Numerical Initial Value Problems in Ordinary Differential Equations

In an embodiment, a system includes one or one or more reservoirs responsive to control circuitry for receiving target(s) associated with one or more blood or lymph vessel of a subject. The system includes one or more first energy source associated with the one or more reservoirs for providing energy to elicit image response(s) associated with the target(s). The system includes one or more sensors associated with the one or more reservoirs for capturing the image response(s). Control circuitry is provided and coupled to the sensors for at least partially identifying the target(s) based at least partially on the captured image response(s) during an expected transit time of the target(s) through a detection area. Attachment unit(s) responsive to the control circuitry are provided for attaching the one or more reservoirs to the blood or lymph vessel.

Vasculature and lymphatic system imaging and ablation associated with a reservoir

This chapter contains sections titled: Historical Review Supervised Multilayer Networks Unsupervised Neural Networks: Kohonen Network Unsupervised Networks: Adaptive Resonance Theory Network Model Validation Summary References Recommended Exercises

Nonlinear System Identification

Capacitive micromachined ultrasonic transducers (CMUTs) have been subject to extensive research for the last two decades. Although they were initially developed for air-coupled applications, today their main application space is medical imaging and therapy. This paper first presents a brief description of CMUTs, their basic structure and operating principles. Our progression of developing several generations of fabrication processes is discussed with an emphasis on the advantages and disadvantages of each process. Monolithic and hybrid approaches for integrating CMUTs with supporting integrated circuits are surveyed. Several prototype transducer arrays with integrated front-end electronic circuits we developed and their use for 2D and 3D, anatomical and functional imaging, and ablative therapies are described. The presented results prove the CMUT as a micro-electro-mechanical systems technology for many medical diagnostic and therapeutic applications.

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Capacitive micromachined ultrasonic transducers for medical imaging and therapy

This page shows some examples of multimedia files. It is also available at: http://www.ieee-uffc.org/tr/mexample.pdf. For submission of multimedia manuscripts to TUFFC, please follow “Information for Contributors” at: http://www.ieeeuffc.org/tr/contrib.pdf. Multimedia Example Created by Jian-yu Lu, Editor-in-Chief, 07/07/03 IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society 1. Color Figure: The IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (TUFFC) now accepts color figures online with corresponding grayscale figures in print without additional charges if authors follow the multimedia manuscript submission procedure in the “Information for Contributors”. The “color figures” icon below indicates in the print that a color version of the figure is available online. It also links to the color figure submitted originally by the authors for viewing details. Because of the sizes of color figures and the additional editorial work such as making two sets of PostScript files in which they remain identical after replacing grayscale with color, authors should request color figures online only when it is necessary. The color figure must be in JPEG (Joint Photographic Expert Group) or GIF (Graphics Interchange Format) format to reduce file size and to decrease the bandwidth usage on the TUFFC server. Fig. 1. An eight-layer printed circuit board (PCB) used primarily for multi-channel ultrasound signal reception and storage. The board was designed in the Ultrasound Lab at The University of Toledo, led by Dr. Jian-yu Lu. It is one of the many PCBs designed for a high-frame rate medical ultrasound imaging system [1], which consists of 128 linear, ±144V peak, 0.05-10MHz, and 12-bit arbitrary waveform generators for the production of ultrasound signals or for other research purposes. 2. Movies: Please click on the movie icon to see a movie. The two movies below give you an idea on the file size versus movie quality. “VCD quality” here means 1150kbits/s for video and 224kbits/s for 16-bit MP2 stereo audio at 44.1KHz sampling rate. Fig. 2. An introduction to the Ultrasound Lab at The University of Toledo. 3. Movies and Animations: Please click on the movie icons to see movies or animations. Fig. 3. Circuit design and construction of the imaging system. 4. Movies and Animation: Please click on the movie icons to see movies or animation. Movie [File size: 785KB; Format: MPEG1; Resolution: 320X240; Duration: 9 seconds]

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control

For three-dimensional (3D) ultrasound imaging, connecting elements of a two-dimensional (2D) transducer array to the imaging system's front-end electronics is a challenge because of the large number of array elements and the small element size. To compactly connect the transducer array with electronics, we flip-chip bond a 2D 16 times 16-element capacitive micromachined ultrasonic transducer (CMUT) array to a custom-designed integrated circuit (IC). Through-wafer interconnects are used to connect the CMUT elements on the top side of the array with flip-chip bond pads on the back side. The IC provides a 25-V pulser and a transimpedance preamplifier to each element of the array. For each of three characterized devices, the element yield is excellent (99 to 100% of the elements are functional). Center frequencies range from 2.6 MHz to 5.1 MHz. For pulse-echo operation, the average -6-dB fractional bandwidth is as high as 125%. Transmit pressures normalized to the face of the transducer are as high as 339 kPa and input-referred receiver noise is typically 1.2 to 2.1 rnPa/ radicHz. The flip-chip bonded devices were used to acquire 3D synthetic aperture images of a wire-target phantom. Combining the transducer array and IC, as shown in this paper, allows for better utilization of large arrays, improves receive sensitivity, and may lead to new imaging techniques that depend on transducer arrays that are closely coupled to IC electronics.

Integration of 2D CMUT arrays with front-end electronics for volumetric ultrasound imaging

Forward-viewing ring arrays can enable new applications in intravascular and intracardiac ultrasound. This work presents compelling, full-synthetic, phased-array volumetric images from a forward-viewing capacitive micromachined ultrasonic transducer (CMUT) ring array wire bonded to a custom integrated circuit front end. The CMUT ring array has a diameter of 2 mm and 64 elements each 100 /spl mu/m /spl times/ 100 /spl mu/m in size. In conventional mode, echo signals received from a plane reflector at 5 mm had 70% fractional bandwidth around a center frequency of 8.3 MHz. In collapse mode, 69% fractional bandwidth is measured around 19 MHz. Measured signal-to-noise ratio (SNR) of the echo averaged 16 times was 29 dB for conventional operation and 35 dB for collapse mode. B-scans were generated of a target consisting of steel wires 0.3 mm in diameter to determine resolution performance. The 6 dB axial and lateral resolutions for the B-scan of the wire target are 189 /spl mu/m and 0.112 radians for 8 MHz, and 78 /spl mu/m and 0.051 radians for 19 MHz. A reduced firing set suitable for real-time, intravascular applications was generated and shown to produce acceptable images. Rendered three-dimensional (3-D) images of a Palmaz-Schatz stent also are shown, demonstrating that the imaging quality is sufficient for practical applications.

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3-D ultrasound imaging using a forward-looking CMUT ring array for intravascular/intracardiac applications

This paper reports on the experimental characterization of collapse-mode operation of capacitive micromachined ultrasonic transducers (CMUTs). CMUTs are conventionally operated by applying a direct current (DC) bias voltage less than the collapse voltage of the membrane, so that the membrane is deflected toward the bottom electrode. In the conventional regime, there is no contact between the membrane and the substrate; the maximum alternating current (AC) displacement occurs at the center of the membrane. In collapse-mode operation, the DC bias voltage is first increased beyond the collapse voltage, then reduced without releasing the collapsed membrane. In collapse-mode operation, the center of the membrane is always in contact with the substrate. In the case of a circular membrane, the maximum AC displacement occurs along the ring formed between the center and the edge of the membrane. The experimental characterization presented in this paper includes impedance measurements in air, pulse-echo experiments in immersion, and one-way optical displacement measurements in immersion for both conventional and collapse-mode operations. A 205-mum times 205-mum 2-D CMUT array element composed of circular silicon nitride membranes is used in the experiments. In pulse-echo experiments, a custom integrated circuit (IC) comprising a pulse driver, a transmit/receive switch, a wideband low-noise preamplifier, and a line driver is used. By reducing the parasitic capacitance, the use of a custom IC enables pulse-echo measurements at high frequencies with a very small transducer. By comparing frequency response and efficiency of the transducer in conventional and collapse regimes, experimental results show that a collapsed membrane can be used to generate and detect ultrasound more efficiently than a membrane operated in the conventional mode. Furthermore, the center frequency of the collapsed membrane can be changed by varying the applied DC voltage. In this study, the center frequency of a collapsed transducer in immersion is shown to vary from 20 MHz to 28 MHz with applied DC bias; the same transducer operates at 10 MHz in the conventional mode. In conventional mode, the maximum peak-to-peak pressure is 370 kPa on the transducer surface for a 40-ns, 25-V unipolar pulse excitation. In collapse mode, a 25-ns, 25-V unipolar pulse generates 590 kPa pressure at the surface of the transducer

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Experimental characterization of collapse-mode CMUT operation

Although semiconductor technologies have displaced vacuum-tube devices in nearly all fields of electronics, vacuum tubes are still widely used in professional guitar amplifiers. A major reason for this is that electric-guitar amplifiers are typically overdriven, that is, operated in such a way that the output saturates. Vacuum tubes distort the signal in a different manner compared to solid-state electronics, and human listeners tend to prefer this. This might be because the distinctive tone of tube amplifiers was popularized in the 1950s and 1960s by early rock and roll bands, so musicians and listeners have become accustomed to tube distortion. Some studies on the perceptual aspects of vacuum-tube and solid-state distortion have been published (e.g., Hamm 1973; Bussey and Haigler 1981; Santo 1994). Despite their acclaimed tone, vacuum-tube amplifiers have certain shortcomings: large size and weight, poor durability, high power consumption, high price, and often poor availability of spare parts. Thus, it is not surprising that many attempts have been made to emulate guitar tube amplifiers using smaller and cheaper solid-state analog circuits (e.g., Todokoro 1976; Sondermeyer 1984). The next step in the evolution of tube-amplifier emulation has been to simulate the amplifiers using computers and digital signal processors (DSP). A primary advantage of digital emulation is that the same hardware can be used for modeling many different tube amplifiers and effects. When a new model is to be added, new parameter values or program code are simply uploaded to the device. Furthermore, amplifier models can be implemented

A review of digital techniques for modeling vacuum-tube guitar amplifiers

This paper presents a procedural approach to derive nonlinear filters from schematics of audio circuits for the purpose of digitally emulating analog musical effects circuits in real time. This work, the first in a two-part series, extends a well-known efficient nonlinear continuous-time state-space formulation for physical modeling of musical acoustics to real-time modeling of nonlinear circuits. Rules for applying the formulation are given, as well as a procedure to derive simulation parameters automatically from circuit netlists. Furthermore, a related nonlinear discrete-time state-space algorithm is proposed to alleviate problems in solving particular circuit configurations. These methods were devised to solve non-convergence problems in the simulation of strongly saturated, nonparametric guitar distortion circuits such as the saturating diode clipper, which is presented as an example derivation. Experimental considerations and sonic performance on various other circuits will be presented in a subsequent paper.

David T. Yeh

Papers

Integration of 2D CMUT arrays with front-end electronics for volumetric ultrasound imaging

3-D ultrasound imaging using a forward-looking CMUT ring array for intravascular/intracardiac applications

Experimental characterization of collapse-mode CMUT operation

A review of digital techniques for modeling vacuum-tube guitar amplifiers

Automated Physical Modeling of Nonlinear Audio Circuits For Real-Time Audio Effects—Part I: Theoretical Development