaging Copyright Page Contents Preface Acknowledgments 1 Introduction 1.1 Overview 1.1.1 Prelude 1.1.2 In this chapter you will learn 1.2 Waves 1.3 Your very own imaging system 1.3.1 Electromagnetic spectrum 1.3.2 Digital camera imaging system 1.3.3 Our analog imaging system 1.4 Simulators 1.4.1 Introduction to simulators 1.4.2 First example of a simulator 1.5 Imaging up and down the electromagnetic spectrum 1.5.1 Imaging scorecard 1.5.2 Down the imaging electromagnetic spectrum 1.5.3 Up the imaging electromagnetic spectrum 1.5.4 Magnetic resonance imaging 1.5.5 Ultrasound imaging 1.5.6 Imaging modalities compared 1.6 Ultrasound imaging basics 1.6.1 A-line pulse–echo system 1.6.2 Ultrasound imaging system 1.7 Imaging three-dimensional objects 1.7.1 Imaging modes 1.7.2 Three-dimensional imaging modes simulator 1.8 Ultrasound imaging systems 1.8.1 Ultrasound imaging system block diagram 1.8.2 Introduction to the Verasonics Vantage Research Ultrasound System 1.8.3 Imaging with the Vantage system 1.9 Lab 1: Two-dimensional imaging in a three-dimensional world 1.9.1 Exercises with simulator applications 1.9.1.1 Secret Object Simulator 1.9.1.2 Imaging Systems Simulator 1.9.2 Experiments and exercises with the Vantage system References 2 Rays and waves 2.1 Overview 2.1.1 Introduction 2.1.2 Pulse Delay Simulator 2.1.3 In this chapter you will learn 2.2 Acoustic/electric analogs 2.3 Types of waves 2.3.1 Types of propagating wavefronts and the Expanding Waves Simulator 2.3.2 k-Rays 2.3.3 Elastic waves and the Elastic Wave Simulator 2.4 Oblique waves at a boundary 2.4.1 Waves at a boundary 2.4.2 Refraction at a boundary 2.4.3 Oblique reflection and transmission at a boundary 2.4.4 Oblique simulator 2.5 Pulses reverberating in layers 2.5.1 Reverberations in a layer 2.5.2 Layer Pulse Simulator 2.6 Waves in layers 2.6.1 Continuous waves in a layer 2.6.2 Continuous Wave Layer Simulator 2.7 Lab 2: reflection and refraction of acoustic waves 2.7.1 Physics simulator applications 2.7.2 Lab 2 learning objectives 2.7.3 Lab 2 description of exercises and illustrative results References 3 Signals 3.1 Overview 3.1.1 Play with blocks 3.1.2 In this chapter you will learn 3.2 Fourier transforms link time waveforms and frequency spectra 3.2.1 Fourier Transform Simulator 3.2.2 Hilbert transform and pulse envelope 3.3 Blocks and filters 3.3.1 Combining blocks 3.3.2 Fourier Filter Simulator 3.4 ABCD matrices 3.4.1 ABCD block 3.4.2 Cascaded ABCD blocks 3.4.3 ABCD Simulator 3.5 Absorption 3.5.1 Power law absorption in the frequency domain 3.5.2 Absorption in the time domain 3.5.3 Absorption Filter Simulator 3.6 Lab 3: exploration of signals, filters networks and imaging of thin materials 3.6.1 Signal exercises with simulator applications 3.6.2 Experiments and exercises with the VantageTM system References 4 Transducers 4.1 Overview 4.1.1 Transducer: the most critical part of an ultrasound system 4.1.2 In this chapter you will learn 4.2 Introduction to transducers and equivalent circuits 4.2.1 What is a transducer? 4.2.2 Three-port transducer model 4.2.3 Transducer blocks 4.2.4 Electrical transducer port 4.2.5 Transducer Simulator 4.2.6 Acoustical loss 4.2.7 Electrical loss 4.2.8 Insertion Loss 4.2.9 Transducer design 4.2.10 Transducer applications 4.3 Lab 4: exploring transducer modeling and the acoustic stack 4.3.1 Concepts explored with simulator applications 4.3.2 Experiments and exercises with the Vantage system References 5 Beams and focusing 5.1 Overview 5.1.1 Diffraction 5.1.2 How beams are formed 5.1.3 In this chapter you will learn 5.2 Diffraction models for calculating beams 5.2.1 Spatial transforms 5.2.2 Beamplot Simulator 5.2.3 Rayleigh integral model 5.3 Field Simulator 5.3.1 Field Simulator control panel 5.3.2 Beamplot focusing characteristics 5.3.3 Axial focusing characteristics 5.4 Lab 5: beams and focusing and the point spread function 5.4.1 Exercises with the physics simulators 5.4.2 Experiments and exercises with the VantageTM system References 6 Continuous wave array beamforming and heating 6.1 Overview 6.1.1 Beamformers in the block diagram 6.1.2 Array beamforming 6.1.3 Wavefronts Simulator 6.1.4 In this chapter you will learn 6.2 Imperfect element samplers 6.2.1 Rectangular array elements 6.2.2 Sampling by elements 6.3 Array directivity 6.3.1 Array and element factors 6.3.2 Directivity Simulator 6.4 Three-dimensional continuous wave array focusing and steering 6.4.1 Three-dimensional beam visualization 6.4.2 Continuous Wave Array Simulator for 3D beams 6.5 Absorbing media 6.5.1 Array focusing in absorbing media 6.5.2 Heating in absorbing media 6.5.3 Simulation of focusing and heating in absorbing media 6.6 Plane wave compounding 6.6.1 Principles of plane wave compounding 6.6.2 Plane Wave Compounding Simulator 6.7 Lab 6: exploring arrays and continuous wave beams in absorbing media 6.7.1 Exercises with the simulators 6.7.2 Experiments and exercises with the Vantage system References 7 Pulsed phased array beamforming 7.1 Overview 7.1.1 Pulsed arrays 7.1.2 Wavefront animation simulations 7.1.3 In this chapter you will learn 7.2 How phased arrays form beams 7.2.1 Pulsed array principles 7.2.2 Pulsed Array Simulator 7.3 Effects of pulses and absorption on beams 7.3.1 Array drive pulse effects on beamshape 7.3.2 Absorption effects on beamshape 7.4 Pulsed grating lobes 7.4.1 Undersampling 7.4.2 Steering 7.5 Combined receive and transmit beamforming 7.5.1 Array receive focusing 7.5.2 Array round trip responses 7.5.3 Dynamic receive focusing—sensitivity to sound speed 7.6 Types of arrays 7.6.1 Types of scanning 7.6.2 Two-dimensional arrays 7.7 Lab 7: Pulsed array investigations 7.7.1 Experiments and exercises with the simulator 7.7.2 Experiments and exercises with the Vantage system References 8 Ultrasound imaging systems and display 8.1 Overview 8.1.1 Block diagram 8.1.2 Back end processing 8.1.3 In this chapter you will learn 8.2 Image formation 8.2.1 Scanning and image formats 8.2.2 Image frame construction 8.2.3 A matrix of pixels 8.3 Acoustic line adventures 8.3.1 Point spread function ellipsoid revisited 8.3.2 Formation of an acoustic line 8.4 Imaging point targets 8.4.1 Wire targets 8.4.2 Scatter Image Simulator 8.4.3 MultiFocus Simulator 8.5 Time gain compensation 8.5.1 Time gain compensation amplifiers 8.5.2 Attenuation compensation 8.5.3 Time gain compensation simulator 8.6 Scattering 8.6.1 Types of scattering 8.6.2 Speckle 8.6.3 Speckle Simulator 8.7 Image contrast 8.7.1 Contrast resolution 8.7.2 Contrast measurement 8.8 Ultrasound video 8.8.1 Delay and sum approach 8.8.2 Plane wave compounding approach 8.8.3 Ultrasound Video Simulator 8.8.4 Bewildering ultrasound video artifacts 8.9 Lab 8: exploring ultrasound images and videos 8.9.1 Exercises with simulators 8.9.2 Experiments and exercises with the Vantage system References 9 Doppler 9.1 Overview 9.1.1 The block diagram revisited 9.1.2 The Doppler effect 9.1.3 In This Chapter You Will Learn 9.2 Principles of Doppler Ultrasound Measurement of Flow 9.3 Continuous wave Doppler 9.4 Pulsed wave Doppler and Doppler processing 9.4.1 Pulsed wave Doppler 9.4.2 Pulsed wave Doppler processing and display 9.5 Color flow and power Doppler imaging 9.6 Power Doppler imaging 9.7 Ultrafast Doppler imaging 9.8 Vector Doppler imaging 9.8.1 Motivation 9.8.2 Combining Doppler information from multiple directions 9.8.3 Vector Doppler using ultrafast plane waves from a single direction 9.9 The VantageTM Doppler simulation using moving point scatterers 9.9.1 The flow model 9.9.2 Vantage Doppler imaging sequence using plane waves 9.9.3 The Color Flow Doppler Simulator 9.10 Lab 9: numerically simulated Doppler imaging 9.10.1 Introduction 9.10.2 Exercises using the Vantage Doppler simulation tool References 10 Advanced ultrasound imaging systems and topics 10.1 Overview 10.1.1 Two views of ultrasound 10.1.2 In this chapter you will learn 10.2 Ultrasound imaging and research systems 10.2.1 Ultrasound imaging commercial systems 10.2.2 Ultrasound imaging research systems 10.2.3 Comparison of ultrasound imaging systems 10.3 Acoustic nolinearity and harmonic imaging 10.4 Ultrasound contrast agents 10.4.1 Bubbles as nonlinear resonators 10.4.2 Clinical applications of contrast agents 10.5 Elastography imaging 10.5.1 Strain elastography imaging 10.5.2 Shear wave elastography imaging 10.6 Three-dimensional imaging 10.7 High-frequency imaging 10.8 Photoacoustics 10.9 High-intensity focused ultrasound 10.10 Neuromodulation 10.11 Microvascular imaging and super-resolution 10.12 Functional ultrasound 10.13 Material science: nondestructive evaluation/nondestructive testing 10.14 Underwater acoustics and SONAR 10.15 Conclusion References Further reading Appendix A: Ultrasound resources References Appendix B: ASA Physical Acoustics Classification Scheme and terminology Appendix C: IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society terminology Appendix D: Tables of material properties Sources Index Back Cover