The document discusses the Stanford UHF MRI program and its engineering challenges at ultra-high magnetic field strengths. It provides an introduction to UHF MRI and outlines key challenges including increased radio frequency (RF) heating, B1 inhomogeneities, B0 inhomogeneities, acoustic noise and vibrations. It summarizes research at Stanford to address B1 inhomogeneities through parallel transmission coil design and dielectric shimming techniques. It also discusses work to address B0 inhomogeneities through active and passive shimming methods including a novel RF shim coil design.
Passive millimeter wave imaging using subharmonic self-oscillating mixingSimone Angela Winkler
The usefulness of passive millimeter-wave imaging lies in particular in the peculiarities of atmospheric attenuation phenomenologies allowing millimetre-waves to penetrate through a variety of low-visibility conditions such as haze, fog, clouds, smoke, and sandstorms and furthermore in the ability to propagate through clothing and a number of other materials. Present and future applications consist in both military and
commercial infrastructure fields such as in surveillance, navigation, and automotive technology, security screening systems, and biomedical imaging. My work in this field focused on the development of novel types of receivers using self-oscillating mixing technology based on nonlinear subharmonic principles.
High speed DDS controlled radar system for the identification of Surface Acou...Simone Angela Winkler
This document describes a high-speed radar system for identifying moving surface acoustic wave tags. It consists of a direct digital synthesizer, analog-to-digital converter, digital signal processor, and RF frontend to generate chirp signals, acquire return signals, and perform frequency analysis to identify tags. Measurements show the system can identify two tags in motion at 6.9 m/s over a period of less than 10 ms. The system is able to perform measurements of tags in motion with the same signal-to-noise ratio as for static tags.
Three sentences:
Sound waves are mechanical waves that propagate through a medium as variations in pressure. Acoustic sensors convert these pressure variations into electrical signals using various transduction mechanisms like piezoelectricity, capacitance changes, or fiber optic interferometry. Common acoustic sensors include microphones, hydrophones, and surface acoustic wave sensors which propagate mechanical waves along the surface of piezoelectric materials to enable highly sensitive measurement.
Surface acoustic wave sensors rely on modulating and transducing surface acoustic waves to sense physical phenomena. They have advantages including compact size, high sensitivity, fast response, and ability to operate wirelessly in harsh environments. A basic SAW sensor consists of a piezoelectric substrate with input and output interdigital transducers to launch and receive surface acoustic waves. The transducers convert between electrical and mechanical surface waves, allowing remote sensing by analyzing signal changes induced by external factors interacting with the waves.
Describes about the principle and working of a general SAW sensor, and also describes about the SAW based wireless microactuator for the biomedical applications
IMAGE RECONSTRUCTION IN MRI(7th chapter)Joshua Mathew
This document discusses slice selection in MRI imaging. It describes how slice selection works by using gradients and RF pulses with a specific frequency bandwidth to excite only protons within a slice of a certain thickness. The slice select gradient is used along with an RF pulse to select the desired slice location. Narrowing the RF pulse bandwidth or increasing the slice select gradient decreases slice thickness. Selective RF pulses are used to excite a single slice, while nonselective pulses excite the entire imaging region.
MRI uses strong magnetic fields and radio waves to produce diagnostic images of the body. There are three main types of MRI magnets - permanent magnets which use iron alloys, resistive magnets which require large power supplies, and superconductive magnets which use niobium alloys cooled with liquid helium. Safety is crucial with MRI due to the strong magnetic fields which can pull metal objects or cause interference. Different pulse sequences such as T1-weighted, T2-weighted, and FLAIR are used to visualize tissues and abnormalities in the brain.
Passive millimeter wave imaging using subharmonic self-oscillating mixingSimone Angela Winkler
The usefulness of passive millimeter-wave imaging lies in particular in the peculiarities of atmospheric attenuation phenomenologies allowing millimetre-waves to penetrate through a variety of low-visibility conditions such as haze, fog, clouds, smoke, and sandstorms and furthermore in the ability to propagate through clothing and a number of other materials. Present and future applications consist in both military and
commercial infrastructure fields such as in surveillance, navigation, and automotive technology, security screening systems, and biomedical imaging. My work in this field focused on the development of novel types of receivers using self-oscillating mixing technology based on nonlinear subharmonic principles.
High speed DDS controlled radar system for the identification of Surface Acou...Simone Angela Winkler
This document describes a high-speed radar system for identifying moving surface acoustic wave tags. It consists of a direct digital synthesizer, analog-to-digital converter, digital signal processor, and RF frontend to generate chirp signals, acquire return signals, and perform frequency analysis to identify tags. Measurements show the system can identify two tags in motion at 6.9 m/s over a period of less than 10 ms. The system is able to perform measurements of tags in motion with the same signal-to-noise ratio as for static tags.
Three sentences:
Sound waves are mechanical waves that propagate through a medium as variations in pressure. Acoustic sensors convert these pressure variations into electrical signals using various transduction mechanisms like piezoelectricity, capacitance changes, or fiber optic interferometry. Common acoustic sensors include microphones, hydrophones, and surface acoustic wave sensors which propagate mechanical waves along the surface of piezoelectric materials to enable highly sensitive measurement.
Surface acoustic wave sensors rely on modulating and transducing surface acoustic waves to sense physical phenomena. They have advantages including compact size, high sensitivity, fast response, and ability to operate wirelessly in harsh environments. A basic SAW sensor consists of a piezoelectric substrate with input and output interdigital transducers to launch and receive surface acoustic waves. The transducers convert between electrical and mechanical surface waves, allowing remote sensing by analyzing signal changes induced by external factors interacting with the waves.
Describes about the principle and working of a general SAW sensor, and also describes about the SAW based wireless microactuator for the biomedical applications
IMAGE RECONSTRUCTION IN MRI(7th chapter)Joshua Mathew
This document discusses slice selection in MRI imaging. It describes how slice selection works by using gradients and RF pulses with a specific frequency bandwidth to excite only protons within a slice of a certain thickness. The slice select gradient is used along with an RF pulse to select the desired slice location. Narrowing the RF pulse bandwidth or increasing the slice select gradient decreases slice thickness. Selective RF pulses are used to excite a single slice, while nonselective pulses excite the entire imaging region.
MRI uses strong magnetic fields and radio waves to produce diagnostic images of the body. There are three main types of MRI magnets - permanent magnets which use iron alloys, resistive magnets which require large power supplies, and superconductive magnets which use niobium alloys cooled with liquid helium. Safety is crucial with MRI due to the strong magnetic fields which can pull metal objects or cause interference. Different pulse sequences such as T1-weighted, T2-weighted, and FLAIR are used to visualize tissues and abnormalities in the brain.
MEMS Approach to Low Power Wearable Gas SensorsMichael Lim
This presentation gives an overview of candidates solid state MEMS structures for wearable monitoring systems. The basic transduction mechanisms and device structures are shown for 5 types: QCM, FBAR, SAW, Cantilever, and CMUT. Finally, the structures are compared for their application into these mobile systems.
PARTICLE SEPARATION, CHEMICAL GRADIENT CONTROL AND MICROMIXING VIA FOCUSED TR...Ghulam Destgeer
1) The document discusses using focused travelling surface acoustic waves (F-TSAW) to separate particles, generate chemical gradients, and mix fluids in a microfluidic channel.
2) F-TSAW can continuously separate particles by size due to differences in acoustic radiation force and acoustic streaming flow effects. Chemical gradients are also generated through symmetrical owl's eye vortices created by acoustic streaming flow.
3) The presented F-TSAW microchip combines label-free particle separation, adjustable and rapidly switching chemical gradient generation, and uniform micromixing in a single portable device.
Surface Acoustic Wave Technology
Surface acoustic waves (SAW) propagate along the surface of piezoelectric materials and can be used to process signals. A SAW device consists of interdigital transducers (IDTs) and reflectors on a piezoelectric substrate that convert electrical signals to surface acoustic waves and vice versa. SAW devices are used in a wide range of applications including filters, sensors, and touchscreens. Touchscreens use SAW devices to detect touch locations by measuring wave absorption. SAW technology provides advantages such as low cost and power consumption but also has disadvantages like temperature dependence.
Surface acoustic wave (saw) radio transpondersRehan Fazal
A surface acoustic wave (SAW) radio transponder uses surface acoustic waves to enable remote sensing capabilities. SAW transponders consist of interdigital transducers that convert electromagnetic signals into acoustic waves that propagate along the surface of a piezoelectric material. These waves are then reconverted into electromagnetic signals by the transducers. SAW transponders are passive, wireless, and maintenance-free, making them well-suited for applications like temperature sensing on power lines. One key application is in tire pressure monitoring systems (TPMS), where the SAW device acts as a pressure sensor diaphragm to remotely measure tire pressure.
The document describes a new microwave life detection system that can locate human victims trapped under earthquake rubble. The system works by sending microwave beams through rubble at L-band frequency, which can penetrate deeper than other frequencies. Any signals reflected from a trapped victim's breathing and heartbeat movements would be detected. A clutter cancellation system filters out fixed reflections from rubble while preserving modulated signals from living beings. The system could help reduce loss of life from earthquakes by remotely detecting trapped humans within seconds.
Why Use SAW Sensors and Tags?
- Frequency/time are measured with greatest accuracy compared to any other physical measurement (10-10 - 10-14).
- External stimuli affects device parameters (frequency, phase, amplitude, delay)
- Operate from cryogenic to >1000oC
- Ability to both measure a stimuli and to wirelessly, passively transmit information
- Frequency range ~10 MHz – 3 GHz
- Monolithic structure fabricated with current IC photolithography techniques, small, rugged
Radiographic testing uses penetrating radiation directed at a component. Differences in how radiation is absorbed can be recorded on film or digitally to detect internal defects. There are various radiation sources and imaging methods used, including film, computed radiography, real-time radiography, and digital radiography. Strict safety protocols must be followed when using radiation to inspect components and ensure technician and public safety.
This document discusses and compares surface acoustic wave (SAW) devices and bulk acoustic wave (BAW) devices. SAW devices propagate waves along a material surface and are used in delay lines, filters, and other electronic components below 1 GHz. BAW devices propagate waves through the bulk material and can operate above 2 GHz in smaller sizes with less temperature sensitivity than SAW devices. Both SAW and BAW devices find applications in communications, radar, and other systems due to their filtering and signal processing capabilities.
The document provides an overview of the fundamentals of CT and MRI imaging. It discusses how CT was introduced in 1972 and revolutionized medical imaging by providing high-quality transverse cross-sectional images of the body without tissue superimposition. It also describes the evolution of CT technology from early generation pencil-beam systems to current helical CT scanners that acquire continuous data as the patient passes through the rotating gantry. Key developments included increasing the number of detectors to acquire wider beams, implementing rotating gantries to speed up scans, and incorporating slip-ring technology to allow continuous 360-degree rotation.
MRI uses magnetic fields and radio waves to produce detailed images of the brain and detect abnormalities. It is based on nuclear magnetic resonance, where hydrogen protons in the body are aligned by a strong magnetic field. When hit with radio waves of a specific frequency, the protons absorb energy and spin, and emit radio signals as they relax back to baseline. These signals are used to construct images, with different tissues appearing different intensities based on their relaxation times T1 and T2. MRI provides valuable information to assess many neurological conditions without using ionizing radiation.
Life Detection Using Microwaves TechnologySai Spandana
One of my first attempts to make a presentation. This presentation is based on a Research Article titled "A MODERN MICROWAVE LIFE DETECTION SYSTEM FOR
HUMAN BEING BURIED UNDER RUBBLE" published in the International Journal of Advanced Engineering Research and Studies
MRI image quality is affected by several factors including signal-to-noise ratio, receive bandwidth, noise sources, and spatial resolution. A higher signal-to-noise ratio provides better image quality. Receive bandwidth determines the range of frequencies received and affects chemical shift artifact and readout time. Noise in MRI comes from electronic noise and fluctuations in body tissues. Spatial resolution is influenced by receive bandwidth, matrix size, slice thickness, and field of view. Contrast resolution depends on tissue T1 and T2 values and the timing of pulse sequences. Motion contrast methods like diffusion weighting and flow weighting provide additional tissue information.
This is how we can save many life during any natural calamity like earthquake etc.., or if any building collapse then we can use this system which can detect the heart beats of those who are under the collapsed building.
The document discusses the parts and functioning of an x-ray machine. It is comprised of an x-ray tube, transformer, tube stand, and control panel. The x-ray tube produces electromagnetic radiation when electric current is supplied by the transformer. The images are recorded digitally on a computer after the radiation passes through the body. The document also provides a brief history of x-rays from their discovery in 1895 to the introduction of digital x-ray technology in 1997.
Radiography uses x-rays or gamma rays to detect flaws in materials. X-rays are produced when high-speed electrons collide with a metal target, while gamma rays come from radioactive isotopes. As the radiation passes through an object, areas of different thickness or density absorb differing amounts, forming an image on film or digitally. Radiography is widely used in industries like aerospace, military, and manufacturing to inspect components for defects without destroying them. Proper safety procedures must be followed due to the ionizing nature of x-rays and gamma rays.
X ray machines - conventional and digitalUrfeya Mirza
X-ray machines use high-energy electromagnetic radiation to generate digital or film images of the internal structures of objects. Conventional x-ray machines use film that must be developed, while digital x-ray machines directly convert x-rays to electrical signals and display images digitally. Both use an x-ray tube to generate x-rays, which are controlled via technique factors selected on the machine's control panel. Digital x-ray offers advantages like adjustable images and compatibility with digital record systems.
The document provides an overview of the history and development of magnetic resonance imaging (MRI) technology. It discusses several key figures who contributed discoveries that advanced MRI, such as Felix Bloch and Edward Purcell conducting the first NMR experiment in 1946, Raymond Damadian constructing the first MRI scanner in 1977, and Paul Lauterbur and Peter Mansfield who developed techniques for spatial encoding and fast imaging in the 1970s. The document also outlines some of the basic physics principles behind MRI such as precession frequency, T1 and T2 relaxation times, and the use of gradient coils and RF pulses to encode spatial information and form images.
This document discusses the history and advancements of x-ray tubes and CT detectors. It describes how x-ray tubes have evolved from Roentgen's original design to current metal ceramic tubes used in spiral CT scanners. These CT x-ray tubes are able to provide continuous beams needed for CT imaging and have undergone improvements to handle increased heat, such as larger anodes and improved cooling. The document also contrasts gas ionization and scintillation detectors used to convert x-rays into electrical signals for CT imaging, noting advantages of each type.
This document provides an overview of MRI gradient echo pulse sequences, types, and applications. It discusses the basics of spatial encoding using slice selection, phase encoding, and frequency encoding gradients. It describes coherent gradient echo sequences which maintain transverse magnetization between excitations, and incoherent sequences which eliminate residual transverse magnetization. Spoiling techniques are discussed which remove signal from residual transverse magnetization to enhance T1 contrast. Applications include angiography, myelography and fast imaging where T1 or proton density contrast is desired.
This document describes a life detection system based on L-band microwave that can detect humans buried under rubble following disasters like earthquakes. The system uses microwaves in the L-band frequency range of 1-2 GHz, which can penetrate rubble up to 10 feet thick, to detect breathing and heartbeats of survivors. It is mounted on a drone and once it detects a survivor, it sends the coordinates to rescuers. This system provides a more effective solution than existing methods like sniffer dogs, cameras, or acoustic detectors, which cannot detect survivors deeper than a few feet under thick debris. While expensive, the cost could decrease with large-scale implementation. The system aims to reduce disaster death tolls by enabling faster
This document discusses various types of artifacts that can occur in MRI images and their causes and remedies. It covers technique-related artifacts such as chemical shift artifacts, Gibbs artifacts, aliasing artifacts, and magic angle artifacts. It also discusses patient-related artifacts like motion artifacts, metal artifacts, and flow artifacts. System-related artifacts discussed include shimming artifacts, gradient artifacts, and radiofrequency-related artifacts. For each type of artifact, the etiology, manifestation, and tips for remedying the artifact are provided. The document uses images to demonstrate examples of artifacts and their effects on MRI scans.
31P-MRSI of the brain with B1-shimmed NOE enhancement v6Bart van de Bank
This document describes the development of a 7T MRI coil setup to perform 31P MR spectroscopic imaging of the brain with B1-shimmed nuclear Overhauser effect signal enhancement. The coil setup includes an 8-channel 1H head coil for anatomical imaging and B1 field shimming, and a birdcage 31P coil with a 7-channel receive array to provide homogeneous excitation and increased signal-to-noise ratio through separate transmission and reception. Testing showed the receive array improved SNR by up to 700% and NOE enhancement increased the 31P-PCr signal by approximately 30%. The combined coil setup enables 3D 31P MRSI of the whole brain with enhanced spectral signals.
MEMS Approach to Low Power Wearable Gas SensorsMichael Lim
This presentation gives an overview of candidates solid state MEMS structures for wearable monitoring systems. The basic transduction mechanisms and device structures are shown for 5 types: QCM, FBAR, SAW, Cantilever, and CMUT. Finally, the structures are compared for their application into these mobile systems.
PARTICLE SEPARATION, CHEMICAL GRADIENT CONTROL AND MICROMIXING VIA FOCUSED TR...Ghulam Destgeer
1) The document discusses using focused travelling surface acoustic waves (F-TSAW) to separate particles, generate chemical gradients, and mix fluids in a microfluidic channel.
2) F-TSAW can continuously separate particles by size due to differences in acoustic radiation force and acoustic streaming flow effects. Chemical gradients are also generated through symmetrical owl's eye vortices created by acoustic streaming flow.
3) The presented F-TSAW microchip combines label-free particle separation, adjustable and rapidly switching chemical gradient generation, and uniform micromixing in a single portable device.
Surface Acoustic Wave Technology
Surface acoustic waves (SAW) propagate along the surface of piezoelectric materials and can be used to process signals. A SAW device consists of interdigital transducers (IDTs) and reflectors on a piezoelectric substrate that convert electrical signals to surface acoustic waves and vice versa. SAW devices are used in a wide range of applications including filters, sensors, and touchscreens. Touchscreens use SAW devices to detect touch locations by measuring wave absorption. SAW technology provides advantages such as low cost and power consumption but also has disadvantages like temperature dependence.
Surface acoustic wave (saw) radio transpondersRehan Fazal
A surface acoustic wave (SAW) radio transponder uses surface acoustic waves to enable remote sensing capabilities. SAW transponders consist of interdigital transducers that convert electromagnetic signals into acoustic waves that propagate along the surface of a piezoelectric material. These waves are then reconverted into electromagnetic signals by the transducers. SAW transponders are passive, wireless, and maintenance-free, making them well-suited for applications like temperature sensing on power lines. One key application is in tire pressure monitoring systems (TPMS), where the SAW device acts as a pressure sensor diaphragm to remotely measure tire pressure.
The document describes a new microwave life detection system that can locate human victims trapped under earthquake rubble. The system works by sending microwave beams through rubble at L-band frequency, which can penetrate deeper than other frequencies. Any signals reflected from a trapped victim's breathing and heartbeat movements would be detected. A clutter cancellation system filters out fixed reflections from rubble while preserving modulated signals from living beings. The system could help reduce loss of life from earthquakes by remotely detecting trapped humans within seconds.
Why Use SAW Sensors and Tags?
- Frequency/time are measured with greatest accuracy compared to any other physical measurement (10-10 - 10-14).
- External stimuli affects device parameters (frequency, phase, amplitude, delay)
- Operate from cryogenic to >1000oC
- Ability to both measure a stimuli and to wirelessly, passively transmit information
- Frequency range ~10 MHz – 3 GHz
- Monolithic structure fabricated with current IC photolithography techniques, small, rugged
Radiographic testing uses penetrating radiation directed at a component. Differences in how radiation is absorbed can be recorded on film or digitally to detect internal defects. There are various radiation sources and imaging methods used, including film, computed radiography, real-time radiography, and digital radiography. Strict safety protocols must be followed when using radiation to inspect components and ensure technician and public safety.
This document discusses and compares surface acoustic wave (SAW) devices and bulk acoustic wave (BAW) devices. SAW devices propagate waves along a material surface and are used in delay lines, filters, and other electronic components below 1 GHz. BAW devices propagate waves through the bulk material and can operate above 2 GHz in smaller sizes with less temperature sensitivity than SAW devices. Both SAW and BAW devices find applications in communications, radar, and other systems due to their filtering and signal processing capabilities.
The document provides an overview of the fundamentals of CT and MRI imaging. It discusses how CT was introduced in 1972 and revolutionized medical imaging by providing high-quality transverse cross-sectional images of the body without tissue superimposition. It also describes the evolution of CT technology from early generation pencil-beam systems to current helical CT scanners that acquire continuous data as the patient passes through the rotating gantry. Key developments included increasing the number of detectors to acquire wider beams, implementing rotating gantries to speed up scans, and incorporating slip-ring technology to allow continuous 360-degree rotation.
MRI uses magnetic fields and radio waves to produce detailed images of the brain and detect abnormalities. It is based on nuclear magnetic resonance, where hydrogen protons in the body are aligned by a strong magnetic field. When hit with radio waves of a specific frequency, the protons absorb energy and spin, and emit radio signals as they relax back to baseline. These signals are used to construct images, with different tissues appearing different intensities based on their relaxation times T1 and T2. MRI provides valuable information to assess many neurological conditions without using ionizing radiation.
Life Detection Using Microwaves TechnologySai Spandana
One of my first attempts to make a presentation. This presentation is based on a Research Article titled "A MODERN MICROWAVE LIFE DETECTION SYSTEM FOR
HUMAN BEING BURIED UNDER RUBBLE" published in the International Journal of Advanced Engineering Research and Studies
MRI image quality is affected by several factors including signal-to-noise ratio, receive bandwidth, noise sources, and spatial resolution. A higher signal-to-noise ratio provides better image quality. Receive bandwidth determines the range of frequencies received and affects chemical shift artifact and readout time. Noise in MRI comes from electronic noise and fluctuations in body tissues. Spatial resolution is influenced by receive bandwidth, matrix size, slice thickness, and field of view. Contrast resolution depends on tissue T1 and T2 values and the timing of pulse sequences. Motion contrast methods like diffusion weighting and flow weighting provide additional tissue information.
This is how we can save many life during any natural calamity like earthquake etc.., or if any building collapse then we can use this system which can detect the heart beats of those who are under the collapsed building.
The document discusses the parts and functioning of an x-ray machine. It is comprised of an x-ray tube, transformer, tube stand, and control panel. The x-ray tube produces electromagnetic radiation when electric current is supplied by the transformer. The images are recorded digitally on a computer after the radiation passes through the body. The document also provides a brief history of x-rays from their discovery in 1895 to the introduction of digital x-ray technology in 1997.
Radiography uses x-rays or gamma rays to detect flaws in materials. X-rays are produced when high-speed electrons collide with a metal target, while gamma rays come from radioactive isotopes. As the radiation passes through an object, areas of different thickness or density absorb differing amounts, forming an image on film or digitally. Radiography is widely used in industries like aerospace, military, and manufacturing to inspect components for defects without destroying them. Proper safety procedures must be followed due to the ionizing nature of x-rays and gamma rays.
X ray machines - conventional and digitalUrfeya Mirza
X-ray machines use high-energy electromagnetic radiation to generate digital or film images of the internal structures of objects. Conventional x-ray machines use film that must be developed, while digital x-ray machines directly convert x-rays to electrical signals and display images digitally. Both use an x-ray tube to generate x-rays, which are controlled via technique factors selected on the machine's control panel. Digital x-ray offers advantages like adjustable images and compatibility with digital record systems.
The document provides an overview of the history and development of magnetic resonance imaging (MRI) technology. It discusses several key figures who contributed discoveries that advanced MRI, such as Felix Bloch and Edward Purcell conducting the first NMR experiment in 1946, Raymond Damadian constructing the first MRI scanner in 1977, and Paul Lauterbur and Peter Mansfield who developed techniques for spatial encoding and fast imaging in the 1970s. The document also outlines some of the basic physics principles behind MRI such as precession frequency, T1 and T2 relaxation times, and the use of gradient coils and RF pulses to encode spatial information and form images.
This document discusses the history and advancements of x-ray tubes and CT detectors. It describes how x-ray tubes have evolved from Roentgen's original design to current metal ceramic tubes used in spiral CT scanners. These CT x-ray tubes are able to provide continuous beams needed for CT imaging and have undergone improvements to handle increased heat, such as larger anodes and improved cooling. The document also contrasts gas ionization and scintillation detectors used to convert x-rays into electrical signals for CT imaging, noting advantages of each type.
This document provides an overview of MRI gradient echo pulse sequences, types, and applications. It discusses the basics of spatial encoding using slice selection, phase encoding, and frequency encoding gradients. It describes coherent gradient echo sequences which maintain transverse magnetization between excitations, and incoherent sequences which eliminate residual transverse magnetization. Spoiling techniques are discussed which remove signal from residual transverse magnetization to enhance T1 contrast. Applications include angiography, myelography and fast imaging where T1 or proton density contrast is desired.
This document describes a life detection system based on L-band microwave that can detect humans buried under rubble following disasters like earthquakes. The system uses microwaves in the L-band frequency range of 1-2 GHz, which can penetrate rubble up to 10 feet thick, to detect breathing and heartbeats of survivors. It is mounted on a drone and once it detects a survivor, it sends the coordinates to rescuers. This system provides a more effective solution than existing methods like sniffer dogs, cameras, or acoustic detectors, which cannot detect survivors deeper than a few feet under thick debris. While expensive, the cost could decrease with large-scale implementation. The system aims to reduce disaster death tolls by enabling faster
This document discusses various types of artifacts that can occur in MRI images and their causes and remedies. It covers technique-related artifacts such as chemical shift artifacts, Gibbs artifacts, aliasing artifacts, and magic angle artifacts. It also discusses patient-related artifacts like motion artifacts, metal artifacts, and flow artifacts. System-related artifacts discussed include shimming artifacts, gradient artifacts, and radiofrequency-related artifacts. For each type of artifact, the etiology, manifestation, and tips for remedying the artifact are provided. The document uses images to demonstrate examples of artifacts and their effects on MRI scans.
31P-MRSI of the brain with B1-shimmed NOE enhancement v6Bart van de Bank
This document describes the development of a 7T MRI coil setup to perform 31P MR spectroscopic imaging of the brain with B1-shimmed nuclear Overhauser effect signal enhancement. The coil setup includes an 8-channel 1H head coil for anatomical imaging and B1 field shimming, and a birdcage 31P coil with a 7-channel receive array to provide homogeneous excitation and increased signal-to-noise ratio through separate transmission and reception. Testing showed the receive array improved SNR by up to 700% and NOE enhancement increased the 31P-PCr signal by approximately 30%. The combined coil setup enables 3D 31P MRSI of the whole brain with enhanced spectral signals.
The migration to IP has placed new demands on SCADA radio system capacity with equipment designers working to satisfy spectrum efficiency demands within economic constraints. Exciting new technologies have dramatically reduced the price of efficient quadrature amplitude modulation techniques to the point where implementation in moderately priced UHF SCADA radio systems is possible. This presentation will describe some of the technology behind a new low-cost digital radio that delivers 60 bps in 12.5 kHz for use in licensed UHF frequency bands with some discussion on application examples.
John Yaldwyn, Chief Technology Officer, 4RF Australia
This document provides information on building radiofrequency (RF) coils for magnetic resonance imaging (MRI). It discusses the key components of RF coils including inductors, capacitors and resistors. It describes different types of coil designs such as solenoid, surface, Helmholtz, birdcage and array coils. The document outlines the steps to build a basic loop coil including determining the loop size, measuring the inductance and tuning the coil to the desired resonance frequency. It also discusses matching the impedance of the coil to the MRI system and building quadrature and multi-nuclei coils. The learning objectives are to understand coil properties, types and how to develop a simple coil for MRI experiments.
The document discusses the fundamentals and work mechanism of magnetic resonance imaging (MRI). It introduces MRI as a medical instrument used to scan and image the inside of the body. The author's PhD focus and the increased demand for MRI exams are cited as reasons for choosing this topic. The aim is to familiarize the reader with the MRI machine and what happens inside during an exam by explaining its main parts, work mechanism, image processing, advantages, disadvantages, and predictions for future development.
Properties of coordination compounds part 2 of 3Chris Sonntag
1. Paramagnetism arises from unpaired electrons, which each have their own magnetic moment from both spin and orbital angular momentum.
2. Curie's Law describes how the magnetic susceptibility of a material depends on an external magnetic field and temperature, with higher magnetization occurring at higher fields and lower temperatures.
3. The Curie temperature is the point where a ferromagnetic material loses its permanent magnetism and becomes paramagnetic as spins become randomly oriented with increasing temperature.
The document discusses MRI safety guidelines regarding the strong magnetic fields and radiofrequency waves used in MRI. It outlines the basic components of MRI including the magnet and radiofrequency coils. It describes the different types of MRI magnets and important concepts like magnetic fringe fields, the 5 gauss limit and safety zones. The document provides screening guidelines for MRI and discusses potential hazards, risks and side effects of an MRI exam like acoustic noise, claustrophobia and effects of magnetic forces.
This document discusses various types of artifacts that can occur in MRI imaging, including equipment-related artifacts like non-uniform signal and phase wrap, as well as patient-related artifacts like susceptibility effects and motion blurring. It provides examples of static magnetic field (B0) inhomogeneity artifacts caused by differences in magnetic susceptibility between tissues. The document also discusses specific artifact reduction strategies, such as improving B0 field shimming, adjusting pulse sequence parameters like echo time, and using parallel imaging techniques to reduce geometric distortion from susceptibility effects. In summary, the document provides an overview of common MRI artifacts and their causes, with a focus on artifacts from magnetic field inhomogeneities and susceptibility differences between tissues.
MRI artifacts can occur due to hardware issues, software problems, physiological phenomena or physical limitations of the MRI device. Common artifacts include chemical shift artifacts seen at fat-water interfaces, aliasing artifacts due to an undersized field of view, black boundary artifacts at tissue borders, and motion artifacts from patient movement. Understanding the sources and appearances of artifacts is important for technicians to maintain image quality and avoid confusing artifacts with pathology.
The document summarizes common artifacts seen in MRI imaging including wrap around artifacts caused by a small field of view, partial volume artifacts from thick slices, chemical shift misregistration from misaligned water and fat signals, and motion-induced ghosts from patient movement during scanning. It provides examples and explanations of each artifact type as well as potential corrections.
MRI provides detailed images of the brain without exposing patients to radiation. It is useful for evaluating conditions like tumors, strokes, and multiple sclerosis. The document describes the MRI procedure for brain imaging including patient preparation, head coils, sequences, and protocols. Key sequences discussed are T1-weighted, T2-weighted, FLAIR, diffusion weighted, MR angiography, and MR venography.
MRI Scanner, Instrumentation. MDIRT ST. Louis Bamenda, Nchanji Nkeh KenethNchanji Nkeh Keneth
The MRI Scanner; historical facts, Understanding Nuclear Magnetic Resonance, The Scanner componenets, Radiofrequency coils, the casing, types of MRI magnets, understanding the principle of superconductivity. MRI applications
An inexpensive embedded system was designed and developed to measure magnetic fields for low frequency nuclear magnetic resonance (NMR) applications. The system uses a Hall effect sensor to accurately measure magnetic fields. It is connected to a microcontroller with an analog-to-digital converter to convert the sensor output voltage to measured magnetic field values in Gauss. The system was able to successfully measure different magnetic fields and provides a low-cost option for NMR applications requiring magnetic field measurements.
MRI artifacts can be caused by patient movement, hardware issues, chemical shifts, and other sources. They appear as features not present in the original object and can hinder diagnosis. Common artifacts include motion artifacts from respiration or flow, chemical shift artifacts at fat-water interfaces, and susceptibility artifacts near metal. Understanding the physics behind each artifact and methods for correction, such as changing sequences or saturation bands, helps improve image quality.
This document provides an overview of magnetic resonance imaging (MRI). It discusses the history of MRI, including key contributors like Felix Bloch and Edward Purcell. It describes the main components of an MRI machine, including the main magnet, gradient coils, RF coils, shielding, and computers. It explains the physics principles behind MRI such as magnetic fields, precession, relaxation, and gradients. It also covers MRI signal types, sequencing, tissue contrast, image quality, artifacts, and safety considerations.
This document summarizes a study that used a new technique called noise-immune cavity-enhanced optical heterodyne velocity modulation spectroscopy (NICE-OHVMS) in the mid-infrared region to perform sub-Doppler spectroscopy on molecular ions. The researchers implemented NICE-OHVMS using a tunable optical parametric oscillator in the 3.2-3.9 μm range. As a demonstration, they recorded spectra of the m2 fundamental band of H3+ ions at 3.67 μm. The high optical power and cavity enhancement allowed line center frequencies to be measured with a precision of 70 kHz, demonstrating the capabilities of this new mid-infrared NICE-OHVMS instrument.
The document provides a brief history of radiation therapy and x-rays, including their discovery in the late 19th century, and developments in equipment over time. It discusses early radiation therapy methods like orthovoltage and kilovoltage treatments. It also summarizes linear accelerators and how they improved upon older cobalt-60 and betatron technology to allow higher energy photon beams for treating deeper tumors. Simulation equipment is covered, comparing conventional versus CT-based simulation and how various imaging modalities can aid treatment planning.
Modalities such as X-ray, CT, ultrasound, nuclear medicine, and MRI provide different types of anatomical and functional medical imaging. X-ray and CT measure attenuation coefficients, ultrasound measures acoustic reflectivity, nuclear medicine provides functional imaging using radioactive tracers, and MRI uses magnetic fields to produce multiparametric images related to proton density and relaxation times. Each modality has strengths and limitations for different clinical applications depending on safety, image quality, and other factors. The economics of medical imaging require significant capital investments and operational costs to support clinical services.
This document discusses MRI safety. It provides an overview of the MRI system, including the static magnetic field, radiofrequency field, and gradient magnetic field. It outlines several safety risks associated with the MRI environment, such as the projectile effect of ferromagnetic objects, tissue burns from RF heating, high acoustic noise levels, and nerve stimulation. The document emphasizes the importance of MRI safety screening and procedures to mitigate risks. It aims to educate staff on key safety issues and their roles in ensuring safe practice in the MRI environment.
2019-06-07 Characterization and research of semiconductors with an FTIR spect...LeonidBovkun
2019-06-07 Educational seminar at EP-3 University of Wuerzburg
I will present particular experiments and related results with FTIR spectrometer, so one may consider these experiments complimentary for you research.
MRI uses powerful magnets and radio waves to generate detailed images of the inside of the body. It has several key components, including a superconducting magnet that provides a strong magnetic field, gradient coils that vary the field to provide positional information, and RF coils that transmit pulses to excite protons and receive their signals. To function properly, the superconducting magnet must be cooled to very low temperatures using liquid helium, and advanced cooling systems like laser cooling are being developed and researched. The computer system digitizes the received signals and applies transformations to construct images that can reveal soft tissue structures and abnormalities.
MRI uses strong magnetic fields and radio waves to produce detailed images of the inside of the body without using ionizing radiation. It works by aligning hydrogen atoms in the body using magnetism and radio waves, and detecting the radio signals emitted as the atoms relax back to their normal state. This allows physicians to see detailed soft tissue structures. MRI is useful for diagnostic and research purposes such as locating tumors, assessing tissue conditions, and studying brain function.
1) The document discusses ultrashort pulse (USP) laser interactions with matter, including microresonator-based optical frequency combs, high peak power laser processing of materials, and extreme ultraviolet comb spectroscopy.
2) It outlines several research initiatives exploring topics like dynamics of microresonator comb generation, laser ablation mechanisms with ultrashort pulses, and dual comb spectroscopy in the extreme ultraviolet.
3) The document also covers applications of USP lasers in metrology, material science, and particle acceleration, and research into relativistic laser-matter interactions generating bright x-ray sources.
Magnetic resonance imaging (MRI) uses strong magnetic fields and radio waves to generate images of the body's internal structures. While MRI is generally safe, certain safety considerations must be addressed regarding the static magnetic field, time-varying gradient magnetic fields, and radiofrequency fields used. Key risks include attraction of ferromagnetic objects, acoustic injury from loud noises, and heating of tissues from radiofrequency exposure. Guidelines limit exposure levels and recommend screening patients for implants to ensure safe MRI examinations.
This document provides an overview of various medical imaging modalities including their physics principles, capabilities, limitations and artifacts. It discusses x-rays/radiography, CT, and MRI. For each modality, it explains how images are generated, advantages, limitations including radiation dose for CT and need for patient cooperation/stillness for MRI. It emphasizes understanding limitations to avoid "wishful thinking" and making diagnoses from suboptimal studies.
This document summarizes several abstracts presented at the AIP Bi-Annual Postgraduate Conference on September 7-8, 2001. The abstracts covered topics related to gravitational waves, opto-acoustic interactions, quantum mechanics, spin waves, frequency sources, phonon lasers, nanostructure fabrication, and silicon nanowire growth. Experimental and theoretical work was presented across various fields of physics including general relativity, quantum physics, condensed matter physics, and nanotechnology.
FT-NMR spectrometry works by applying pulses of radio frequency energy to excite nuclei in a sample simultaneously, rather than continuously scanning individual frequencies. This allows the free induction decay signal to be recorded over time and converted to a frequency spectrum using Fourier transforms. FT-NMR provides higher sensitivity than continuous wave NMR, allowing analysis of smaller sample sizes, and faster acquisition of spectra in seconds rather than minutes. The technique was pioneered by Richard R. Ernst, who won the Nobel Prize in Chemistry in 1991 for his contributions to the development of FT-NMR and multi-dimensional NMR spectroscopy.
This document provides an overview of magnetic resonance imaging (MRI) including:
1. The history and timeline of MRI development from the 1920s to present day. Key developments include the discoveries of nuclear magnetic resonance and techniques for generating MRI images using gradients.
2. The basic components and principles of how MRI works including strong magnets, gradient coils, radiofrequency coils, spin precession, relaxation times, and Fourier transforms to generate images.
3. Explanations of fundamental MRI sequences including T1-weighted, T2-weighted images and how contrast is achieved using repetition time and echo time.
4. Clinical applications of MRI including its advantages over other imaging modalities as well as some disadvantages and
Microwaves are electromagnetic waves with frequencies between 300MHz- 300GHz. Microwave communication uses microwave towers to transmit signals over long distances via line-of-sight. Key applications of microwaves include communication systems, satellite systems, radar for target detection, microwave heating for cooking and industrial processes, and microwave spectroscopy for materials analysis. Microwaves have advantages over lower frequencies including smaller antenna size, ability to penetrate some materials, and providing larger bandwidth for more channels in communication.
TU1.L09 - RECENT ADVANCES IN FULLY POLARIMETRIC SPACE-SAR SENSOR DESIGN AND I...grssieee
The document discusses the need for multi-modal, multi-band polarimetric interferometric synthetic aperture radar (POLinSAR) satellite systems for monitoring the Earth. It analyzes how POLinSAR can provide information that polarimetric SAR and interferometric SAR alone cannot by combining data from multiple passes. It argues that such systems are urgently required to monitor population growth and reduce conflicts by enabling continuous global monitoring of the biosphere, atmosphere, hydrosphere and impacts like pollution, natural disasters, and climate change. Examples of POLinSAR data from existing satellites like ALOS are presented to demonstrate techniques like scattering decomposition.
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.
Similar to Dr. Simone A Winkler - Ultra High-Field MRI Open Questions in Engineering and Multiphysics (20)
Determination of Equivalent Circuit parameters and performance characteristic...pvpriya2
Includes the testing of induction motor to draw the circle diagram of induction motor with step wise procedure and calculation for the same. Also explains the working and application of Induction generator
We have designed & manufacture the Lubi Valves LBF series type of Butterfly Valves for General Utility Water applications as well as for HVAC applications.
A high-Speed Communication System is based on the Design of a Bi-NoC Router, ...DharmaBanothu
The Network on Chip (NoC) has emerged as an effective
solution for intercommunication infrastructure within System on
Chip (SoC) designs, overcoming the limitations of traditional
methods that face significant bottlenecks. However, the complexity
of NoC design presents numerous challenges related to
performance metrics such as scalability, latency, power
consumption, and signal integrity. This project addresses the
issues within the router's memory unit and proposes an enhanced
memory structure. To achieve efficient data transfer, FIFO buffers
are implemented in distributed RAM and virtual channels for
FPGA-based NoC. The project introduces advanced FIFO-based
memory units within the NoC router, assessing their performance
in a Bi-directional NoC (Bi-NoC) configuration. The primary
objective is to reduce the router's workload while enhancing the
FIFO internal structure. To further improve data transfer speed,
a Bi-NoC with a self-configurable intercommunication channel is
suggested. Simulation and synthesis results demonstrate
guaranteed throughput, predictable latency, and equitable
network access, showing significant improvement over previous
designs
Null Bangalore | Pentesters Approach to AWS IAMDivyanshu
#Abstract:
- Learn more about the real-world methods for auditing AWS IAM (Identity and Access Management) as a pentester. So let us proceed with a brief discussion of IAM as well as some typical misconfigurations and their potential exploits in order to reinforce the understanding of IAM security best practices.
- Gain actionable insights into AWS IAM policies and roles, using hands on approach.
#Prerequisites:
- Basic understanding of AWS services and architecture
- Familiarity with cloud security concepts
- Experience using the AWS Management Console or AWS CLI.
- For hands on lab create account on [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
# Scenario Covered:
- Basics of IAM in AWS
- Implementing IAM Policies with Least Privilege to Manage S3 Bucket
- Objective: Create an S3 bucket with least privilege IAM policy and validate access.
- Steps:
- Create S3 bucket.
- Attach least privilege policy to IAM user.
- Validate access.
- Exploiting IAM PassRole Misconfiguration
-Allows a user to pass a specific IAM role to an AWS service (ec2), typically used for service access delegation. Then exploit PassRole Misconfiguration granting unauthorized access to sensitive resources.
- Objective: Demonstrate how a PassRole misconfiguration can grant unauthorized access.
- Steps:
- Allow user to pass IAM role to EC2.
- Exploit misconfiguration for unauthorized access.
- Access sensitive resources.
- Exploiting IAM AssumeRole Misconfiguration with Overly Permissive Role
- An overly permissive IAM role configuration can lead to privilege escalation by creating a role with administrative privileges and allow a user to assume this role.
- Objective: Show how overly permissive IAM roles can lead to privilege escalation.
- Steps:
- Create role with administrative privileges.
- Allow user to assume the role.
- Perform administrative actions.
- Differentiation between PassRole vs AssumeRole
Try at [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
Supermarket Management System Project Report.pdfKamal Acharya
Supermarket management is a stand-alone J2EE using Eclipse Juno program.
This project contains all the necessary required information about maintaining
the supermarket billing system.
The core idea of this project to minimize the paper work and centralize the
data. Here all the communication is taken in secure manner. That is, in this
application the information will be stored in client itself. For further security the
data base is stored in the back-end oracle and so no intruders can access it.
Blood finder application project report (1).pdfKamal Acharya
Blood Finder is an emergency time app where a user can search for the blood banks as
well as the registered blood donors around Mumbai. This application also provide an
opportunity for the user of this application to become a registered donor for this user have
to enroll for the donor request from the application itself. If the admin wish to make user
a registered donor, with some of the formalities with the organization it can be done.
Specialization of this application is that the user will not have to register on sign-in for
searching the blood banks and blood donors it can be just done by installing the
application to the mobile.
The purpose of making this application is to save the user’s time for searching blood of
needed blood group during the time of the emergency.
This is an android application developed in Java and XML with the connectivity of
SQLite database. This application will provide most of basic functionality required for an
emergency time application. All the details of Blood banks and Blood donors are stored
in the database i.e. SQLite.
This application allowed the user to get all the information regarding blood banks and
blood donors such as Name, Number, Address, Blood Group, rather than searching it on
the different websites and wasting the precious time. This application is effective and
user friendly.
Impartiality as per ISO /IEC 17025:2017 StandardMuhammadJazib15
This document provides basic guidelines for imparitallity requirement of ISO 17025. It defines in detial how it is met and wiudhwdih jdhsjdhwudjwkdbjwkdddddddddddkkkkkkkkkkkkkkkkkkkkkkkwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwioiiiiiiiiiiiii uwwwwwwwwwwwwwwwwhe wiqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq gbbbbbbbbbbbbb owdjjjjjjjjjjjjjjjjjjjj widhi owqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq uwdhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhwqiiiiiiiiiiiiiiiiiiiiiiiiiiiiw0pooooojjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj whhhhhhhhhhh wheeeeeeee wihieiiiiii wihe
e qqqqqqqqqqeuwiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiqw dddddddddd cccccccccccccccv s w c r
cdf cb bicbsad ishd d qwkbdwiur e wetwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww w
dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddfffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffw
uuuuhhhhhhhhhhhhhhhhhhhhhhhhe qiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii iqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc ccccccccccccccccccccccccccccccccccc bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbu uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuum
m
m mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm m i
g i dijsd sjdnsjd ndjajsdnnsa adjdnawddddddddddddd uw
Build the Next Generation of Apps with the Einstein 1 Platform.
Rejoignez Philippe Ozil pour une session de workshops qui vous guidera à travers les détails de la plateforme Einstein 1, l'importance des données pour la création d'applications d'intelligence artificielle et les différents outils et technologies que Salesforce propose pour vous apporter tous les bénéfices de l'IA.
SENTIMENT ANALYSIS ON PPT AND Project template_.pptx
Dr. Simone A Winkler - Ultra High-Field MRI Open Questions in Engineering and Multiphysics
1. STANFORD
UHF MRI
PROGRAM
ULTRA HIGH-FIELD MRI
OPEN QUESTIONS IN ENGINEERING AND
MULTIPHYSICS
SIMONE A. WINKLER, PH.D.
MCGILL UNIVERSITY | 2014/04/16
Department of Radiology
Stanford University
ETH Zürich | 2014/12/19S. A. WINKLER
3. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
STANFORD RADIOLOGICAL SCIENCES LABORATORY
JOHANNES KEPLER UNIVERSITY LINZ | 2014/05/08S. A. WINKLER
• Three 3T GE whole-body MR
systems (one being the first
GE PET-MR)
• One 7T GE whole-body MR
system
Gary
Glover
Brian
Hargreaves
Daniel
Spielman
Brian
Rutt
Rebecca
Fahrig
Michael
Moseley
Norbert
Pelc
Jennifer
McNab
Roland
Bammer
Kim Butts
Pauly
5. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MR BASICS – NUCLEAR MAGNETIC RESONANCE
Isotopes in the body with odd number of protons possess nonzero spin
moving electrons generate small magnetic field
Hydrogen atoms most abundant in human body (tissue water content)
JOHANNES KEPLER UNIVERSITY LINZ | 2014/05/08S. A. WINKLER
TWO-STEP PROCEDURE:
1. Alignment (polarization) of spins with an external static magnetic
field B0
2. Perturbation of alignment by use of an RF (electromagnetic) field
magnetization of protons can be measured
6. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MR BASICS – STEP 1: SPIN ALIGNMENT
JOHANNES KEPLER UNIVERSITY LINZ | 2014/05/08S. A. WINKLER
Without
external
B0-field
With
external
B0-field
Larmor frequency
depends on magnetic
properties of proton,
and is proportional to
static magnetic field
strength
Spin precession
at Larmor
frequency
Alignment Precession
No net magnetization
7. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
Transverse
component
can be
detected with
an RF coil!
MR BASICS – STEP 2: PERTURBATION/MEASUREMENT
JOHANNES KEPLER UNIVERSITY LINZ | 2014/05/08S. A. WINKLER
excitationrelaxation
RF excitation:
Additive B1 pulse
in transverse
plane at Larmor
frequency
T2 T1
Precession at Larmor Frequency Added RF pulse at Larmor frequency
Tissue contrast:
RF coil
transceive
s
transverse
magnetic
field
B1
B0
Idea: measure magnetic field that spin generates!
B0
After RF pulse is turned off:
8. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MR BASICS – SPATIAL LOCALIZATION
Larmor frequency depends on static magnetic field strength
Small magnetic field variation is overlaid depending on location of imaged
voxel
frequency of received signal contains spatial information!
JOHANNES KEPLER UNIVERSITY LINZ | 2014/05/08S. A. WINKLER
With linear additive
gradient:
Spatial information can be
recovered from Inverse
Fourier Transform!!
3Dlocalization
Gradient coils
DC current generates
linear B0 variation
9. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MR BASICS - SYSTEM
Main system components:
1. Magnet (generates B0
field aligns spins net
magnetization)
2. RF coil (excites and
receives RF magnetic
field at Larmor frequency)
3. Gradient coils (localization
by small variation of B0
field)
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Typical B0 field strengths (human):
Clinical: 1.5T-3T
Research: 7T-11.7T
10. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
WHY UHF MRI?
Increased sensitivity for proton imaging applications (SNR
increases approx. proportionally with B0)
Allows for anatomical imaging with higher spatial resolution
Use higher sensitivity to examine dynamic and functional
aspects (BOLD, other brain activity)
ETH ZÜRICH | 2014/12/19S. A. WINKLER
7T
• Potential for detection
of new physiology of
healthy and diseased
tissue
• New forms of contrast
Energy gap:
12. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
HARDWARE RELATED UHF MRI CHALLENGES
Global SAR increases with B0
2
Local SAR becomes more inhomogeneous due to
wave effects
Local SAR is strongly position- and coil-
dependent
ETH ZÜRICH | 2014/12/19
RF heating in tissue
(SAR)
B1 inhomogeneities
Lorentz ForcesB0 inhomogeneities
128MHz 512MHz
Larmor frequency
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
-0.2
-0.15
-0.1
-0.05
0
0.05
W/kg
0.57
1.14
1.71
2.28
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
-0.2
-0.15
-0.1
-0.05
0
0.05
W/kg
0.57
1.14
1.71
2.28
2.25
0
W/kg
Image shading Patient safety
Acoustics &
Vibrations
Geometric distortion
& artefacts
Lorentz forces increase with
B0
Higher sound pressure levels
Stronger vibrations
Spatial encoding
depends on B0
homogeneity
Signal loss
13. STANFORD
UHF MRI
PROGRAM
IMAGE SHADING – B1 INHOMOGENEITY
OPTIMIZED DIELECTRIC SHIMMING – SIMONE WINKLER, ALESSANDRO SBRIZZI, ET AL.
16-CHANNEL PTX COIL DESIGN – RICCARDO STARA, SIMONE WINKLER, ET AL.
ETH Zürich | 2014/12/19S. A. WINKLER
14. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
B1 INHOMOGENEITY BASICS
Parallel Transmission (pTx):
excitation from multiple
independent channels with different
pulse signal shapes at each
channel
RF shimming: excitation from
multiple independent channels; only
amplitude and phase are varied
Dielectric shimming: passive
perturbation of E- and B-fields by
insertion of dielectric material that
focuses field lines
ETH ZÜRICH | 2014/12/19S. A. WINKLER
128MHz 512MHz
Larmor frequency
Remedy:Challenge:
15. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
16-CHANNEL PTX COIL DESIGN
1. Novel coil element 2. Modular configuration
1. 8ch single row
2. 8ch checkerboard
3. 16ch with two Butler matrices
4. 8ch with Butler matrix
5. 2ch with Butler matrix
6. etc.
Inherent inter-element decoupling
B1 mapsZ-segmentation
1 2
3 4COAX4
ID=CX2
EL=90 Deg
Fo=0.1 GHz
Z=50
IND
ID=L1
L=580 nH
CAPQ
ID=C1
C=24 pF
Q=0
FQ=0 GHz
ALPH=1
CAPQ
ID=C2
C=10 pF
Q=0
FQ=0 GHz
ALPH=1
T
1
2
REST
ID=IN1
R=1-5 Ohm
T=-273.15 DegC
IND
ID=L2
L=80 nH
DIODE1
ID=Microsemi HUM2015
Nu=0
T=21.85 DegC
Io=0 mA
CAPQ
ID=C3
C=10 pF
Q=0
FQ=0 GHz
ALPH=1
CAP
ID=C4
C=0-1 pF
PORT
P=1
Z=50 Ohm
PORT
P=2
Z=50 Ohm
CT1
CT2
Coil
CM
TuningMatching
RF choke
Decoupling
• Illumination of
lower brain regions
• Better acceleration
• Better pTx
flexibility
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Inter-element coupling
3. 3D segmentation Results
16. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
OPTIMIZED DIELECTRIC SHIMMING
Electromagnetic scattering is ANALYTICALLY described for dielectric-
absorptive spheres! [1]
model dielectric pad as a sphere!
Model head as a dielectric sphere
Model dielectric shimming pads as additional spheres
Optimization to determine optimized position of the sphere(s)
Requirement:
Electromagnetic fields of unloaded RF coil expanded into
vector spherical harmonics
S. A. WINKLER
[1] Gustav Mie, ”Beiträge zur Optik trüber Medien, speziell kolloidaler Metallösungen,“ Annalen der Physik, Vierte Folge, Band 25, 1908, No. 3, p 377-445.
[2] M. I. Mishchenko, L. D. Travis, and D. W. Mackowski, T-matrix computations of light scattering by nonspherical particles: A review, J. Quant. Spectrosc. ETH ZÜRICH | 2014/12/19
Improvement:
41.25%
Dielectric
shimming
also
increases
average B1+
field!
Applications:
• 3T breast MR
• 7T neuroimaging
18. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
B0 INHOMOGENEITY BASICS
B0 field has to be extremely homogeneous (order of
ppm, for 7T in the 0.25μT range)
Spatial encoding depends on B0 homogeneity
Geometric distortions and/or signal loss
Sources of B0 inhomogeneity:
1. Magnet construction
2. Magnetic susceptibility differences
in tissues; in particular:
air cavities (ears, sinuses, etc.)
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Remedy:Challenge:
7.00001
6.99999
7.00000
B0 shimming:
Air cavities
water
Passive
Active
Spherical
harmonic
s
Matrix
shim
Iron
inserts
19. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
HISTORY
High-order B0 shimming is essential for modern MR neuroimaging
Conventional approach: spherical harmonic shimming
ISMRM 2015 TORONTO, CANADA | 2015/06/04S. A. WINKLER
Multi-Coil Shimming Multi-Coil + RF shimming
Alternative to spherical harmonic
shimming
+ Efficient
+ Switch shim dynamically without eddy
currents
- Restricted space for RF arrays
- Interactions with RF coils
Uses RF chokes to bridge DC shim
current into RF loop
+ Larger efficiency due to single-turn
loop
+ Dynamic switching
- Construction complexity
Juchem C, JMR 212:280–288 (2011) Truong TK, Neuroscience 103:235-240 (2014)
7T 3TDrastic B0 homogeneity improvements
20. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
RF-SHIM HELMET - CONCEPT
ISMRM 2015 TORONTO, CANADA | 2015/06/04S. A. WINKLER
RF-Shim Helmet - Concept:
32chRF-shimcoil
32chRF-onlycoil
Conventional RF coil Shim-RF coil
Coilelement
Combining Rx (RF) and B0 (DC)
shimming functions on the same
conductor
Array of single-turn loops
Helmet shape for closer proximity
(increased Rx SNR and B0 shim efficiency)
+
Stockmann, MRM early view (2015)
Chokes to bridge
capacitor breaks
RF-path only Added DC path
3T
21. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
RF-SHIM HELMET - RESULTS
ISMRM 2015 TORONTO, CANADA | 2015/06/04S. A. WINKLER
z
Rx-Shim Helmet – 3T Results:
B0 – shimming results:
32ch commercial c32ch RF-shim coil
SNRCoilcorrelation
Precursor 32ch coil
a.u.
32ch commercial coil32ch RF-shim coil
0
100
200
300
400
SNRCoilcorrelation
Precursor 32ch coil
0
1
0.5
RF - SNR results:
RF-shim coil exhibits modest
SNR loss as compared to
precursor RF-only coil
Stockmann, MRM early view (2015)
+ Reduced distortion and closer alignment for blip-up and blip-
down
+ Predicted and measured field maps agree
+ Low current requiremnts (2.5 A max per coil)
22. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
RF-SHIM CONCEPT AT 7T
Using the RF-shim concept at 7T appears compelling:
1. Increased in-vivo B0 distortion at 7T greater impact for
• EPI (fMRI, Diffusion)
• QSM
• Inversion pulses
2. SNR impact at 7T might be lower
• A well designed receive array is body noise dominated
• We hypothesize that at 7T added copper noise will have less impact
However:
Conversion from 3T RF-only to RF-shim array caused 10-
15% SNR loss
We seek to minimize SNR loss at 7T
ISMRM 2015 TORONTO, CANADA | 2015/06/04S. A. WINKLER
Optimized loop design
becomes essential
The resulting 7T RF-
shim array would offer:
- Helmet design for
SNR and shim
efficiency
- Minimal interference
of RF and shim
functions
Optimized compact tool for
modern high-field MR
neuroimaging
Here: Exploratory work to choose optimized loop design
23. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MOTIVATION
ISMRM 2015 TORONTO, CANADA | 2015/06/04S. A. WINKLER
Larger number of capacitors
required for 7T larger
number of toroidal bridging
chokes
Challenges:
Coaxial loop
element
Novel combined conductor concepts:
Concentric loop element
- Inner conductor:
DC shim current
- Outer conductor
(RF shield):
RF current
- Inner loop:
DC shim current
- Outer loop:
RF current
Reduced number of capacitors
No chokes required
• Additional loss
• Heating
• RF field perturbation
• Construction complexity in
confined space
Magnetic coupling between conductors lowers self-inductance of RF loopChokes
DC
path
DC
path
24. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
THEORY
Magnetic coupling between inner and outer conductor
Two conjugate poles
Two conjugate zeroes
ISMRM 2015 TORONTO, CANADA | 2015/06/04S. A. WINKLER
Resonance + anti-resonance
𝑓𝑟,shim
𝑓𝑟,standalone
=
1
1 − 𝑘2 k = inter-loop coupling factor
𝑓𝑎𝑟,shim
𝑓𝑎𝑟,standalone
=
1
1 + α2
Resonance:
Anti-resonance:
α =
𝐿 𝑠
𝐿 𝑅𝐹
−
2𝐿 𝑚
𝐿 𝑅𝐹
LS = shim loop inductance
LRF = RF loop inductance
Lm = mutual inductance
Trade-off between
Q-factor reduction
and number of
capacitors to be
found
Coaxial loop
element
Concentric
loop element
Effects of added loop:
1. Resonance frequency increases
because of lowered self inductance
2. Added loop acts as a resistive load
in time-quadrature to the original
loop
+ Fewer capacitors are required
(and therefore bridging chokes)
- Reduction in Q-factor (and thus
SNR) by insertion of additional
loop
25. STANFORD
UHF MRI
PROGRAM
MR SAFETY
THERMOACOUSTIC SAR MAPPING – SIMONE WINKLER, PAUL PICOT, MICHAEL THORNTON,
BRIAN RUTT
SAR-CONSTRAINED PTX PULSE DESIGN – MIHIR RAJENDRA PENDSE, SIMONE WINKLER, BRIAN
RUTT
ETH Zürich | 2014/12/19S. A. WINKLER
26. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MR SAFETY BASICS
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Main concern: RF power deposition in tissue (metric: specific absorption rate (SAR))
Low field MRI:
Wave effects are not prominent and local SAR is therefore easier to predict
High-field MRI:
1. SAR increases with B02
2. variation in tissue properties AND fields strong variations in local SAR –
SAR is strongly dependent on:
o Patient
o Coil
o Position
3. pTx techniques may cause worst-case constructive interference of individual
local SAR patterns great concerns!
To date there is no
experimental procedure
to measure local SAR!
RF power deposition over
entire anatomy of interest
Global SAR
local variation of SAR that
leads to prominent
hotspots
Local SAR
IEC regulation:
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
-0.2
-0.15
-0.1
-0.05
0
0.05
W/kg
0.57
1.14
1.71
2.28
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
-0.2
-0.15
-0.1
-0.05
0
0.05
W/kg
0.57
1.14
1.71
2.28
2.25
0
W/kg
3.2 W/kg 10 W/kg
Alternative metric:
temperature in tissue (max.
1°C heating)
• SAR-minimized pTx
pulse design
• Find methods to
experimentally
determine SAR
• Find alternative
metric
(temperature)
Remedy:Challenge:
27. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
SAR-MINIMIZED PTX PULSE DESIGN
ETH ZÜRICH | 2014/12/19S. A. WINKLER Pendse, Winkler and Rutt, ISMRM 2014
B1 mapping
MR scan
Localizer Query database for body
model matching patient
Anatomical
parameters
minSAR pTx scan
minSAR
RF Pulse
Optimize pulse
sequence
parameters
minSAR
MLS
Local SAR
dependent
Local SAR
independent
RF Pulse Design
Non pTx
scanning
E-field maps VOPs
…
Body models
SAR database (computed offline)
EM simulationofflinereal-time
Compressed
dataset
28. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
THERMOACOUSTIC SAR CONCEPT
ETH ZÜRICH | 2014/12/19S. A. WINKLER
IDEA:
absorbed RF energy ≡ SAR!
MR RF coil as RF transmitter generates same local
SAR pattern as in an MR scan
RF-induced thermoacoustic signal is proportional
to local SAR use MR coil with short bursts of RF
energy
𝛻2 −
1
𝑣𝑠
2
𝜕2
𝜕𝑡2
𝒑 = −
𝛽𝜌
𝐶 𝑝
𝐒𝐀𝐑 𝐫
𝜕𝐼
𝜕𝑡
Pulsed RF absorptionAcoustic pressure wave
US patent: Simone Winkler, Brian Rutt, Paul Picot, Michael Thornton. “In-Vivo Specific Absorption Rate
Mapping using the Thermoacoustic Effect", May 7, 2014
30. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
TEST PLATFORM
Proof of concept with thermoacoustic
imaging platform at Stanford
(collaboration with Endra, Inc.)
S. A. WINKLER
By varying
1. Conductivity
2. Electric Field
in a phantom, we can emulate the
local SAR variation in tissue in UHF
MRI
1) OriginalTan
k
A
B
0°
2) One excitation
channel off
Tan
k
A
X
Agar (σ = 0)
Saline
1.25%
2.25%
3.75%
5%
1 – conductivity variation 2 – E-field variation
5%
3%
2.25%
1.25%
Point source experiments
E-Fieldvariation
RF horns
Ultrasound
transducer
31. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
EXPERIMENTS – FIRST ATTEMPT
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Agar (σ = 0)
Saline
1.25%
2.25%
3.75%
5%
Varying conductivity:
Concen-
tration
Image
value
1.25% 536±91
2% 876±125
2.25% 960±65
3.75% 1768±353
5% 2423±254
ThermoacousticImage
0
500
1000
1500
2000
2500
3000
0.00% 2.00% 4.00% 6.00%
Image value over
saline concentration
32. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
POINT SOURCE EXPERIMENTS – OVERALL SAR VARIATION
S. A. WINKLER
R² = 0.5224
R² = 0.8458
0
2
4
6
8
10
12
0 2 4 6 8 10
Horizontal SAR
Vertical SAR
Linear (Horizontal SAR)
Linear (Vertical SAR)
Tan
k
A
X
Tan
k
A
B
0°
5%
3%
2.25%
1.25%
2.25%
2.25%
2.25%
2.25%
Conductivity variation
Constant
conductivity
Varied
conductivity
E-Field variation
+ rotated
ultrasound
transducer
to average
over
perceived E-
field
Without
rotation to
maximize E-
field
variation
E-field was
measured with a
coaxial probe
Reference test
SAR variation
E-Fieldvariation
Conduc-
tivity
variation
Conductivity
variation
Conductivity
variation
E-Fieldvariation
UStransducer
RF
horn
Image values fitted to
SAR equation:
33. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MR SYSTEM INTEGRATION
Fast rise-time pulse shape
required MR system might have
to be upgraded with a larger
bandwidth auxiliary signal
generator
It is estimated that the power
amplifier of the MR system will be
delivering sufficient peak power for
the experiment
An ultrasound bandwidth of 200
kHz will be used for penetrating
skull bone
Ultrasound transducers will be
mounted at two lateral acoustic
windows in the skull
S. A. WINKLER
Power
amplifier
MR
signal
generato
rAuxiliary
signal
generato
r
Control
room
workstatio
n
Data
acquisition
system
Patient head
Ultrasoun
d
transduce
r
RF
coil
34. STANFORD
UHF MRI
PROGRAM
MR ACOUSTICS
UHF-MRI ACOUSTICS IN HEAD AND BODY GRADIENTS – SIMONE
WINKLER, TREVOR WADE, ANDREW ALEJSKI, CHARLES MCKENZIE,
BRIAN RUTT
ETH Zürich | 2014/12/19S. A. WINKLER
35. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
HEAD GRADIENT INSERT
ETH ZÜRICH | 2014/12/19
Smaller field of linear region (approx. 20
cm)
Higher slew rate
Higher gradient strength (100 – 300 mT/m)
Inserted into bore
190
170
220
450
490 338
Body gradient coil Head gradient insert coil
Faster or higher resolution imaging
Large linear region (60 cm)
Low slew rate
Low gradient strength (50 – 80 mT/m)
Built into MR system
• Attractive at
high field
• Louder
acoustics
36. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
FUNDAMENTALS OF VIBROACOUSTICS
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Time-
varying
pressure
inside bore
Structural
vibration of
gradient coil
B0
.
F(t)
i(t)
Fundamentals:
Time-varying
current in gradient
conductor, in
presence of strong
B0 field, causes
Lorentz forces
Structur
e
Flui
d
(air)
vibrations
Pressure change = sound wave
Structural vibrations:
n=0 n=1
n=2 n=3
Breathing Bending
Ovaling
Acoustic coupling:
structure modes in the coil
structure
acoustic modes in the coil
bore
Interaction
MUTUAL
COUPLING!
Avg displacement (3T, 50A): 1μm
Total displacement is weighted
sum of different modes
37. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
MODELING
ISMRM 2015 TORONTO, CANADA | 2015/06/05S. A. WINKLER
No displacement in
vertical direction
Hard acoustic
boundary
1
2
2
1. Structural vibration of coil
2. Acoustic wave propagation in
air
Infinite half space of air on both
bore ends
Perfectly
Matched
Layer
2
Insert gradient modeling: Surrounding air modeling:
Acousticwavepropagation:LorentzForces:
150
0
N/m
Fx
Fy
YX Z
820 Hz
Highly accurate prediction of SPL in gradient coils
acoustic-based design strategies for SPL reduction become possible
New features in gradient vibroacoustic modeling:
as compared to existing published modalities
-----------------------------------------------------------------------
1. Accurate wire patterns
2. Realistic bore shape with patient bridge
3. Acoustic propagation outside bore
4. Full coupling of vibrations and acoustics
5. Lorentz damping
39. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
Modes are shifted to
higher frequencies
and out of the band
of interest for RF
pulses
Extremely short axial
length of our head
gradient design
pushes
circumferential
modes to much
higher frequencies
These are not
excited by the z-
gradient short is
good!
S. A. WINKLER
(0,0,1)
(0,0,1)
(0,1,1)
(0,0,2)
(0,1,2)
(0,0,3)
(0,1,3) (1,0,2)
(coupled)
(0,5,4)
(0,0,2)
(0,1,5)
(1,0,3)
(2,0,3)
(1,0,3)
(2,0,3)
(2,2,1)
(3,0,3)
(4,0,0)
axial modes
radial modes
COMPARISON HEAD-BODY GRADIENTS
ETH ZÜRICH | 2014/12/19
41. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
EDDY CURRENT DAMPING
ISMRM 2015 TORONTO, CANADA | 2015/06/05S. A. WINKLER
Eddy current density induced in moving conductor
JCL = σ*(v x B0)
Lorentz force induced due to Eddy current
FCL = JCL*A x B0
Total force
F = FL + FCL
Total force explicit for B0 in z-direction:
F = FL - σAB0
2*v
Equation of motion
This damping term is
dependent on B0
2
nonlinear increase in SPLs
with field strength
42. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
NOISE REDUCTION METHODS
Moderate noise
reduction achieved
Current efforts for
sound reduction are
ongoing
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Bore acts as acoustic waveguide
Terminations to outside air are highly reflective bore
acts as resonator
1. impedance matching of waveguide to free space
impedance lets acoustic energy travel outward (horn)
2. absorbing endcap reduces resonances
Traveling wave concept using a horn.
Proposed noise reduction method
Winkler, Alejski, Wade, McKenzie, Rutt, ISMRM 2014
43. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
GRADIENT COIL ACOUSTICS – FIELD DEPENDENCE
Lorentz damping includedNo Lorentz damping
ISMRM 2015 TORONTO, CANADA | 2015/06/05S. A. WINKLER
7.5 dB from 3T to 7T
10.8 dB from 3T to 10.5 T
91.2 dB
97.5 dB
100.8 dB
3T:
7T:
10.5T:
92.1 dB
89.8 dB
90.5 dB
3T:
7T:
10.5T:
Linear scaling with main
field strength
Nonlinear scaling with
main field strength
44. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
GRADIENT COIL ACOUSTICS – FIELD DEPENDENCE
Lorentz damping includedNo Lorentz damping
ISMRM 2015 TORONTO, CANADA | 2015/06/05S. A. WINKLER
91.2 dB
97.5 dB
100.8 dB
3T:
7T:
10.5T:
92.1 dB
89.8 dB
90.5 dB
3T:
7T:
10.5T:
Coupled
resonanc
e
Linear scaling with main
field strength
Nonlinear scaling with
main field strength
46. STANFORD
UHF MRI
PROGRAM
B0SHIMMINGACOUSTICSSAFETYIMAGESHADINGINTRODUCTION
OTHER RESPONSIBILITIES AND THINGS I DO
Management of RF
and electronics lab
3D printer and
mechanical
manufacturing facility
management
ETH ZÜRICH | 2014/12/19S. A. WINKLER
Peripheral nerve
stimulation
Transcranial magnetic
stimulation
Molecular imaging –
magnetogenetics
Genetic activation for
cancer treatment by
alternating magnetic
field induced heating
…and many more!
47. THANK YOU!
ACKNOWLEDGEMENTS:
o ALL ANONYMOUS VOLUNTEERS
o MOHAMMAD MEHDI KHALIGHI
o KEVIN & KARLA EPPERSON
o IVES LEVESQUE
o THOMAS TOURDIAS
o ANNE SAWYER
o BRIAN HARGREAVES
o BRUCE DANIEL
o THOMAS WRIEDT
o JUERG FROEHLICH
o ZMT/SPEAG GMBH
COLLABORATORS:
o LARRY WALD
o JASON STOCKMANN
o BORIS KEIL
o MIHIR RAJENDRA PENDSE
o RICCARDO STARA
o ALESSANDRO SBRIZZI
o PAUL PICOT
o MICHAEL THORNTON
o TREVOR WADE
o ANDREW ALEJSKI
o CHARLES MCKENZIE
o JANOS BARTHA
ETH Zürich | 2014/12/19S. A. WINKLER
Editor's Notes
Maybe arrange the PIs in alphabetical order?
I edited the text on the right.
Technically, I suppose you could list Andrew, Janos, Trevor who are all on my payroll! But too late to get pictures and might confuse them at McGill.
I changed 40 to 50 – technically there are 54 7Ts (and 9 others above 7T), but not all of those have been installed at this time.
SNR varied with depth
Order we can achieve 3rd to 4th
5% center, 13% global, 15% cortex
Demanding test case EPI with a lot of distortion due to long echo train
No GRAPPA
GRAPPA: effective echo spacing goes down
It makes way more sense to plot the image value vs concentration – we’d see immediately the linearity and scatter, whereas with this table we don’t really appreciate anything intuitively.
I don’t see a huge value in showing the Hilbert Transform image. If reduces some of the bipolor or tripolar effects around the little tubes but introduces a lot of extraneous signal outside the tubes where there should be none, so it doesn’t seem to be demonstrating a net improvement compared to the unfilteredTA image.
I would use “will be” instead of “is” or “are” since you want to make it clear that this is speculation about a future implementation.
How many elements in these meshes?
--Approx. 120000, depends on coil. This is for faster simulation, may have slight inaccuracies at high frequency.
How long do simulations take?
--With this mesh a few hours. Also depends on coil.
What do the numbers (acceleration plots) mean? Have you double checked and confirmed numbers on Y gradient accelerations?
--Sorry I somehow sent you the old slide back. They are all average values across the 0-3000 Hz band.
Can you make the black experimental line (bottom plots) just a plain solid line, not with dots.
Can you use corresponding colors for both top and bottom: suggest black for simulation and red for experiment
--Done.
Not sure what you mean by “not excited by the Z-gradient” and whether the figure shows what you are trying to say here.
--Yes, this text is from when I showed the z-gradient. We don’t have a z-gradient pattern for the body coil so I can’t show that comparison. So this is simply an additional statement, in addition to the possible statement here that modes are shifted upwards in general.
You point out the frequency increase of some of the major modes in the body gradient, but not all of them. Is that because you can’t find correspondences in the head gradient for all of these?
--Kind of. This is tricky. I can’t really show all the modes, especially in the higher frequency range. Also they start to couple and you don’t easily understand what they are. I need to simulate the body gradient again because there are a few differences – that would be for the paper, and for tomorrow there isn’t enough time because this simulation would take a few days. The body gradient is really a beast. I prefer head gradients. :-)
Maybe you can use one color of arrow for one type of mode (eg circumferential) and another for another type?
--OK, I tried.
The head gradient overall SPL levels are down by a lot compared to body gradient until we get to some of the higher frequency modes and even there the baseline levels are still lower. Do we believe that result? Is there any experimental data to back this finding up?
--The Young’s modulus for the epoxy used in the body gradient coil is lower, i.e. less stiff. I don’t have time to re-run the simulation (body coil takes many days) and there are also some other things that are slightly different, but what should be visible is that the modes shift.