Doppler catheter tip localization using color enhancement
Lee J. FrazinMichael J. VoneshAdel S. YaacoubBonnie J. KaneRodney GreeneW S KemperMichael GuberekDavid D. McPherson
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The objective of this research was to determine if the ultrasound emissions of the Doppler catheter can be used to locate its position in 3 dimensions by conventional echocardiography. A Doppler catheter has previously been shown to permit nonfluoroscopic retrograde catheterization of the aortic root and left ventricular chamber by using velocity waveform polarity for directional guidance. A significant difficulty in providing ultrasound catheter guidance, however, has been the inability to recognize the Doppler catheter tip, because each point at which a flexible catheter crosses the image plane can be misinterpreted as the catheter tip. Initial in vitro water bath trials were performed using the Doppler catheter attached to a standard velocimeter. Using a 5 MHz imaging transducer and color Doppler methods, the presence or absence of a banded color pattern which could demarcate the Doppler catheter tip was recorded at various angles in and out of the scanning plane. Using Doppler retrograde guidance and transesophageal echocardiography, color Doppler banded patterns, which could identify the Doppler catheter tip, were investigated in the dog aorta. In order to understand the physical mechanisms involved, a series of water bath trials were then conducted using the Doppler catheter attached to a velocimeter which was synchronized to the echo machine. Initial nonsynchronized water bath trials revealed distinct banded color patterns demarcating the Doppler catheter tip when it pointed in any direction within the beam width, except for a 40 degrees blind cone directly away from the imaging transducer.(ABSTRACT TRUNCATED AT 250 WORDS)A model array of 100 ADP crystal transducers designed to vibrate in a fundamental longitudinal mode was fabricated for the purpose of studying acoustic interactions in the NRL Acoustic Research Tank. To promote these interactions, the transducers were designed to have radiating faces of fractional wavelength size. Measurements were made on the full array as well as on smaller arrays. The objective of the study was to learn more about the parameters that affect the velocities or displacements of individual elements and thus the nearfield pressure patterns of multielement transducer arrays. Data obtained and presented in the form of curves, charts, and patterns indicate how the phase and amplitude of the displacements of transducer radiating faces is affected by parameters such as negative admittances, electrical drive conditions, and transducer element variations, location, and separation.
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Underwater Tonpilz transducer is designed with 1-3 piezocomposite materials to overcome the problems with conventional piezoceramic transducers. With the FEM, the variation of the resonance frequency, bandwidth and sound pressure of the transducer are analyzed in relation to the structural variables of the transducer. Through statistical multiple regression analysis of the results, functional forms of the transducer performance are derived in terms of design variables. By applying the constrained optimization technique, SQP-PD, to the derived functions, the optimal structure of the transducer is determined that can provide the highest sound pressure level at a given resonant frequency over a pre-determined frequency range. The validity of the optimized results is confirmed through comparison of the optimal performance with that of the FEA.
Optimal design
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An underwater Tonpilz transducer is designed with 1–3 piezocomposite materials to overcome the limitations of conventional piezoceramic transducers. With the finite element method (FEM), the variation of the resonance frequency, bandwidth and radiated sound pressure was analyzed in relation to the structural variables of the transducer. Through statistical multiple regression analysis of the finite element analysis (FEA) results, functional forms of the transducer performance are derived in terms of the design variables. Through the constrained minimization with the derived functions, the optimal structure of the transducer is determined to provide the highest sound pressure level at a given resonant frequency over a pre-determined frequency range. The validity of the optimization is confirmed by comparing the performance of the designed piezocomposite transducer with that of a conventional piezoceramic transducer.
Underwater Acoustics
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A new optical transducer for the detection of acoustic pressure in the diagnostic ultrasound frequency range is described. This transducer is based on the modulation of an evanescent light field by the incident acoustic energy. Theoretical design considerations are presented for the purpose of developing the most sensitive transducer. Based on these considerations an experimental transducer was constructed. Although less sensitive than predicted this device was capable of transducing ultrasonic pulses with a 1.0-MHz center frequency at diagnostic ultrasound amplitude levels. The techniques developed here are applicable for two-dimensional transduction and may prove a viable alternative to piezoelectric array transducers.
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The performance of a transducer is determined by the properties of constituent materials and the effects of many structural parameters. In this study, the use of 2-2 piezocomposite materials in an underwater Tonpilz transducer was investigated. Through finite element analyses, the relationship between the piezocomposite material properties and the performance of the transducer was investigated, i.e., operation frequency, bandwidth, and sound pressure. Based on the analysis result, the geometry of the Tonpilz transducer that could provide the highest sound pressure for a given electric field amplitude while satisfying requirements such as bandwidth and operation frequency was optimized. The optimization result was compared with that of a traditional piezoceramic transducer to confirm the superiority of the piezocomposite transducer; a Tonpilz transducer made of 2-2 mode piezocomposite plates could provide a higher effective coupling factor and thus a wider bandwidth at a desired operation frequency with a smaller size than a traditional piezoceramic transducer.
Underwater Acoustics
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The Tonpiltz transducer is one of the critical elements in sonar systems. The transducer's properties strongly depend on the number of piezoelectric ceramic segments and mechanical elements such as head mass, tail mass, prestress rod and so on. In this research, the relationship between the physical and electrical characteristics of the Tonpiltz transducer is deduced. The influences of material parameters and mechanical structure are also discussed. An ingenious method is proposed to evaluate the mechanical compliance and effective electromechanical coupling coefficient of the Tonpiltz transducer. A lumped equivalent circuit of the Tonpiltz transducer is also presented to estimate the weight and length of head and tail masses of the transducer, and to simulate the transducer's electrical and physical properties. A practical design example is also developed to confirm the simulation.
Smart transducer
Electromechanical coupling coefficient
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A wideband transducer for sound tube system is presented in this paper,which combines longitudinal transducer and ClassⅣflexural transducer to improve the performance at low frequency and broaden the working band.The equivalent electrical circuit is obtained by which the coupling between longitudinal transducer and flexural transducer is analyzed.A prototype is fabricated after analyzing the electro-acoustic performances by Finite Element Method.The standing wave in the sound tube stimulated by this transducer has been studied and the absorbing coefficients of two samples of acoustic materials are measured using this sound tube,which shows that the transducer can meet the requirements of measuring acoustic materials,especially with the wide working band ranging from 1.4 kHz to 23 kHz.
Wideband
Electromagnetic acoustic transducer
Smart transducer
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A wideband transducer for sound tube system is presented,which combines longitudinal transducer and ClassⅣflextensional transducer to improve the performance at low frequency and broaden the working band.The equivalent circuit is obtained and used to analyze the coupling mechanism between longitudinal transducer and flextensional transducer.A prototype of the transducer is developed after optimizing the electro-acoustic performances by Finite Element Method.The standing wave in the sound tube stimulated by this transducer has been studied and the sound absorbing coefficients of two acoustic materials samples are measured using this sound tube,which shows that the transducer can meet the requirements of acoustic material measurement with the working band ranging from 1.4 kHz to 23 kHz.
Wideband
Electromagnetic acoustic transducer
Smart transducer
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Piezoelectric underwater acoustic transducer is a kind of device for underwater detection working as not only an actuator but also a sensor.The technique of predicting acoustical characteristics of transducer is important to robust design of transducer in harsh underwater environment.Finite element methods are very powerful to characteristic analysis of transducers in different environments.Two dimensional axisymmetric finite element model of one type of Tonpilz transducer is generated and the dynamic analysis of it is conducted through a developing program based on finite element method.Some acoustic characteristics are obtained,and parts of them are compared with those from ANSYS.
Electromagnetic acoustic transducer
Underwater Acoustics
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