Development of limb volume measuring system

The mechanisms underlying the reductions in orthostatic tolerance associated with weightlessness are not well established. Contradictory results from measurements of leg volume changes suggest that altered venomotor tone and reduced blood flow may not be the only contributors to orthostatic intolerance. It is felt that a more accurate limb volume system which is insensitive to environmental factors will aid in better quantification of the hemodynamics of the leg. Of the varous limb volume techniques presently available, the ultrasonic limb volume system has proven to be the best choice. The system as described herein is free from environmental effects, safe, simple to operate and causes negligible radio frequency interference problems. The segmental ultrasonic ultrasonic plethysmograph is expected to provide a better measurement of limb volume change since it is based on cross-sectional area measurements

Power Approaches for Implantable Medical Devices.

Implantable medical devices have been implemented to provide treatment and to assess in vivo physiological information in humans as well as animal models for medical diagnosis and prognosis, therapeutic applications and biological science studies. The advances of micro/nanotechnology dovetailed with novel biomaterials have further enhanced biocompatibility, sensitivity, longevity and reliability in newly-emerged low-cost and compact devices. Close-loop systems with both sensing and treatment functions have also been developed to provide point-of-care and personalized medicine. Nevertheless, one of the remaining challenges is whether power can be supplied sufficiently and continuously for the operation of the entire system. This issue is becoming more and more critical to the increasing need of power for wireless communication in implanted devices towards the future healthcare infrastructure, namely mobile health (m-Health). In this review paper, methodologies to transfer and harvest energy in implantable medical devices are introduced and discussed to highlight the uses and significances of various potential power sources

SONAR SYSTEM SOFTWARE AND HARDWARE DEVELOPMENT: FISH FINDER APPLICATION

A study of how to develop a sonar system is presented in this thesis. A typical sonar system has two sub circuits, namely, transmit path and receive path. On transmit path, HV (high voltage) pulses are generated and transmitted into the water using a transducer. On the receive path, the echo of the transmitted signal is received. This received signal is then amplified and converted into digital data using an ADC. The digital data is then sent to a PC for signal processing. After signal processing, the results are shown in a GUI. Software technologies used in this study include Fish Finder GUI, Visual C++ GUI and back-end code, AFE5809 GUI, and High Speed Data Converter Pro (by Texas Instruments). Matlab was used to develop the Fish Finder GUI similar to commercial fish finders. The Fish Finder GUI also does noise filtering as well as calculating the depth and distance to the detected objects. Visual C++ was used to develop a software, called, Control GUI. This software, receives the data from the TSW1400, saves the data as a .CSV file. It also connects all used software programs together to work as a complete fish finder system. The developed sonar system was tested in 1-meter water, as well as 10-meter shore side test. First, HV pulse was generated and transmitted into the water. After that, the echo of the pulse was captured. Then, the echo was converted into digital data. Finally, the digital data was the digital data results were successfully shown in the GUIs.Chapter 1. Introduction 12 Chapter 2. Theory of Sonar Systems 15 2.1 Overview 15 2.2 Traditional pulse and Chirp 15 2.3 Sonar receive sub-path 16 2.4 Beamforming 17 2.5 Signal-to-Noise Ratio (SNR) 18 2.6 Velocity of sound in water 19 2.7 Sonar Transducer 20 Chapter 3. Sonar Prototype Hardware 21 3.1 Sonar System Prototype 21 3.2. Sonar Transmit Path Sub-Circuit 22 3.2.1 OMAP-L138: 22 3.2.2 HV (High-Voltage) Pulse Generator: 23 3.2.3 Transducer: 23 3.3. Sonar Receive Path Sub-Circuit 23 3.3.1 TX810 24 3.3.2 AFE5809 25 3.3.3 TSW1400 25 3.2.3 Transducer 25 3.3.4 PC 26 3.4. Details of each sonar component 26 3.4.1 OMAP-L138 26 3.4.2 OMAP-L138’s Enhanced High-Resolution Pulse-Width Modulator (eHRPWM) 27 3.4.3. HV (High-Voltage) Pulse Generator 29 3.4.4. Transducer 31 3.4.5. TX810: 32 3.4.6. AFE5809 33 3.4.7 TSW1400 36 Chapter 4. Sonar Prototype Software 39 4.1 SW.1 CCS: Control of A.1 OMAP-L138 39 4.2 SW.2 AFE5809 GUI: Control of B.2 AFE5809 40 4.3 SW.3 HSDC Pro: Control of B.3 TSW1400 41 4.4 SW.4 Control GUI: 42 4.5 SW.5 Fish Finder GUI: Signal Processing and GUI 43 Chapter 5. Experiments 47 5.1 Transmit Sub-Circuit Test 47 5.2 Receive Sub-Circuit Test 47 5.3 1-meter test 49 5.4 10-meter shore test 57 Chapter 6. Conclusion 60 Future direction 60 References 61 Appendix A. Control GUI 63 Appendix B. The Schematics of the custom HV Pulse Generator 73 Appendix C. Prototype Photos 74 Appendix D. Snippet of C++ code used to configure A.1 OMAP-L138’s eHRPWM 76 Appendix E. Snippet of the code behind Fish Finder GUI (Matlab) 78 Appendix F. Schematics of AFE5809 EVM 80 Appendix G. Schematic of TX810 EVM 90 Appendix H. Schematic of OMAP-L138 EVM 91Maste

Integrated Electronics for Wireless Imaging Microsystems with CMUT Arrays

Integration of transducer arrays with interface electronics in the form of single-chip CMUT-on-CMOS has emerged into the field of medical ultrasound imaging and is transforming this field. It has already been used in several commercial products such as handheld full-body imagers and it is being implemented by commercial and academic groups for Intravascular Ultrasound and Intracardiac Echocardiography. However, large attenuation of ultrasonic waves transmitted through the skull has prevented ultrasound imaging of the brain. This research is a prime step toward implantable wireless microsystems that use ultrasound to image the brain by bypassing the skull. These microsystems offer autonomous scanning (beam steering and focusing) of the brain and transferring data out of the brain for further processing and image reconstruction. The objective of the presented research is to develop building blocks of an integrated electronics architecture for CMUT based wireless ultrasound imaging systems while providing a fundamental study on interfacing CMUT arrays with their associated integrated electronics in terms of electrical power transfer and acoustic reflection which would potentially lead to more efficient and high-performance systems. A fully wireless architecture for ultrasound imaging is demonstrated for the first time. An on-chip programmable transmit (TX) beamformer enables phased array focusing and steering of ultrasound waves in the transmit mode while its on-chip bandpass noise shaping digitizer followed by an ultra-wideband (UWB) uplink transmitter minimizes the effect of path loss on the transmitted image data out of the brain. A single-chip application-specific integrated circuit (ASIC) is de- signed to realize the wireless architecture and interface with array elements, each of which includes a transceiver (TRX) front-end with a high-voltage (HV) pulser, a high-voltage T/R switch, and a low-noise amplifier (LNA). Novel design techniques are implemented in the system to enhance the performance of its building blocks. Apart from imaging capability, the implantable wireless microsystems can include a pressure sensing readout to measure intracranial pressure. To do so, a power-efficient readout for pressure sensing is presented. It uses pseudo-pseudo differential readout topology to cut down the static power consumption of the sensor for further power savings in wireless microsystems. In addition, the effect of matching and electrical termination on CMUT array elements is explored leading to new interface structures to improve bandwidth and sensitivity of CMUT arrays in different operation regions. Comprehensive analysis, modeling, and simulation methodologies are presented for further investigation.Ph.D

Contrast Enhanced Superharmonic Imaging for Acoustic Angiography Using Reduced Form-Factor Lateral Mode Transmitters for Intravascular and Intracavity Applications

Techniques to image the microvasculature may play an important role in imaging tumor-related angiogenesis and vasa vasorum associated with vulnerable atherosclerotic plaques. However, the microvasculature associated with these pathologies is difficult to detect using traditional B-mode ultrasound or even harmonic imaging due to small vessel size and poor differentiation from surrounding tissue. Acoustic angiography, a microvascular imaging technique which utilizes superharmonic imaging (detection of higher order harmonics of microbubble response), can yield a much higher contrast to tissue ratio (CTR) than second harmonic imaging methods. In this work, two dual-frequency transducers using lateral mode transmitters were developed for superharmonic detection and acoustic angiography imaging in intracavity applications. A single element dual-frequency IVUS transducer was developed for concept validation, which achieved larger signal amplitude, better contrast to noise ratio (CNR) and pulse length compared to the previous work. A dual-frequency PMN-PT array transducer was then developed for superharmonic imaging with dynamic focusing. The axial and lateral size of the microbubbles in a 200 μm tube were measured to be 269 μm and 200 μm, respectively. The maximum CNR was calculated to be 22 dB. These results show that superharmonic imaging with a low frequency lateral mode transmitter is a feasible alternative to thickness mode transmitters when final transducer size requirements dictate design choices

Pobudni sklop sa zaštitom od kvarnog stanja za pojačalo snage

This paper proposes a gate driver integrated circuit to prevent breakdown of switching power amplifiers. The proposed circuit consists of a dead-time generator, level shifters, and a breakdown blocker. The dead-time generator makes non-overlapped input signals and the breakdown blocker detects instantaneous turned-on input signals and resets them to the off-state before the switching power cells are damaged. The circuit is designed using TowerJazz\u27s 0.18 um BCD process for a tightly coupled wireless power transfer system. The protecting operation is verified using circuit simulation including layout-dependent characteristics.U ovom radu prikazan je pobudni sklop za sprječavanje kvarnog stanja pojačala snage. Predloženi krug sastoji se od generatora mrtvog vremena, translator razine i sklopa za sprječavanje kvarnog stanja. Generator mrtvog vremena tvori nepreklopljene ulazne signale, a sklop za sprječavanje kvarnog stanja prepoznaje trenutno paljenje ulaznog signala i resetira ih prije nego su ćelije pojačala snage oštećene. Krug je dizajniran koristeći TowerJazz\u27s 0.18 um BCD postupak za povezani sustav bežičnog prijenosa snage. Zaštita je verificirana koristeći simulaciju kruga uključujući karakteristike povezane s izgledom

Design and Implementation of a Low‐Power Wireless Respiration Monitoring Sensor

Wireless devices for monitoring of respiration activities can play a major role in advancing modern home-based health care applications. Existing methods for respiration monitoring require special algorithms and high precision filters to eliminate noise and other motion artifacts. These necessitate additional power consuming circuitry for further signal conditioning. This dissertation is particularly focused on a novel approach of respiration monitoring based on a PVDF-based pyroelectric transducer. Low-power, low-noise, and fully integrated charge amplifiers are designed to serve as the front-end amplifier of the sensor to efficiently convert the charge generated by the transducer into a proportional voltage signal. To transmit the respiration data wirelessly, a lowpower transmitter design is crucial. This energy constraint motivates the exploration of the design of a duty-cycled transmitter, where the radio is designed to be turned off most of the time and turned on only for a short duration of time. Due to its inherent duty-cycled nature, impulse radio ultra-wideband (IR-UWB) transmitter is an ideal candidate for the implementation of a duty-cycled radio. To achieve better energy efficiency and longer battery lifetime a low-power low-complexity OOK (on-off keying) based impulse radio ultra-wideband (IR-UWB) transmitter is designed and implemented using standard CMOS process. Initial simulation and test results exhibit a promising advancement towards the development of an energy-efficient wireless sensor for monitoring of respiration activities

High-Power Gallium Nitride HIFU Transmitter with Integrated Real-Time Current and Voltage Measurement

High-Intensity Focused Ultrasound (HIFU) therapy provides a non-invasive technique with which to destroy cancerous tissue without using ionizing radiation. To drive large single-element HIFU transducers, ultrasound transmitters capable of delivering high powers at relevant frequencies are required. The acoustic power delivered to a transducers focal region will determine the treated area, and due to safety concerns and intervening layers of attenuation, control of this output power is critical. A typical setup involves large inefficient linear power amplifiers to drive the transducer. Switched mode transmitters allow for a more compact drive system with higher efficiencies, with multi-level transmitters allowing control over the output power. Real-time monitoring of power delivered can avoid damage to the transducer and injury to patients due to over treatment, and allow for precise control over the output power. This study demonstrates a transformer-less, high power switched mode transmit transmitter based on Gallium-Nitride (GaN) transistors that is capable of delivering peak powers up to 1.8 kW at up to 600 Vpp, while operating at frequencies from DC to 5 MHz. The design includes a 12 bit 16 MHz floating Current/Voltage (I-V) measurement circuit to allow real-time high-side monitoring of the power delivered to the transducer allowing use with multi-element transducers

Applications of Wireless Power Transfer in Medicine : State-of-the-Art Reviews

Magnetic resonance within the field of wireless power transfer has seen an increase in popularity over the past decades. This rise can be attributed to the technological advances of electronics and the increased efficiency of popular battery technologies. The same principles of electromagnetic theory can be applied to the medical field. Several medical devices intended for use inside the body use batteries and electrical circuits that could be powered wirelessly. Other medical devices limit the mobility or make patients uncomfortable while in use. The fundamental theory of electromagnetics can improve the field by solving some of these problems. This survey paper summarizes the recent uses and discoveries of wireless power in the medical field. A comprehensive search for papers was conducted using engineering search engines and included papers from related conferences. During the initial search, 247 papers were found then non-relevant papers were eliminated to leave only suitable material. Seventeen relevant journal papers and/or conference papers were found, then separated into defined categories: Implants, Pumps, Ultrasound Imaging, and Gastrointestinal (GI) Endoscopy. The approach and methods for each paper were analyzed and compared yielding a comprehensive review of these state of the art technologies