The document discusses the basic physics of ultrasound imaging. It covers topics such as:
- Sound waves and their propagation through different media like air, water and tissue. The speed of sound depends on the density and elasticity of the medium.
- The basic principles of image formation using pulse-echo technique. Ultrasound pulses are transmitted into the body and echoes from interfaces between tissues are received to form images.
- Factors that affect image quality like resolution, depth of penetration and frame rate. Interactions of ultrasound with matter including reflection, scattering, refraction and attenuation are also covered.
This document provides an overview of the physics of diagnostic ultrasound. It begins by introducing sound waves and their characteristics such as wavelength, frequency, and speed. It then defines ultrasound and describes the basic principles of image formation including pulse-echo, B-mode, and M-mode imaging. It discusses the four main types of ultrasound interactions with matter: reflection, refraction, scattering, and attenuation. It also describes the construction and operation of ultrasound transducers and instrumentation.
This document provides an overview of ultrasound imaging systems. It discusses how ultrasound uses high frequency sound waves to visualize internal organs and tissues. Key points include:
- Ultrasound uses sound waves above the range of human hearing (above 20 kHz) for medical imaging. It provides 2D, 3D, and 4D images of anatomy.
- The physics of ultrasound involves the longitudinal transmission of sound waves through tissues at different speeds depending on density and elasticity. Reflections at tissue boundaries create echoes that form images.
- Ultrasound transducers use piezoelectric materials like quartz or PZT to transmit sound and detect reflections. Array transducers with multiple elements beamform the ultrasound for
Ultrasound is produced by piezoelectric crystals in transducers that convert electrical pulses into sound waves and received echoes into electrical signals. Transducers operate in shock, burst, or continuous excitation modes. The piezoelectric crystals resonate at specific frequencies determined by their thickness and composition. Damping materials in transducers shorten pulse duration to improve image resolution by reducing echo overlap. Transducers use the pulse-echo principle to transmit sound pulses into the body and receive returning echoes to create ultrasound images.
Welcome to the presentation on the Physical Principles of Ultrasound. Today, we will discuss the fundamental principles underlying medical ultrasound imaging, a crucial tool in radiology. Sound waves with frequencies higher than the upper audible limit of human hearing are called ultrasound.
This document provides an overview of therapeutic ultrasound. It defines ultrasound as a mechanical wave with frequencies too high for human hearing. Ultrasound is generated using piezoelectric crystals that convert electrical oscillations to mechanical vibrations. As ultrasound propagates through tissues, it undergoes attenuation and is absorbed differently based on tissue properties. Pulsed ultrasound is commonly used to allow time for heat dissipation between pulses. Key physical phenomena like reflection, refraction, and absorption influence how ultrasound is transmitted and interacts with tissues.
Ultrasound Basics, Troubleshooting And Outline Of Uses In Anaesthesia is a presentation that covers:
1) The history, physics, and interactions of ultrasound waves including how ultrasound machines work and form images.
2) Current and potential applications of ultrasound in anesthesiology such as regional anesthesia, vascular access, airway assessment, and focused cardiac ultrasound.
3) An overview of ultrasound uses including lung, gastric, and cardiac ultrasound as well as emerging technologies.
Ultrasound uses high frequency sound waves to form images of structures inside the body. It has two main modalities - continuous energy which uses steady sound to detect fetal heartbeats, and pulsed energy which uses quick sound pulses and measures the echo return time to calculate distances. Ultrasound works by using a transducer to transmit sound waves into the body, receiving echoes, and forming images based on echo return times. It is safe, noninvasive, and can detect differences in tissue densities to distinguish structures. The images and Doppler data it provides are useful for medical diagnosis and monitoring.
This document provides an overview of ultrasound physics concepts including:
- How ultrasound waves interact with tissue through attenuation, reflection, scattering, refraction, and diffraction.
- Key properties of ultrasound waves like wavelength, frequency, amplitude, and acoustic impedance.
- Factors that determine image resolution such as transducer frequency and beam focusing.
- Common artefacts that can occur like reverberation, side lobes, and multi-path artefacts.
- The importance of understanding ultrasound physics principles to optimize image quality and avoid misdiagnosis.
This document provides an overview of the physics of diagnostic ultrasound. It begins by introducing sound waves and their characteristics such as wavelength, frequency, and speed. It then defines ultrasound and describes the basic principles of image formation including pulse-echo, B-mode, and M-mode imaging. It discusses the four main types of ultrasound interactions with matter: reflection, refraction, scattering, and attenuation. It also describes the construction and operation of ultrasound transducers and instrumentation.
This document provides an overview of ultrasound imaging systems. It discusses how ultrasound uses high frequency sound waves to visualize internal organs and tissues. Key points include:
- Ultrasound uses sound waves above the range of human hearing (above 20 kHz) for medical imaging. It provides 2D, 3D, and 4D images of anatomy.
- The physics of ultrasound involves the longitudinal transmission of sound waves through tissues at different speeds depending on density and elasticity. Reflections at tissue boundaries create echoes that form images.
- Ultrasound transducers use piezoelectric materials like quartz or PZT to transmit sound and detect reflections. Array transducers with multiple elements beamform the ultrasound for
Ultrasound is produced by piezoelectric crystals in transducers that convert electrical pulses into sound waves and received echoes into electrical signals. Transducers operate in shock, burst, or continuous excitation modes. The piezoelectric crystals resonate at specific frequencies determined by their thickness and composition. Damping materials in transducers shorten pulse duration to improve image resolution by reducing echo overlap. Transducers use the pulse-echo principle to transmit sound pulses into the body and receive returning echoes to create ultrasound images.
Welcome to the presentation on the Physical Principles of Ultrasound. Today, we will discuss the fundamental principles underlying medical ultrasound imaging, a crucial tool in radiology. Sound waves with frequencies higher than the upper audible limit of human hearing are called ultrasound.
This document provides an overview of therapeutic ultrasound. It defines ultrasound as a mechanical wave with frequencies too high for human hearing. Ultrasound is generated using piezoelectric crystals that convert electrical oscillations to mechanical vibrations. As ultrasound propagates through tissues, it undergoes attenuation and is absorbed differently based on tissue properties. Pulsed ultrasound is commonly used to allow time for heat dissipation between pulses. Key physical phenomena like reflection, refraction, and absorption influence how ultrasound is transmitted and interacts with tissues.
Ultrasound Basics, Troubleshooting And Outline Of Uses In Anaesthesia is a presentation that covers:
1) The history, physics, and interactions of ultrasound waves including how ultrasound machines work and form images.
2) Current and potential applications of ultrasound in anesthesiology such as regional anesthesia, vascular access, airway assessment, and focused cardiac ultrasound.
3) An overview of ultrasound uses including lung, gastric, and cardiac ultrasound as well as emerging technologies.
Ultrasound uses high frequency sound waves to form images of structures inside the body. It has two main modalities - continuous energy which uses steady sound to detect fetal heartbeats, and pulsed energy which uses quick sound pulses and measures the echo return time to calculate distances. Ultrasound works by using a transducer to transmit sound waves into the body, receiving echoes, and forming images based on echo return times. It is safe, noninvasive, and can detect differences in tissue densities to distinguish structures. The images and Doppler data it provides are useful for medical diagnosis and monitoring.
This document provides an overview of ultrasound physics concepts including:
- How ultrasound waves interact with tissue through attenuation, reflection, scattering, refraction, and diffraction.
- Key properties of ultrasound waves like wavelength, frequency, amplitude, and acoustic impedance.
- Factors that determine image resolution such as transducer frequency and beam focusing.
- Common artefacts that can occur like reverberation, side lobes, and multi-path artefacts.
- The importance of understanding ultrasound physics principles to optimize image quality and avoid misdiagnosis.
Ultrasound uses high-frequency sound waves to create images of the inside of the body. It works by transmitting sound pulses into the body using a probe. When the pulses hit boundaries between tissues, some of the sound waves are reflected back to the probe. The machine calculates the distance to tissues and organs based on the speed of sound and time of the echo returns, forming a 2D image. Common medical uses of ultrasound include imaging organs in the abdomen and monitoring fetuses during pregnancy.
Ultrasound question and answer document containing 22 questions answered by 7 students. The questions cover topics such as B-mode, Doppler ultrasound, transducer types, image artifacts, and clinical applications. Key points include:
- B-mode creates 2D images from ultrasound echoes of varying brightness. Sector scanning refers to the sweeping motion of the transducer.
- Doppler ultrasound detects blood flow velocity and direction. Types include continuous wave, pulsed wave, duplex, color, and power Doppler.
- Transducer types include linear, curvilinear, and phased array. Probe frequency ranges from 2-15 MHz for different depths and tissues.
Here are quick answers to the review questions:
1. Ultrasound is high frequency sound waves that travel well through soft tissues like muscles, organs and fat. It travels poorly through gas pockets or bones.
2. Higher frequency ultrasound has better resolution but poorer penetration. Lower frequency has poorer resolution but better penetration.
3. Pros of ultrasound include lack of radiation, quick exams, ability to see different tissue planes, portability and lower cost compared to other imaging modalities.
4. Probes come in linear, convex, sector and endocavity shapes. Linear probes have a rectangular footprint for long superficial structures. Convex probes have a curved footprint for abdominal exams. Sector probes have a wedge shape for
This document provides an overview of ultrasonography principles:
- Ultrasonography uses high-frequency sound waves to generate images and is a useful, noninvasive diagnostic tool.
- Sound waves have properties like frequency, wavelength, and velocity that affect image quality. Higher frequencies produce better surface details but poorer penetration.
- Images are produced when sound waves emitted from a transducer's piezoelectric crystals enter the body, encounter tissues, and return echoes that are converted into a visual display.
- Different transducer types and ultrasound modes like B-mode produce various image types used for diagnostic purposes. Artifacts like shadows and reverberations can occur and should be recognized to avoid diagnostic errors.
Ultrasound uses sound waves to produce images of internal organs and tissues. Sound waves are transmitted into the body and the echoes produced by reflections from structures and tissues are detected. Three key points:
1) Ultrasound transducers convert electrical pulses into sound waves which penetrate the body and receive the echoes. Piezoelectric crystals in the transducer perform this function.
2) Reflected sound waves are displayed as images on screen to visualize internal structures. The brightness of each pixel depends on the strength of reflection.
3) Different transducer designs like linear arrays and curved arrays allow imaging of different body regions. Imaging modes like B-mode show anatomical structures while M-mode depicts motion.
This document discusses ultrasound and its properties. It defines ultrasound as mechanical longitudinal waves with frequencies above human hearing (20 kHz). Key properties discussed include:
- Velocity depends on the density and stiffness of the medium and is fastest in solids.
- Frequency ranges from 2-20 MHz, with lower frequencies penetrating deeper but having lower resolution.
- Wavelength is the distance over one cycle and depends on velocity and frequency.
- Amplitude represents intensity and decreases with depth, affecting image brightness.
This document provides an overview of ultrasound physics basics. It discusses how ultrasound uses sound waves between 10-20 MHz to generate images. Sound waves are longitudinal waves that travel through materials at different speeds depending on compressibility and density. Ultrasound imaging works by transmitting pulses into the body and receiving echoes, with transducers converting between electrical and sound signals. Factors like frequency, beam characteristics, and tissue interactions impact the resulting images and potential artifacts. Understanding ultrasound physics principles is important for optimizing scans and interpreting images.
This document provides an overview of ultrasound physics basics. It discusses how ultrasound uses sound waves between 10-20 MHz to generate images. Sound waves are longitudinal waves that travel through materials at different speeds depending on compressibility and density. Ultrasound imaging works by transmitting pulses into the body and receiving echoes, with transducers converting between electrical and sound signals. Factors like frequency, beam characteristics, and tissue interactions impact the resulting images and potential artifacts. Understanding ultrasound physics principles is important for optimizing scans and interpreting images.
Ultrasonography uses high frequency sound waves to produce images of internal organs and structures. Sound waves are transmitted into the body using a transducer, which converts electrical signals to sound and vice versa. Reflections from tissues are detected and used to construct images showing anatomical structures. Key physics principles include velocity, frequency, wavelength, and reflection based on acoustic impedance differences between tissues. Proper transducer design and focused beams are important for optimizing image quality and resolution.
This document provides an overview of the history and physics of ultrasound machines. It discusses how ultrasound works, including how sound waves are produced and received, how images are formed, and factors that affect image quality. The key components of an ultrasound machine are described, including the transducer probe, central processing unit, display, and storage devices. Different ultrasound imaging modes like A-mode, B-mode, and M-mode are introduced along with common medical applications of ultrasound imaging.
This document provides an overview of ultrasound physics principles:
1. It describes how ultrasound works by using a transducer to emit pulses that reflect off tissues and are received back to form an image, and how tissue properties like density and velocity affect reflection and transmission.
2. It explains key ultrasound concepts such as wavelength, frequency, amplitude, acoustic impedance, and gain which determine image quality, as well as Doppler effects which provide blood flow information.
3. The primary components of an ultrasound system are described as the transducer, which emits and receives sound, and the imaging instrument which processes the returning echoes to display an image.
This document discusses ultrasound imaging. It begins with an introduction and then covers ultrasound tissue interaction including reflection, refraction, absorption, attenuation and scattering. It describes the key components of an ultrasound machine including the transducer, CPU, display, control panel, power supply and printer. It explains how ultrasound images are formed, including how the transducer converts electrical energy to sound and how the position and brightness of dots on the image represent reflected echoes. It discusses different ultrasound imaging modes and some common medical applications of ultrasound in obstetrics, cardiology, radiology and vascular medicine.
Ultrasound uses high-frequency sound waves to create images of the inside of the body. It works by passing an electric current through a transducer, causing crystals inside to vibrate and produce ultrasound waves. These waves reflect off tissues and organs and return echoes that are converted into images. The frequency of the ultrasound waves determines properties like axial resolution and penetration depth. Ultrasound is widely used for medical imaging due to being noninvasive, painless, and less expensive than other imaging methods.
This document summarizes a presentation given by Kevin Parker on rapid advances in medical ultrasound. It discusses how ultrasound technology is becoming cheaper, faster, and better through advances like Moore's law that have allowed for the miniaturization of ultrasound components. It describes new portable ultrasound systems and the development of nonlinear imaging techniques that have improved image quality. The document also discusses emerging techniques like elasticity imaging that use ultrasound to assess tissue stiffness and detect tumors, as well as potential new applications in drug delivery guided by ultrasound.
Ultrasound uses high-frequency sound waves to create images of the inside of the body. Sound waves above the range of human hearing, between 2-18 MHz, are used. The speed of sound varies in different tissues, and piezoelectric crystals in the transducer generate and detect sound waves to assess depth and direction of structures. Doppler ultrasound can detect the frequency shift of echoes from moving structures like blood cells to assess blood flow. Technological advances include 3D imaging, portable scanners, and digital storage and sharing of ultrasound images.
Ultrasound physics and image optimization1 (1)Prajwith Rai
This document discusses ultrasound physics and image optimization. It begins with an overview of basic principles, instrumentation, and image optimization techniques. It then describes how ultrasound works, including the generation of sound waves, their interaction with tissues through reflection, refraction, interference and absorption. This determines image quality. Instrumentation components like the transducer, transmitter, receiver and display are explained. Factors affecting the ultrasound beam like frequency, aperture, pulse length and coupling medium are also covered.
production of ultrasound and physical characteristics-Lushinga Mourice
This document provides information on ultrasound physics principles including:
- Ultrasound is generated by piezoelectric crystals that oscillate when electric current is applied, transmitting sound waves. Returning echoes generate a current for imaging.
- Key ultrasound wave properties include amplitude, wavelength, frequency and velocity which impact tissue penetration and resolution.
- Tissue interactions include reflection, scattering, refraction and absorption which are used to visualize internal structures. Acoustic impedance differences cause reflections at boundaries.
- Transducers come in various designs like linear and curvilinear arrays to provide different field of views and resolutions based on application. Controls like power, gain and time gain affect the ultrasound image quality.
This document provides an overview of the physics behind conventional and advanced ultrasound imaging. It begins with introductions to sound waves and ultrasound, then discusses key ultrasound properties like frequency, wavelength, velocity and attenuation. It explains how ultrasound interacts with tissues using principles of reflection, refraction and acoustic impedance. The role of transducers in generating and receiving ultrasound is covered. Methods for focusing beams, steering angles and displaying images are described. Tradeoffs between resolution, penetration depth and frame rates in image creation are also summarized. Overall, the document concisely outlines core physics concepts underlying modern ultrasound technology.
Ultrasound uses longitudinal waves to produce diagnostic images. It transmits sound pulses and receives echoes to determine depth and structures within the body. The document discusses key aspects of ultrasound including its history, components like transducers, and interactions with tissue like reflection, refraction and absorption that allow ultrasound imaging. Transducers convert electrical pulses to sound waves and back using piezoelectric crystals. Factors like frequency, focal length and beam properties affect image resolution and depth.
This document discusses Doppler ultrasonography and the spectral waveforms used to analyze blood flow patterns in vessels. It provides details on:
- The Doppler spectrum which represents blood flow velocities over time on a graph with frequency on the vertical axis and time on the horizontal axis.
- Characteristics of normal flow patterns seen in major vessels and how they relate to vessel anatomy and organ function.
- Abnormal flow patterns seen in pathologies like pseudoaneurysms and arteriovenous fistulas. Pseudoaneurysms show a to-and-fro waveform and arteriovenous fistulas demonstrate elevated continuous flow from the artery into the vein.
The document provides an overview of basic echocardiography. It discusses the history and development of echocardiography. It describes how ultrasound images are generated using transducers that transmit sound waves and receive echoes. Standard echocardiogram views and modalities including 2D, M-Mode, and Doppler are summarized. Indications for echocardiography including assessing valve disease, function, masses and endocarditis are covered in brief.
Ultrasound uses high-frequency sound waves to create images of the inside of the body. It works by transmitting sound pulses into the body using a probe. When the pulses hit boundaries between tissues, some of the sound waves are reflected back to the probe. The machine calculates the distance to tissues and organs based on the speed of sound and time of the echo returns, forming a 2D image. Common medical uses of ultrasound include imaging organs in the abdomen and monitoring fetuses during pregnancy.
Ultrasound question and answer document containing 22 questions answered by 7 students. The questions cover topics such as B-mode, Doppler ultrasound, transducer types, image artifacts, and clinical applications. Key points include:
- B-mode creates 2D images from ultrasound echoes of varying brightness. Sector scanning refers to the sweeping motion of the transducer.
- Doppler ultrasound detects blood flow velocity and direction. Types include continuous wave, pulsed wave, duplex, color, and power Doppler.
- Transducer types include linear, curvilinear, and phased array. Probe frequency ranges from 2-15 MHz for different depths and tissues.
Here are quick answers to the review questions:
1. Ultrasound is high frequency sound waves that travel well through soft tissues like muscles, organs and fat. It travels poorly through gas pockets or bones.
2. Higher frequency ultrasound has better resolution but poorer penetration. Lower frequency has poorer resolution but better penetration.
3. Pros of ultrasound include lack of radiation, quick exams, ability to see different tissue planes, portability and lower cost compared to other imaging modalities.
4. Probes come in linear, convex, sector and endocavity shapes. Linear probes have a rectangular footprint for long superficial structures. Convex probes have a curved footprint for abdominal exams. Sector probes have a wedge shape for
This document provides an overview of ultrasonography principles:
- Ultrasonography uses high-frequency sound waves to generate images and is a useful, noninvasive diagnostic tool.
- Sound waves have properties like frequency, wavelength, and velocity that affect image quality. Higher frequencies produce better surface details but poorer penetration.
- Images are produced when sound waves emitted from a transducer's piezoelectric crystals enter the body, encounter tissues, and return echoes that are converted into a visual display.
- Different transducer types and ultrasound modes like B-mode produce various image types used for diagnostic purposes. Artifacts like shadows and reverberations can occur and should be recognized to avoid diagnostic errors.
Ultrasound uses sound waves to produce images of internal organs and tissues. Sound waves are transmitted into the body and the echoes produced by reflections from structures and tissues are detected. Three key points:
1) Ultrasound transducers convert electrical pulses into sound waves which penetrate the body and receive the echoes. Piezoelectric crystals in the transducer perform this function.
2) Reflected sound waves are displayed as images on screen to visualize internal structures. The brightness of each pixel depends on the strength of reflection.
3) Different transducer designs like linear arrays and curved arrays allow imaging of different body regions. Imaging modes like B-mode show anatomical structures while M-mode depicts motion.
This document discusses ultrasound and its properties. It defines ultrasound as mechanical longitudinal waves with frequencies above human hearing (20 kHz). Key properties discussed include:
- Velocity depends on the density and stiffness of the medium and is fastest in solids.
- Frequency ranges from 2-20 MHz, with lower frequencies penetrating deeper but having lower resolution.
- Wavelength is the distance over one cycle and depends on velocity and frequency.
- Amplitude represents intensity and decreases with depth, affecting image brightness.
This document provides an overview of ultrasound physics basics. It discusses how ultrasound uses sound waves between 10-20 MHz to generate images. Sound waves are longitudinal waves that travel through materials at different speeds depending on compressibility and density. Ultrasound imaging works by transmitting pulses into the body and receiving echoes, with transducers converting between electrical and sound signals. Factors like frequency, beam characteristics, and tissue interactions impact the resulting images and potential artifacts. Understanding ultrasound physics principles is important for optimizing scans and interpreting images.
This document provides an overview of ultrasound physics basics. It discusses how ultrasound uses sound waves between 10-20 MHz to generate images. Sound waves are longitudinal waves that travel through materials at different speeds depending on compressibility and density. Ultrasound imaging works by transmitting pulses into the body and receiving echoes, with transducers converting between electrical and sound signals. Factors like frequency, beam characteristics, and tissue interactions impact the resulting images and potential artifacts. Understanding ultrasound physics principles is important for optimizing scans and interpreting images.
Ultrasonography uses high frequency sound waves to produce images of internal organs and structures. Sound waves are transmitted into the body using a transducer, which converts electrical signals to sound and vice versa. Reflections from tissues are detected and used to construct images showing anatomical structures. Key physics principles include velocity, frequency, wavelength, and reflection based on acoustic impedance differences between tissues. Proper transducer design and focused beams are important for optimizing image quality and resolution.
This document provides an overview of the history and physics of ultrasound machines. It discusses how ultrasound works, including how sound waves are produced and received, how images are formed, and factors that affect image quality. The key components of an ultrasound machine are described, including the transducer probe, central processing unit, display, and storage devices. Different ultrasound imaging modes like A-mode, B-mode, and M-mode are introduced along with common medical applications of ultrasound imaging.
This document provides an overview of ultrasound physics principles:
1. It describes how ultrasound works by using a transducer to emit pulses that reflect off tissues and are received back to form an image, and how tissue properties like density and velocity affect reflection and transmission.
2. It explains key ultrasound concepts such as wavelength, frequency, amplitude, acoustic impedance, and gain which determine image quality, as well as Doppler effects which provide blood flow information.
3. The primary components of an ultrasound system are described as the transducer, which emits and receives sound, and the imaging instrument which processes the returning echoes to display an image.
This document discusses ultrasound imaging. It begins with an introduction and then covers ultrasound tissue interaction including reflection, refraction, absorption, attenuation and scattering. It describes the key components of an ultrasound machine including the transducer, CPU, display, control panel, power supply and printer. It explains how ultrasound images are formed, including how the transducer converts electrical energy to sound and how the position and brightness of dots on the image represent reflected echoes. It discusses different ultrasound imaging modes and some common medical applications of ultrasound in obstetrics, cardiology, radiology and vascular medicine.
Ultrasound uses high-frequency sound waves to create images of the inside of the body. It works by passing an electric current through a transducer, causing crystals inside to vibrate and produce ultrasound waves. These waves reflect off tissues and organs and return echoes that are converted into images. The frequency of the ultrasound waves determines properties like axial resolution and penetration depth. Ultrasound is widely used for medical imaging due to being noninvasive, painless, and less expensive than other imaging methods.
This document summarizes a presentation given by Kevin Parker on rapid advances in medical ultrasound. It discusses how ultrasound technology is becoming cheaper, faster, and better through advances like Moore's law that have allowed for the miniaturization of ultrasound components. It describes new portable ultrasound systems and the development of nonlinear imaging techniques that have improved image quality. The document also discusses emerging techniques like elasticity imaging that use ultrasound to assess tissue stiffness and detect tumors, as well as potential new applications in drug delivery guided by ultrasound.
Ultrasound uses high-frequency sound waves to create images of the inside of the body. Sound waves above the range of human hearing, between 2-18 MHz, are used. The speed of sound varies in different tissues, and piezoelectric crystals in the transducer generate and detect sound waves to assess depth and direction of structures. Doppler ultrasound can detect the frequency shift of echoes from moving structures like blood cells to assess blood flow. Technological advances include 3D imaging, portable scanners, and digital storage and sharing of ultrasound images.
Ultrasound physics and image optimization1 (1)Prajwith Rai
This document discusses ultrasound physics and image optimization. It begins with an overview of basic principles, instrumentation, and image optimization techniques. It then describes how ultrasound works, including the generation of sound waves, their interaction with tissues through reflection, refraction, interference and absorption. This determines image quality. Instrumentation components like the transducer, transmitter, receiver and display are explained. Factors affecting the ultrasound beam like frequency, aperture, pulse length and coupling medium are also covered.
production of ultrasound and physical characteristics-Lushinga Mourice
This document provides information on ultrasound physics principles including:
- Ultrasound is generated by piezoelectric crystals that oscillate when electric current is applied, transmitting sound waves. Returning echoes generate a current for imaging.
- Key ultrasound wave properties include amplitude, wavelength, frequency and velocity which impact tissue penetration and resolution.
- Tissue interactions include reflection, scattering, refraction and absorption which are used to visualize internal structures. Acoustic impedance differences cause reflections at boundaries.
- Transducers come in various designs like linear and curvilinear arrays to provide different field of views and resolutions based on application. Controls like power, gain and time gain affect the ultrasound image quality.
This document provides an overview of the physics behind conventional and advanced ultrasound imaging. It begins with introductions to sound waves and ultrasound, then discusses key ultrasound properties like frequency, wavelength, velocity and attenuation. It explains how ultrasound interacts with tissues using principles of reflection, refraction and acoustic impedance. The role of transducers in generating and receiving ultrasound is covered. Methods for focusing beams, steering angles and displaying images are described. Tradeoffs between resolution, penetration depth and frame rates in image creation are also summarized. Overall, the document concisely outlines core physics concepts underlying modern ultrasound technology.
Ultrasound uses longitudinal waves to produce diagnostic images. It transmits sound pulses and receives echoes to determine depth and structures within the body. The document discusses key aspects of ultrasound including its history, components like transducers, and interactions with tissue like reflection, refraction and absorption that allow ultrasound imaging. Transducers convert electrical pulses to sound waves and back using piezoelectric crystals. Factors like frequency, focal length and beam properties affect image resolution and depth.
This document discusses Doppler ultrasonography and the spectral waveforms used to analyze blood flow patterns in vessels. It provides details on:
- The Doppler spectrum which represents blood flow velocities over time on a graph with frequency on the vertical axis and time on the horizontal axis.
- Characteristics of normal flow patterns seen in major vessels and how they relate to vessel anatomy and organ function.
- Abnormal flow patterns seen in pathologies like pseudoaneurysms and arteriovenous fistulas. Pseudoaneurysms show a to-and-fro waveform and arteriovenous fistulas demonstrate elevated continuous flow from the artery into the vein.
The document provides an overview of basic echocardiography. It discusses the history and development of echocardiography. It describes how ultrasound images are generated using transducers that transmit sound waves and receive echoes. Standard echocardiogram views and modalities including 2D, M-Mode, and Doppler are summarized. Indications for echocardiography including assessing valve disease, function, masses and endocarditis are covered in brief.
Doppler ultrasound utilizes the Doppler effect to detect moving objects like blood cells. It works by transmitting ultrasound pulses and detecting shifts in the frequency of echoes from moving reflectors. There are different Doppler modes including continuous wave, pulsed wave, color Doppler, and spectral Doppler. Optimization involves adjusting settings like gain, filter, sample volume size, and velocity scale. Common artifacts include aliasing, blooming, flash, and mirror artifacts. Doppler ultrasound provides both qualitative and quantitative assessment of blood flow.
This document provides an overview of ultrasound basics, including its history, principles of operation, interactions with tissue, machine components, imaging modes, artifacts, Doppler, elastography, and safety. Key points covered include how ultrasound works via the piezoelectric effect, factors that affect resolution, common artifacts and their clinical value, applications of Doppler and elastography, and that diagnostic ultrasound has been deemed safe by medical organizations.
This document provides an overview of ultrasound physics, transducers, and transducer jelly. It discusses the characteristics of sound waves including their need for a medium, generation through vibration, and properties like frequency and wavelength. It describes the history and components of ultrasound transducers, focusing on how piezoelectric crystals convert electrical signals to sound and vice versa. It also summarizes the key properties and roles of transducer jelly in ultrasound imaging.
This technical document provides an overview of construction practices including foundation work, pillar construction, brickwork, slabs, and other topics. It outlines the steps for foundation work and discusses column details, types of bricks used in construction, issues like dampness, shuttering, cantilever slabs, concrete mixing and testing, roof tiling, plastering, and porch areas. The document aims to provide training on various construction techniques and materials.
Cell Therapy Expansion and Challenges in Autoimmune DiseaseHealth Advances
There is increasing confidence that cell therapies will soon play a role in the treatment of autoimmune disorders, but the extent of this impact remains to be seen. Early readouts on autologous CAR-Ts in lupus are encouraging, but manufacturing and cost limitations are likely to restrict access to highly refractory patients. Allogeneic CAR-Ts have the potential to broaden access to earlier lines of treatment due to their inherent cost benefits, however they will need to demonstrate comparable or improved efficacy to established modalities.
In addition to infrastructure and capacity constraints, CAR-Ts face a very different risk-benefit dynamic in autoimmune compared to oncology, highlighting the need for tolerable therapies with low adverse event risk. CAR-NK and Treg-based therapies are also being developed in certain autoimmune disorders and may demonstrate favorable safety profiles. Several novel non-cell therapies such as bispecific antibodies, nanobodies, and RNAi drugs, may also offer future alternative competitive solutions with variable value propositions.
Widespread adoption of cell therapies will not only require strong efficacy and safety data, but also adapted pricing and access strategies. At oncology-based price points, CAR-Ts are unlikely to achieve broad market access in autoimmune disorders, with eligible patient populations that are potentially orders of magnitude greater than the number of currently addressable cancer patients. Developers have made strides towards reducing cell therapy COGS while improving manufacturing efficiency, but payors will inevitably restrict access until more sustainable pricing is achieved.
Despite these headwinds, industry leaders and investors remain confident that cell therapies are poised to address significant unmet need in patients suffering from autoimmune disorders. However, the extent of this impact on the treatment landscape remains to be seen, as the industry rapidly approaches an inflection point.
Osteoporosis - Definition , Evaluation and Management .pdfJim Jacob Roy
Osteoporosis is an increasing cause of morbidity among the elderly.
In this document , a brief outline of osteoporosis is given , including the risk factors of osteoporosis fractures , the indications for testing bone mineral density and the management of osteoporosis
Promoting Wellbeing - Applied Social Psychology - Psychology SuperNotesPsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Histololgy of Female Reproductive System.pptxAyeshaZaid1
Dive into an in-depth exploration of the histological structure of female reproductive system with this comprehensive lecture. Presented by Dr. Ayesha Irfan, Assistant Professor of Anatomy, this presentation covers the Gross anatomy and functional histology of the female reproductive organs. Ideal for students, educators, and anyone interested in medical science, this lecture provides clear explanations, detailed diagrams, and valuable insights into female reproductive system. Enhance your knowledge and understanding of this essential aspect of human biology.
Rasamanikya is a excellent preparation in the field of Rasashastra, it is used in various Kushtha Roga, Shwasa, Vicharchika, Bhagandara, Vatarakta, and Phiranga Roga. In this article Preparation& Comparative analytical profile for both Formulationon i.e Rasamanikya prepared by Kushmanda swarasa & Churnodhaka Shodita Haratala. The study aims to provide insights into the comparative efficacy and analytical aspects of these formulations for enhanced therapeutic outcomes.
Integrating Ayurveda into Parkinson’s Management: A Holistic ApproachAyurveda ForAll
Explore the benefits of combining Ayurveda with conventional Parkinson's treatments. Learn how a holistic approach can manage symptoms, enhance well-being, and balance body energies. Discover the steps to safely integrate Ayurvedic practices into your Parkinson’s care plan, including expert guidance on diet, herbal remedies, and lifestyle modifications.
- Video recording of this lecture in English language: https://youtu.be/kqbnxVAZs-0
- Video recording of this lecture in Arabic language: https://youtu.be/SINlygW1Mpc
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Does Over-Masturbation Contribute to Chronic Prostatitis.pptxwalterHu5
In some case, your chronic prostatitis may be related to over-masturbation. Generally, natural medicine Diuretic and Anti-inflammatory Pill can help mee get a cure.
TEST BANK For An Introduction to Brain and Behavior, 7th Edition by Bryan Kol...rightmanforbloodline
TEST BANK For An Introduction to Brain and Behavior, 7th Edition by Bryan Kolb, Ian Q. Whishaw, Verified Chapters 1 - 16, Complete Newest Versio
TEST BANK For An Introduction to Brain and Behavior, 7th Edition by Bryan Kolb, Ian Q. Whishaw, Verified Chapters 1 - 16, Complete Newest Version
TEST BANK For An Introduction to Brain and Behavior, 7th Edition by Bryan Kolb, Ian Q. Whishaw, Verified Chapters 1 - 16, Complete Newest Version
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Oleg Kshivets
Overall life span (LS) was 1671.7±1721.6 days and cumulative 5YS reached 62.4%, 10 years – 50.4%, 20 years – 44.6%. 94 LCP lived more than 5 years without cancer (LS=2958.6±1723.6 days), 22 – more than 10 years (LS=5571±1841.8 days). 67 LCP died because of LC (LS=471.9±344 days). AT significantly improved 5YS (68% vs. 53.7%) (P=0.028 by log-rank test). Cox modeling displayed that 5YS of LCP significantly depended on: N0-N12, T3-4, blood cell circuit, cell ratio factors (ratio between cancer cells-CC and blood cells subpopulations), LC cell dynamics, recalcification time, heparin tolerance, prothrombin index, protein, AT, procedure type (P=0.000-0.031). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and N0-12 (rank=1), thrombocytes/CC (rank=2), segmented neutrophils/CC (3), eosinophils/CC (4), erythrocytes/CC (5), healthy cells/CC (6), lymphocytes/CC (7), stick neutrophils/CC (8), leucocytes/CC (9), monocytes/CC (10). Correct prediction of 5YS was 100% by neural networks computing (error=0.000; area under ROC curve=1.0).
1. The Physics of
Diagnostic Ultrasound
FRCR Physics Lectures
Mark Wilson
Clinical Scientist (Radiotherapy)
Hull and East Yorkshire Hospitals
NHS Trust
mark.wilson@hey.nhs.uk
Session 1 & 2
2. Session 1 Overview
Hull and East Yorkshire Hospitals
NHS Trust
Session Aims:
• Basic physics of sound waves
• Basic principles of image formation
• Interactions of ultrasound waves with matter
5. Basic Physics
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Sound Waves
• Sounds waves are mechanical pressure waves which propagate
through a medium causing the particles of the medium to oscillate
backward and forward
•The term Ultrasound refers to sound waves of such a high frequency
that they are inaudible to humans
• Ultrasound is defined as sound waves with a frequency above 20 kHz
• Ultrasound frequencies used for imaging are in the range 2-15 MHz
• The velocity and attenuation of the ultrasound wave is strongly
dependent on the properties of the medium through which it is travelling
6. Basic Physics
Hull and East Yorkshire Hospitals
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Wave Propagation
• Imagine a material as an array of molecules linked by springs
• As an ultrasound pressure wave propagates through the medium, molecules
in regions of high pressure will be pushed together (compression) whereas
molecules in regions of low pressure will be pulled apart (rarefaction)
• As the sound wave propagates through the medium, molecules will oscillate
around their equilibrium position
7. Basic Physics
Hull and East Yorkshire Hospitals
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Power and Intensity
• A sound wave transports Energy through a medium from a source. Energy is
measured in joules (J)
• The Power, P, produce by a source of sound is the rate at which it produces
energy. Power is measured in watts (W) where 1 W = 1 J/s
• The Intensity, I, associated with a sound wave is the power per unit area.
Intensity is measured in W/m2
• The power and intensity associated with a wave increase with the pressure
amplitude, p
Intensity, I p2
Power, P p
8. Basic Physics
Hull and East Yorkshire Hospitals
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Frequency (f):
Number of cycles per second
Unit: Hertz (Hz)
Speed (c):
Speed at which a sound wave
travels is determined by the
medium
Unit: Metres per second (m/s)
Air – 330 m/s
Water – 1480 m/s
Av. Tissue – 1540 m/s
Bone – 3190 m/s
9. Basic Physics
Hull and East Yorkshire Hospitals
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Wavelength ():
Distance between consecutive
crests or other similar points on
the wave
Unit: Metre (m)
A wave from a source of
frequency f, travelling through a
medium whose speed of sound is
c, has a wavelength
= c / f
11. Basic Principles of Image Formation
Hull and East Yorkshire Hospitals
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Pulse-Echo Principle
) ) ) ) )
D
) ) ) )
) ) ) )
)
)
Source of sound
Distance = Speed x Time
2D = c x t
Sound reflected at boundary
Reduced signal amplitude
No signal returns
12. Basic Principles of Image Formation
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Pulse-Echo in Tissue
• Ultrasound pulse is launched into the first tissue
• At tissue interface a portion of ultrasound signal is transmitted into the second
tissue and a portion is reflected within the first tissue (termed an echo)
• Echo signal is detected by the transducer
Transducer
Can transmit
and receive US
Tissue 1 Tissue 2 Tissue 3
13. Basic Principles of Image Formation
B-Mode Image
• A B-mode image is a cross-sectional image representing tissues and organ
boundaries within the body
• Constructed from echoes which are generated by reflection of US waves at
tissue boundaries, and scattering from small irregularities within tissues
• Each echo is displayed at a point in the image which corresponds to the
relative position of its origin within the body
• The brightness of the image at each point is related to the strength
(amplitude) of the echo
• B-mode = Brightness mode
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14. Basic Principles of Image Formation
B-Mode Image Formation
A 2D B-mode image is formed from a large number of B-mode lines, where each
line in the image is produced by a pulse echo sequence
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Transducer
15. Basic Principles of Image Formation
Arrays
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Linear Curvilinear Phased
Rectangular FOV
Useful in applications
where there is a need
to image superficial
areas at the same time
as organs at a deeper
level
Trapezoidal FOV
Wide FOV near
transducer and even
wider FOV at deeper
levels
Sector FOV useful for
imaging heart where
access is normally
through a narrow
acoustic window
between ribs
16. Basic Principles of Image Formation
B-Mode Image – How Long Does it Take?
1. Minimum time for one line = (2 x depth) / speed of sound = 2D / c seconds
2. Each frame of image contains N lines
3. Time for one frame = 2ND / c seconds
E.g. D = 12 cm, c = 1540 m/s, Frame rate = 20 frames per second
Frame rate = c / 2ND
N = c / 2D x Frame rate = 320 lines (poor - approx half of standard TV)
Additional interpolated lines are inserted between image lines to boost image
quality to the human eye
4. Time is very important!!!
Hull and East Yorkshire Hospitals
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17. Basic Principles of Image Formation
Time Gain Compensation (TGC)
• Deeper the source of echo Smaller signal intensity
• Due signal attenuation in tissue and reduction in initial US beam intensity by
reflections
• Operator can TGC use to artificially ‘boost’ the signals from deeper tissues
(like a graphic equaliser)
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18. Basic Principles of Image Formation
M-Mode Image
• Can be used to observe the motion of tissues (e.g. Echocardiography)
• One direction of display is used to represent time rather than space
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Transducer at fixed point Time
Depth
19. Basic Principles of Image Formation
M-Mode Image of Mitral Valve
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22. Ultrasound Interactions
Speed of Sound, c
• The speed of propagation of a sound wave is determined by the medium it is
travelling in
• The material properties which determine speed of sound are density, (mass
per unit volume) and elasticity, k (stiffness)
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Atom / Molecule
Bond
23. Ultrasound Interactions
Speed of Sound, c
• Consider a row of masses (molecules) linked by springs (bonds)
• Sound wave can be propagated along the row of masses by giving the first
mass a momentary ‘push’ to the right
• This movement is coupled to the second mass by the spring
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m m m m
K K K
Sound wave
24. Ultrasound Interactions
• Stiff spring will cause the second mass to accelerate quickly to the right and
pass on the movement to the third mass
• Smaller masses are more easily accelerated by spring
• Hence, low density and high stiffness lead to high speed of sound
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m m m m
K K K
Small masses (m) model a material of low density linked by springs of high
stiffness K
25. Ultrasound Interactions
• Weak spring will cause the second mass to accelerate relatively slowly
• Larger masses are more difficult to accelerate
• Hence, high density and low stiffness lead to low speed of sound
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M M M M
k k k
Large masses (M) model a material of high density linked by springs of low
stiffness k
Speed of Sound c = k /
26. Ultrasound Interactions
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Material C (m/s)
Liver 1578
Kidney 1560
Fat 1430
Average Tissue 1540
Water 1480
Bone 3190
Air 330
27. Ultrasound Interactions - Reflection
Reflection of Ultrasound Waves
When an ultrasound wave travelling through one type of tissue encounters an
interface with a tissue with different acoustic impedance, z, some of its energy
is reflected back towards the source of the wave, while the remainder is
transmitted into the second tissue
- Reflections occur at tissue boundaries where there is a change in acoustic
impedance
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Transducer
z1
z2
28. Ultrasound Interactions - Reflection
Acoustic Impedance (z)
• The acoustic impedance of a medium is a measure of the response of the
particles of the medium to a wave of a given pressure
• The acoustic impedance of a medium is again determined by its density, ,
and elasticity, k (stiffness)
• As with speed of sound, consider a row of masses (molecules) linked by
springs
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m m m m
K K K
Sound wave
29. Ultrasound Interactions - Reflection
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• A given pressure is applied momentarily to the first small mass m
• The mass is easily accelerated to the right and its movement encounters little
opposing force from the weak spring k
• This material has low acoustic impedance, as particle movements are
relatively large in response to a given applied pressure
m m m m
k k k
Small masses (m) model a material of low density linked by weak springs of low
stiffness k
30. Ultrasound Interactions - Reflection
Hull and East Yorkshire Hospitals
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• In this case, the larger masses M accelerate less in response to the applied
pressure
• Their movements are further resisted by the stiff springs
• This material has high acoustic impedance, as particle movements are
relatively small in response to a given applied pressure
M M M M
K K K
Large masses (M) model a material of high density linked by springs of high
stiffness K
Acoustic Impedance z = k
Acoustic Impedance z = c
Can also be shown
31. Ultrasound Interactions - Reflection
Amplitude Reflection Coefficient (r)
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r =
Z2 – Z1
Z1 + Z2
z1 z2
pi , Ii pt , It
pr , Ir
pi
pr
=
32. Ultrasound Interactions - Reflection
Hull and East Yorkshire Hospitals
NHS Trust
Intensity Reflection Coefficient (R)
R =
Z2 – Z1
Z1 + Z2
Ii
Ir
= ( )
2
• Strength of reflection depends on the difference between the Z values of the
two materials
• Ultrasound only possible when wave propagates through materials with
similar acoustic impedances – only a small amount reflected and the rest
transmitted
• Therefore, ultrasound not possible where air or bone interfaces are present
Intensity Transmission Coefficient (T)
T = 1 - R
33. Ultrasound Interactions - Reflection
Hull and East Yorkshire Hospitals
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Interface R T
Soft Tissue-Soft Tissue 0.01-0.02 0.98-0.99
Soft Tissue-Bone 0.40 0.60
Soft Tissue-Air 0.999 0.001
34. Ultrasound Interactions - Reflection
Reflection at an Angle
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z1 z2
i
r
• For a flat, smooth surface the angle of
reflection, r = the angle of incidence, i
• In the body surfaces are not usually
smooth and flat, then r i
35. Ultrasound Interactions - Scatter
Scatter
• Reflection occurs at large interfaces such
as those between organs where there is a
change in acoustic impedance
• Within most organs there are many small
scale variations in acoustic properties
which constitute small scale reflecting
targets
• Reflection from such small targets does
not follow the laws of reflection for large
interfaces and is termed scattering
• Scattering redirects energy in all
directions, but is a weak interaction
compared to reflection at large interfaces
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36. Ultrasound Interactions - Refraction
Refraction
When an ultrasound wave crosses a tissue boundary at an angle (non-normal
incidence), where there is a change in the speed of sound c, the path of the
wave is deflected as it crosses the boundary
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c1 c2 (>c1)
i
t
Snell’s Law
sin (i)
sin (t)
c1
c2
=
37. Ultrasound Interactions - Attenuation
Attenuation
• As an ultrasound wave propagates
through a medium, the intensity
reduces with distance travelled
• Attenuation describes the reduction in
intensity with distance and includes
scattering, diffraction, and absorption
• Attenuation increases linearly with
frequency
• Limits frequency used – trade off
between penetration depth and
resolution
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Distance, d
Intensity, I
Low freq.
High freq.
I = Ioe- d
Where is the attenuation coefficient
38. Ultrasound Interactions - Attenuation
Absorption
• In soft tissue most energy loss (attenuation) is due to absorption
• Absorption is the process by which ultrasound energy is converted to heat in
the medium
• Absorption is responsible for tissue heating
Decibel Notation
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Decibel, dB = 10 log10 (I2 / I1)
Attenuation and absorption is often expressed in terms of decibels
39. Ultrasound Interactions - Diffraction
Diffraction
• Diffraction is the process by which the ultrasound wave diverges (spreads out)
as it moves away from the source
• Divergence is determined by the relationship between the width of the source
(aperture) and the wavelength of the wave
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Low Divergence
Aperture small compared to
High Divergence
Aperture large compared to
41. Session 2 Overview
Hull and East Yorkshire Hospitals
NHS Trust
Session Aims:
• Construction and operation of the ultrasound transducer
• Ultrasound instrumentation
• Ultrasound safety
43. Ultrasound Transducer
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Transducer
• The transducer is the device that converts electrical transmission pulses into
ultrasonic pulses, and ultrasonic echo pulses into electrical signals
• A transducer produces ultrasound pulses and detects echo signals using the
piezoelectric effect
• The piezoelectric effect describes the interconversion of electrical and
mechanical energy in certain materials
• If a voltage pulse is applied to a piezoelectric material, the material will
expand or contract (depending on the polarity of the voltage)
• If a force is applied to a piezoelectric material which causes it to expand or
contract (e.g. pressure wave), a voltage will be induced in the material
45. Ultrasound Transducer
Hull and East Yorkshire Hospitals
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Transducer
• A transducer only generates a useful ultrasound beam at one given frequency
• This frequency corresponds to a wavelength in the transducer equal to twice
the thickness of the piezoelectric disk – This is due to a process known as
Resonance!
• Choice of frequency is important – remember that attenuation increases with
increasing frequency
• Image resolution increases with frequency
• Therefore, there is a trade-off between scan depth and resolution for any
particular application
46. Ultrasound Transducer
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Beam Shape – Diffraction
NEAR FIELD FAR FIELD
NFL
a
Near Field Length, NFL = a2 / a = radius of transducer
= Wavelength
47. Ultrasound Transducer
Hull and East Yorkshire Hospitals
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Beam Shape - Diffraction
• In the near field region the beam energy is largely confined to the dimensions
of the transducer
• Need to select a long near field length to achieve good resolution over the
depth you wish to scan too
• Near field length increases with increasing transducer radius, a, and
decreasing wavelength,
• Short wavelength means high frequency – not very penetrating
• Large transducer radius – Wide beam (poor lateral resolution)
• Trade-off between useful penetration depth and resolution!!
48. Ultrasound Transducer
Hull and East Yorkshire Hospitals
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Beam Focusing
• An improvement to the overall beam width can be obtained by focusing
• Here the source is designed so that the waves converge towards a point in
the beam, the focus, where the beam achieves its minimum width
• Beyond the focus, the beam diverges again but more rapidly that for an
unfocused beam with the same aperture and frequency
49. Ultrasound Transducer
Hull and East Yorkshire Hospitals
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Beam Focusing
a
W
F
Beam width at focus, W = F / a
At focal point:
• Maximum ultrasound intensity
• Maximum resolution
50. Ultrasound Transducer
Hull and East Yorkshire Hospitals
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Beam Focusing
For a single element source, focusing can be achieved in one of two ways:
1) A curved source
A curved source is manufactured with a radius of curvature of F and
hence produces curved wave fronts which converge at a focus F cm from
the source
F
Source Focus
51. Ultrasound Transducer
Hull and East Yorkshire Hospitals
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Beam Focusing
For a single element source, focusing can be achieved in one of two ways:
2) An acoustic lens
An acoustic lens is attached to the face of a flat source and produces
curved wave fronts by refraction at its outer surface (like an optical lens).
A convex lens is made from a material with the lower speed of sound
than tissue.
Source Focus
Lens
52. Ultrasound Transducer
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Beam Shape - Overlapping Groups of Elements
Fire elements
1-5 together
And then…
Fire elements
2-6 together
And so on…
Near field length increases as (N)2
53. Ultrasound Transducer
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Array Focusing
Waves from outer elements 1 and 5 have
greater path lengths than those from other
elements
Therefore signals do not arrive simultaneously
at the target and reflections do not arrive at all
elements at the same time
54. Ultrasound Transducer
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Array Focussing
Introduce time delays to compensate for extra
path length on both transit and receive
Time delays
55. Ultrasound Transducer
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Multiple Zone Focussing
• Fire transducer several times with different focus to compile better image
• However, more focus points decreases frame rate
56. Ultrasound Transducer
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Resolution
Resolution in three planes
Axial Slice Thickness
Lateral
57. Ultrasound Transducer
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Resolution
Resolution Depends on Typical Value (mm)
Axial Pulse length 0.2 - 0.5
Lateral Beam width 2 – 5
Slice Thickness Beam height 3 - 8
• Higher frequency improves resolution in all three planes
• Slice thickness is a hot topic for improvement – 2D arrays
59. Instrumentation
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Transmitter Clock
TGC Generator Transducer Beam Controller
AD Converter
Signal Processor Image Store
Archive Display
x, y
z
60. Instrumentation
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Clock
• Command and control centre
• Sends synchronising pulses around the system
• Each pulse corresponds to a command to send a new pulse from the
transducer
• Determines the pulse repetition frequency (PRF)
PRF = 1 / time per line = c / 2D
Where c is speed of sound and D is maximum scan depth
If there are N lines, then Frame Rate = c / 2ND
61. Instrumentation
Transmitter
• Responds to clock commands by generating high voltage pulses to
excite transducer
Transducer
• Sends out short ultrasound pulses when excited
• Detects returning echoes and presents them as small electrical
signals
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62. Instrumentation
AD Converter
• Converts analogue echo signals into digital signals for further
processing
Needs to:
• Be fast enough to cope with highest frequencies
• Have sufficient levels to create adequate grey scales (e.g. 256 or 512)
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63. Instrumentation
Signal Processor
Carries out:
• TGC application
• Overall gain
• Signal compression – fits very large dynamic range ultrasound signal
on to limited greyscale display dynamic range
• Demodulation – removal of the carrier (ultrasound) frequency
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Grey level
Input Amp
Linear
Liver
Heart
64. Instrumentation
Image Store
• Takes z (brightness) signal from processor
• Positions it in image memory using x (depth) and y (element position)
information from beam controller
• Assembles image for each frame
• Presents assembled image to display
• Typically have capacity to store 100-200 frames to allow cine-loop
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66. Ultrasound Safety
Hazard and Risk
• Hazard describes the nature of the danger or threat (e.g. burning,
falling, etc)
• Risk takes into account the severity of the potential consequences
(e.g. death, injury) and the probability of occurrence
• There are two main hazards associated with ultrasound:
- Tissue heating
- Cavitation
• But is there any risk???
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67. Ultrasound Safety
Tissue Heating
• During a scan some of the ultrasound energy is absorbed by the exposed
tissue and converted to heat causing temperature elevation
• Elevated temperature affects normal cell function
• The risk associated with this hazard depends on the:
- Degree of temperature elevation
- Duration of the elevation
- Nature of the exposed tissue
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Rate of energy absorption per unit volume
q = 2I
Where = absorption coefficient, = frequency, I = intensity
68. Ultrasound Safety
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Tissue Heating
• Thermal effects in patient are complex
• Temperature increase will be fastest at the focus resulting in a temperature
gradient
• Heat will be lost from focus by thermal conduction
• The transducer itself will heat up and this heat will conduct into tissue
enhancing the temperature rise near the transducer
• The presence of bone in the field will increase the temperature rise
• Blood flow will carry heat away from the exposed tissues
• It is impossible to accurately predict the temperature increase occurring in the
body and a simple approach to estimate the temperature increase is used to
provide some guidance - Thermal Index (TI)
69. Ultrasound Safety
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Thermal Index (TI)
TI = W / Wdeg
W = Transducer power exposing the tissue
Wdeg = The power required to cause a maximum temperature rise of 1oC
anywhere in the beam
• TI is a rough estimate of the increase in temperature that occurs in the region
of the ultrasound scan
• A TI of 2.0 means that you can expect at temperature rise of about 2oC
• The difficulty with calculating the TI lies mostly in the estimation of Wdeg
• To simplify this problem there are three TIs
70. Ultrasound Safety
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Soft-Tissue Thermal Index (TIS)
Soft tissue
Maximum temperature
Bone-at-Focus Thermal Index (TIB)
Soft tissue
Maximum temperature
Bone
71. Ultrasound Safety
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Cranial (or Bone-at-Surface) Thermal Index (TIC)
Soft tissue
Maximum temperature
Bone
All three TI values depend linearly on the acoustic power emitted by the
transducer
72. Ultrasound Safety
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Does Temperature Rise Matter?
• Normal core temperature is 36-38oC and a temperature of 42oC is “largely
incompatible with life”
• During an ultrasound examination only a small volume of tissue is exposed and
the human body is quite capable of recovering from such an event
• Some regions are more sensitive such as reproductive cells, unborn fetus, and
the CNS
• Temperature rises of between 3 and 8oC are considered possible under certain
conditions
• There has been no confirmed evidence of damage from diagnostic ultrasound
exposure
73. Ultrasound Safety
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Cavitation
• Refers to the response of gas bubbles in a
liquid under the influence of an ultrasonic wave
• Process of considerable complexity
• High peak pressure changes can cause micro-
bubbles in a liquid or near liquid medium to
expand – resonance effect
• A bubble may undergo very large size variations
and violently collapse
• Very high localised pressures and temperature
are predicted that have potential to cause cellular
damage and free radical generation
74. Ultrasound Safety
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Cavitation
Micro-bubbles grow by resonance processes
Bubbles have a resonant frequency, fr, depending on their radius, R.
frR 3 Hz m
This suggests that typical diagnostic frequencies (3 MHz and above) cause
resonance in bubbles with radii of the order of 1 micrometer
75. Ultrasound Safety
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Mechanical Index (MI)
• The onset of cavitation only occurs above a threshold for acoustic pressure
• This has resulted in the formulation of a mechanical index (MI)
• Mechanical index is intended to quantify the likelihood of onset of cavitation
MI = pr / f
where pr is the peak rarefaction pressure and f is the ultrasound frequency
• For MI 0.7 the physical conditions probably cannot exist to support bubble
growth and collapse
• Exceeding this threshold does not mean there will be automatically be
cavitation
• Cavitation is more likely in the presence of contrast agents and in the
presence of gas bodies such as in the lung and intestine