Ultrasound Technology for Clinical Practitioners

Description

Ultrasound Technology for Clinical Practitioners A hands-on and practical roadmap to ultrasound technology for clinical practitioners who use it every day In Ultrasound Technology for Clinical Practitioners, distinguished medical physicist and vascular ultrasound scientist Crispian Oates delivers an accessible and practical resource written for the everyday clinical user of ultrasound. The book offers complete descriptions of the latest techniques in ultrasound, including ultrafast ultrasound and elastography, providing an up-to-date and relevant resource for educators, students, and practitioners alike. Ultrasound Technology for Clinical Practitioners uses a first-person perspective that walks readers through a relevant and memorable story containing necessary information, simplifying retention and learning. It makes extensive use of bulleted lists, diagrams, and images, and relies on mathematics and equations only where necessary to illustrate the relationship between other factors. Physics examples come from commonly known contexts that readers can relate to their everyday lives, and additional description boxes offer optional, helpful info in some topic areas. Readers will also find: A thorough introduction to the foundational physics of ultrasound, as well as the propagation of the ultrasound pulse through tissue Comprehensive discussions of beam shapes, transducers, imaging techniques, and pulse echo instrumentation In-depth examination of image quality and artefacts and the principles of Doppler and colour Doppler ultrasound Fulsome treatments of measurement taking and safety and quality assurance in ultrasound Perfect for sonographers, echocardiographers, and vascular scientists, Ultrasound Technology for Clinical Practitioners will also earn a place in the libraries of radiologists, cardiologists, emergency medicine specialists, and all other clinical users of ultrasound. Cover Title Page Copyright Page Contents Acknowledgments List of Abbreviations Introduction CHAPTER 1 The Basic Physics of Ultrasound Sound Waves Describing Waves Energy in a Sound Wave Ultrasound Pulses Energy Spectrum of a Pulse Bandwidth Quality Factor Speed of Sound (C) Characteristic Acoustic Impedance, Z0 Energy in a Sound Wave Decibels CHAPTER 2 The Interaction of Ultrasound with Tissue Reflection and Transmission at a Plane Interface Specular Reflection Reflection at an Angle and Refraction Poor Visualisation Scattering Total Scattered Power The Speckle Pattern Attenuation Attenuation Coefficient (á) Summary The Journey of the Ultrasound Pulse User Control Transmit Power References CHAPTER 3 Beam Shapes Simple Beam Shape Model Huygen’s Wavelet Model and Diffraction Focusing Beam Forming with Transducer Arrays Grating Lobes Apodization Beam Steering Beam Shape and Beam Steering Electronic Focusing Resolution Axial Resolution Lateral Resolution Resolution Versus Penetration Clutter Reference CHAPTER 4 The Ultrasound Probe The Transducer Piezoelectric Effect Single Crystal Technology Resonant Frequency Backing Layer Matching Layer Front Face Lens Wide Band Transducers Construction of an Array CMUT Technology 1-D, 1.5-D, and 2-D Arrays The Hanafy Lens 1.5-D Array 2-D Array References CHAPTER 5 Image Formation Image Modes A-Mode (Amplitude Mode) M-Mode (Motion Mode) B-Mode or Greyscale Image (Brightness Mode) Linear Image Formation Linear Array Frame Rate Curvilinear Array Phased Array Extended Field of View Panoramic View 3D Imaging Hand Scanning Mechanical 3D Probe 2D Matrix Array 3D Image Display Cine Loop Endoprobes Choosing A Probe Focusing Transmit Focus Receive Focus Increasing Frame Rate Synthetic Aperture Imaging User Control Resolution/Penetration Ultrasound Harmonics Harmonic Imaging Pros and Cons of Harmonic Imaging Coded Excitation References CHAPTER 6 The B-Mode Scanner Transmission Side of a Scanner Beam Former PRF – Pulse Repetition Frequency User Controls Transmit Power Depth of Focus Receive Side of a Scanner (RX) Beam Former Gain User Controls – Gain Time Gain Compensation Analogue to Digital Converter – ADC Advantages of Digitising Echo Detection Dynamic Range and Transfer Function (Greyscale Mapping) Dynamic Range Transfer Function or Grey Scale Mapping Contrast Resolution User Controls Image Memory Frame Freeze Read and Write Zoom Read Zoom Write Zoom Image Processing User Control Exam Presets Measurements CHAPTER 7 Image Quality and Artefacts Acoustic Window Frame Rate: Frames Per Second (fps) Interlacing Scan Lines Interpolation – Writing in ‘Extra Lines’ Speckle Frame Averaging or Persistence User Control Spatial Compound Imaging Adaptive Filtering Edge Enhancement Contrast Resolution Noise in an Image Colour Enhancement of Greyscale Images Human Visual Perception How to Set Up a Monitor Image Flicker Ambient Lighting Artefacts Assumptions Speed of Sound Artefacts Refraction Axial Misplacement Attenuation Artefacts Poorly Adjusted Time Gain Control (TGC) Acoustic Shadowing Post Cystic Enhancement Shadowing from the Transducer Surface Reflection Artefacts Mirror Image Artefact Reverberation Reverberation Artefact Probe – Interface Reverberation Ringdown Comet Tail or Ringing Anisotropy Beam Shape Artefacts Slice Thickness Artefact Side Lobes and Grating Lobes Temporal Artefacts Image Blurring Final Example References CHAPTER 8 Principles of Doppler Ultrasound The Doppler Effect The Doppler Equation Duplex Ultrasound CW Doppler Block Diagram of CW Doppler Instrument Detection of Direction of Flow The Doppler Waveform Display (Sonogram) Examples 1. Slowly Moving Blood Flow in a Vessel 2. Fast Moving Blood Flow in a Vessel CW Doppler Summary Pulsed Wave Doppler (PW Doppler) and Range Gating Detection of the Doppler Signal Block Diagram of Pulsed Doppler Instrument with Sonogram Display Aliasing Appearance of Aliasing on the Sonogram Observing Low Velocities PW Doppler Summary The PW Doppler Pulses Intrinsic Spectral Broadening (ISB) Question: What Doppler Angle Should We Use? User Controls Angle Correction Doppler Beam Steering Length and Depth of Sample Volume Scale Sweep Speed Baseline Offset and Invert Doppler Transmit Power Doppler Gain Peak Velocity Envelope Autotrace Average Velocity Doppler Artefacts Aliasing Intrinsic Spectral Broadening Wall Thump User Control Waveform Ghosting Shadowing References CHAPTER 9 Principles of Colour Doppler Ultrasound Autocorrelation Colour Scale Frame Rate User Controls Colour Box Frame Averaging Sampling CDU and the Doppler Angle Colour Aliasing User Controls Scale Invert Discrimination of Stationary Targets Imaging Small Vessels User Controls Wall Filter B-Mode Priority Power Doppler (PD) CDU Artefacts Aliasing Shadowing Wall Discrimination Flash Artefact Mirror Image Twinkle Artefact Temporal Artefact Colour Sensitivity Presets Colour M-Mode Tissue Doppler Imaging (TDI) Myocardial Strain Imaging Strain Strain Rate (SR) Using TDI to Measure Strain Speckle Tracking Echocardiography STE STE Display References CHAPTER 10 Making Measurements Accuracy Precision How Accurate or Precise Do We Need To Be? Reproducibility Systematic and Random Errors Random Errors Ultrasound Measurements in Practice Physical Constraints Scaling Caliper Accuracy Image Resolution Sonographer-Based Constraints Principles for Making Reliable Measurements Target Visualisation Frame Freeze Use First Interface Measurements Protocols Actual Measurements Factoring Variability Ultrafine Measurements Measurement of Circumference, Area, and Volume Direct Measurement Assume a Simple Shape Use a Simplified Model of the Target Slicing Models Surface Segmentation and Automated Methods Doppler Waveform Measurements Image/Sonogram Size Scale Gain Freeze the Image Weak Signals Doppler Angle Waveform Indices Pulsatility Index (PI) Resistance Index (RI) A/B Ratio Colour Doppler Ultrasound Measurement of Volume Flow Q Cross-Section Area A Average Velocity References CHAPTER 11 Safety and Quality Assurance Energy, Power, and Intensity Measuring Intensity Intensity Factors Affecting Damage Potential Thermal Effects Thermal Index (TI) TIS TIB TIC Transducer Self-Heating Nonthermal Effects Radiation Force Streaming Cavitation Mechanical Index (MI) ALARA Contrast Agents Clinical Risk Bio-effects from Ultrasound Quality Assurance and Routine Checks Suggested Routine User Checks Annual Service The Use of Test Objects Personal Risk Management WRRSI Risk Mitigation In Summary New Techniques in Ultrasound References CHAPTER 12 Advanced Topics Contrast Agents (CA) Behaviour of Bubbles in the Ultrasound Field Contrast Agent Harmonics Amplitude Modulation Pulse Inversion Flashing Advanced Micro-Bubble Techniques B-Flow Blood Vessel Imaging Doppler Measurement of Pressure Gradients Advanced Image Processing Artificial Intelligence Segmentation Examples (1–3) Computer-Aided Diagnosis (CAD) Feature Identification Examples Classification Deep Learning Diagnosis with Cad Examples of CAD Fusion Imaging Needle Visualisation and Guidance References CHAPTER 13 Ultrafast Ultrasound Synthetic Aperture Imaging (SA) Plane-Wave Beamforming Summary Speed of Sound Correction Benefits Ultrafast Doppler Ultrafast Colour Doppler (UFCD) Microvascular Imaging Pulsed Wave Doppler (PW) Vector Flow Imaging (VFI) The Flow Vector Directional Beam Forming Transverse Oscillation (TO) Display of Flow Vectors Vector Display Colour Display References CHAPTER 14 Elastography Background Theory Elastography Methods of Applying The Distorting Force Strain Elastography (SE) SE with Manual or Physiological Palpation User Controls Frequency Frame Rate Tracking Window Frame Reject Noise Reject Line Density Frame Averaging Dynamic Range Colour Map Colour Blend SE Artefacts Stress Concentration Artefacts Edge Enhancement Effects Appearance of Cysts Blue/Green/Red Artefact Shadowing Acoustic Radiation Force Impulse Imaging (ARFI Imaging) Pros and Cons of ARFI Strain Ratio Shear Wave Elastography (SWE) Background Theory Point SWE (PSWE) Supersonic Shear Imaging (SSI) Shear Wave Compounding SWE Artefacts Bang Artefact References Appendix 1: Knobology Appendix 2: Handling Equations and Decibels Appendix 3: The Unfocused Transducer Beam Shape Index EULA