Yong Wang, T. Siginouchi, M. Hashimoto, H. Hachiya
Recently, we have proposed an ultrasonic multiple access method based on the spectrum spread technology using M-sequence codes. However, its effect depends on the preset threshold level. In this paper, we consider a novel quantitative estimation method using the normalized cross-correlation function between two microphones. Using this quantitative estimation method, we investigate the effect of the preset level and show the optimal value of the preset threshold.
{"title":"P2D-2 Quantitative Estimation of Ultrasonic Multiple Access Method Based on M-Sequence Code","authors":"Yong Wang, T. Siginouchi, M. Hashimoto, H. Hachiya","doi":"10.1109/ULTSYM.2007.396","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.396","url":null,"abstract":"Recently, we have proposed an ultrasonic multiple access method based on the spectrum spread technology using M-sequence codes. However, its effect depends on the preset threshold level. In this paper, we consider a novel quantitative estimation method using the normalized cross-correlation function between two microphones. Using this quantitative estimation method, we investigate the effect of the preset level and show the optimal value of the preset threshold.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"13 1","pages":"1575-1578"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86668832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ultrasound spatial compounding has been proven to successfully improve the image contrast, to achieve a more isotropic resolution and to reduce imaging artifacts in comparison with conventional B-mode imaging. For high- frequency ultrasound (HFUS) imaging of skin, usually linear scans only are performed perpendicularly to the axial direction of sound propagation. In this paper the potential of HFUS limited- angle spatial compounding for skin imaging is evaluated. We have implemented a new 20 MHz ultrasound system for limited- angle (up to plusmn40deg) spatial compound imaging. A sophisticated scanner was designed for high-resolution imaging with a spherically focused single-element transducer. The influence of unknown parameters of the system is eliminated by calibration measurements on a wire phantom. The imaging properties of the implemented system were assessed by means of phantom and in vivo measurements. A ray-tracing method for the compensation of artifacts, which are caused by refraction at the skin surface, is proposed and evaluated.
{"title":"4C-3 Limited-Angle Spatial Compound Imaging of Skin with High-Frequency Ultrasound (20 MHz)","authors":"M. Vogt, H. Ermert","doi":"10.1109/ULTSYM.2007.71","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.71","url":null,"abstract":"Ultrasound spatial compounding has been proven to successfully improve the image contrast, to achieve a more isotropic resolution and to reduce imaging artifacts in comparison with conventional B-mode imaging. For high- frequency ultrasound (HFUS) imaging of skin, usually linear scans only are performed perpendicularly to the axial direction of sound propagation. In this paper the potential of HFUS limited- angle spatial compounding for skin imaging is evaluated. We have implemented a new 20 MHz ultrasound system for limited- angle (up to plusmn40deg) spatial compound imaging. A sophisticated scanner was designed for high-resolution imaging with a spherically focused single-element transducer. The influence of unknown parameters of the system is eliminated by calibration measurements on a wire phantom. The imaging properties of the implemented system were assessed by means of phantom and in vivo measurements. A ray-tracing method for the compensation of artifacts, which are caused by refraction at the skin surface, is proposed and evaluated.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"41 3 1","pages":"240-243"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86955789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Introduction of a temporally periodic pressure field within a fluid can induce forced oscillations to bubbles present therein. The resultant [radial] bubble dynamics are a complex function of several parameters, including the driving pressure amplitude, and proximity to nearby boundaries, such as vessel walls, or indeed, other bubbles. Recently, experimentation gauged towards the development of a quantitative understanding of [acoustically] driven bubbles of micrometer dimensions, especially when close to boundaries, has become a challenge of heightened academic and industrial interest. In pursuit of this, the present authors pioneered a new approach to such measurements that exploits optical trapping to locate microbubbles at prescribed displacements from a boundary [1,2]. Here, we extend our previous method and report the first comprehensive study that has observed the dynamical behavior of isolated single micro-bubbles (the commercially available ultrasound contrast agent: SonoVue) that had been optically trapped over a range of well-defined displacements from a rigid boundary. All of the measurements were conducted at a mechanical index (MI) > 3. We noted a distinct variance in micro-bubble behavior across all quiescent radii and stand-off parameter, and also correlated bubble outcome statistics with measured radial dynamics. Finally, we suggest that the procedure outlined can be exploited to design ‘next-generation’ microbubbles with specific response characteristics.
{"title":"9B-2 Microbubble Interactions at High Mechanical Index: Ultrasound Stimulated Behaviour of SonoVue from Optically Predefined 'Stand-Off' Positions","authors":"J. M. Burns, P. Prentice, P. Campbell","doi":"10.1109/ULTSYM.2007.195","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.195","url":null,"abstract":"Introduction of a temporally periodic pressure field \u0000within a fluid can induce forced oscillations to bubbles present \u0000therein. The resultant [radial] bubble dynamics are a complex \u0000function of several parameters, including the driving pressure \u0000amplitude, and proximity to nearby boundaries, such as vessel \u0000walls, or indeed, other bubbles. Recently, experimentation \u0000gauged towards the development of a quantitative understanding \u0000of [acoustically] driven bubbles of micrometer dimensions, \u0000especially when close to boundaries, has become a challenge of \u0000heightened academic and industrial interest. In pursuit of this, \u0000the present authors pioneered a new approach to such \u0000measurements that exploits optical trapping to locate microbubbles \u0000at prescribed displacements from a boundary [1,2]. Here, \u0000we extend our previous method and report the first \u0000comprehensive study that has observed the dynamical behavior \u0000of isolated single micro-bubbles (the commercially available \u0000ultrasound contrast agent: SonoVue) that had been optically \u0000trapped over a range of well-defined displacements from a rigid \u0000boundary. All of the measurements were conducted at a \u0000mechanical index (MI) > 3. We noted a distinct variance in \u0000micro-bubble behavior across all quiescent radii and stand-off \u0000parameter, and also correlated bubble outcome statistics with \u0000measured radial dynamics. Finally, we suggest that the procedure \u0000outlined can be exploited to design ‘next-generation’ microbubbles \u0000with specific response characteristics.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"14 1","pages":"761-764"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88493608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hongyu Yu, Chuang-yuan Lee, W. Pang, Hao F. Zhang, E. S. Kim
This paper describes the oscillator based on high- overtone bulk acoustic resonator (HBAR) at 3.7 GHz for chip scale atomic clock (CSAC) application. The HBAR is built on a 400 mum thick sapphire with Al/ZnO/Al sandwich layers having thicknesses 0.1 mum/0.88 mum/0.1 mum, which ensures the best acoustic coupling and highest Q (above 19,000) at around 3.7 GHz. The oscillators have been designed, fabricated and measured to have very low phase noise and low power consumption. The oscillator when measured with agilent 4448 spectrum analyzer is measured to oscillate at 3.677 GHz with output signal power of -15 dBm and phase noise of -108 dBc/Hz at 10 kHz offset and -125 dBc/Hz @100 kHz offset, respectively, while consuming only 6.21 mW.
{"title":"12E-4 Low Phase Noise, Low Power Consuming 3.7 GHz Oscillator Based on High-Overtone Bulk Acoustic Resonator","authors":"Hongyu Yu, Chuang-yuan Lee, W. Pang, Hao F. Zhang, E. S. Kim","doi":"10.1109/ULTSYM.2007.293","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.293","url":null,"abstract":"This paper describes the oscillator based on high- overtone bulk acoustic resonator (HBAR) at 3.7 GHz for chip scale atomic clock (CSAC) application. The HBAR is built on a 400 mum thick sapphire with Al/ZnO/Al sandwich layers having thicknesses 0.1 mum/0.88 mum/0.1 mum, which ensures the best acoustic coupling and highest Q (above 19,000) at around 3.7 GHz. The oscillators have been designed, fabricated and measured to have very low phase noise and low power consumption. The oscillator when measured with agilent 4448 spectrum analyzer is measured to oscillate at 3.677 GHz with output signal power of -15 dBm and phase noise of -108 dBc/Hz at 10 kHz offset and -125 dBc/Hz @100 kHz offset, respectively, while consuming only 6.21 mW.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"10 1","pages":"1160-1163"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90669787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Lou-Meller, W. Wolny, E. Ringgaard, A. Nowicki, M. Lewandowski, W. Secomski
New types of thick-film transducers (19 to 37 MHz), with integrated highly attenuating ceramic backing formed of porous PZT material and shaped to the required ROC, were developed. For this project, focused transducers (focal depth 8.8 mm) with two different compositions, based on Ferroperm Pz24 (InSensor TF2400) and Pz26 (In Sensor TF2100), with different dielectric constant were fabricated. The transducers were carefully measured, then electrically and acoustically matched to the acoustical impedance of tissue and next mounted in a mechanical wobbling imaging probe. The transducers were excited with Golay coded sequences at 35 MHz. Introducing the coded excitation allowed replacing the short- burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The important factor for coded transmission/reception is the matching of the transducer bandwidth with the one of the coded signal. The thick films exhibited at least 30% bandwidth broadening comparing to the standard Pz27 transducer, resulting in an increase in matching filtering output by a factor of 1.4 - 1.5 and finally resulting in a SNR gain of the same order. Examples of skin scans obtained with the new thick-film transducers are presented. Further improvement of the transducer performance is demonstrated through optimizing the electrical impedance of the HF transducer. This is obtained by using a thick-film component prepared from a lower dielectric constant material, whilst the electromechanical coupling is maintained at approx. 50%.
{"title":"P5K-3 Novel Thick Film Transducers for High Frequency Ultrasonography","authors":"R. Lou-Meller, W. Wolny, E. Ringgaard, A. Nowicki, M. Lewandowski, W. Secomski","doi":"10.1109/ULTSYM.2007.603","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.603","url":null,"abstract":"New types of thick-film transducers (19 to 37 MHz), with integrated highly attenuating ceramic backing formed of porous PZT material and shaped to the required ROC, were developed. For this project, focused transducers (focal depth 8.8 mm) with two different compositions, based on Ferroperm Pz24 (InSensor TF2400) and Pz26 (In Sensor TF2100), with different dielectric constant were fabricated. The transducers were carefully measured, then electrically and acoustically matched to the acoustical impedance of tissue and next mounted in a mechanical wobbling imaging probe. The transducers were excited with Golay coded sequences at 35 MHz. Introducing the coded excitation allowed replacing the short- burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The important factor for coded transmission/reception is the matching of the transducer bandwidth with the one of the coded signal. The thick films exhibited at least 30% bandwidth broadening comparing to the standard Pz27 transducer, resulting in an increase in matching filtering output by a factor of 1.4 - 1.5 and finally resulting in a SNR gain of the same order. Examples of skin scans obtained with the new thick-film transducers are presented. Further improvement of the transducer performance is demonstrated through optimizing the electrical impedance of the HF transducer. This is obtained by using a thick-film component prepared from a lower dielectric constant material, whilst the electromechanical coupling is maintained at approx. 50%.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"65 1","pages":"2397-2400"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91084726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Capacitive micromachined ultrasound transducers (CMUTs) promise high transducer performance for several ultrasound applications. When making a focused ultrasound image with a 90 degree image sector we need a large number of individual elements. In off-axis beam steering neighbor elements operate at different phase. This leads to unwanted acoustic effects caused by the interaction with the fluid medium outside the array. We see high-Q resonances close to the center frequency of the array at off-axis angles, which we want to reduce. The present paper gives one approach to this. The introduction of a double periodicity, with a larger distance between elements than between CMUTs within an element is investigated. Simulations show that the resonances at frequencies closest to the center frequency are reduced, while they are increased at lower frequencies. The lowermost resonances are also shifted down in frequency by 1.5-2.5% of the center frequency. An added lossy top layer with thicknesses from 10 mum to 30 mum reduces the unwanted effects to an acceptable level, but increases the center frequency of the array. The combination of added element kerf and a lossy layer result in responses with 80-100% bandwidth and less than 1.5 dB insertion loss at 0 degrees steering angle. Reoptimizing the design might increase the bandwidth.
{"title":"P4M-9 Reduction of Crosstalk in CMUT Arrays by Introducing Double Periodicities","authors":"S. Berg, A. Rønnekleiv","doi":"10.1109/ULTSYM.2007.542","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.542","url":null,"abstract":"Capacitive micromachined ultrasound transducers (CMUTs) promise high transducer performance for several ultrasound applications. When making a focused ultrasound image with a 90 degree image sector we need a large number of individual elements. In off-axis beam steering neighbor elements operate at different phase. This leads to unwanted acoustic effects caused by the interaction with the fluid medium outside the array. We see high-Q resonances close to the center frequency of the array at off-axis angles, which we want to reduce. The present paper gives one approach to this. The introduction of a double periodicity, with a larger distance between elements than between CMUTs within an element is investigated. Simulations show that the resonances at frequencies closest to the center frequency are reduced, while they are increased at lower frequencies. The lowermost resonances are also shifted down in frequency by 1.5-2.5% of the center frequency. An added lossy top layer with thicknesses from 10 mum to 30 mum reduces the unwanted effects to an acceptable level, but increases the center frequency of the array. The combination of added element kerf and a lossy layer result in responses with 80-100% bandwidth and less than 1.5 dB insertion loss at 0 degrees steering angle. Reoptimizing the design might increase the bandwidth.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"24 1","pages":"2155-2158"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89486674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present an absolute transit time detection algorithm for ultrasonic gas flowmeters (UFMs). The major objective is a reliable and accurate detection, even when the received signals experience a change and degradation of their shape. This can be due to parasitic effects, such as high gas temperatures and pressure fluctuations. We employ a time and phase domain based detection algorithm that determines the absolute transit times independently for the upstream and downstream channel. The Hilbert transform is applied to calculate the wrapped phase signal; each section of this phase signal is analyzed step-by- step. The algorithm was tested on real measurement data obtained from a double-path UFM (wetted configuration using capacitive ultrasonic transducers) installed at the end of an exhaust gas train of an automotive combustion engine. Over a gas temperature range of 400degC and a mass flow range of 163 kg/h, corresponding to a signal- to-noise ratio (SNR) range from 18 to 8 dB, all transit times were detected correctly, i.e. without any cycle skip. Further, our results show that the algorithm outperforms cross-correlation methods in terms of the absolute transit time detection.
{"title":"3D-1 Absolute Transit Time Detection for Ultrasonic Gas Flowmeters Based on Time and Phase Domain Characteristics","authors":"M. Kupnik, E. Krasser, M. Groschl","doi":"10.1109/ULTSYM.2007.47","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.47","url":null,"abstract":"We present an absolute transit time detection algorithm for ultrasonic gas flowmeters (UFMs). The major objective is a reliable and accurate detection, even when the received signals experience a change and degradation of their shape. This can be due to parasitic effects, such as high gas temperatures and pressure fluctuations. We employ a time and phase domain based detection algorithm that determines the absolute transit times independently for the upstream and downstream channel. The Hilbert transform is applied to calculate the wrapped phase signal; each section of this phase signal is analyzed step-by- step. The algorithm was tested on real measurement data obtained from a double-path UFM (wetted configuration using capacitive ultrasonic transducers) installed at the end of an exhaust gas train of an automotive combustion engine. Over a gas temperature range of 400degC and a mass flow range of 163 kg/h, corresponding to a signal- to-noise ratio (SNR) range from 18 to 8 dB, all transit times were detected correctly, i.e. without any cycle skip. Further, our results show that the algorithm outperforms cross-correlation methods in terms of the absolute transit time detection.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"1 1","pages":"142-145"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89907359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to exploit complicated combinations of measurements associated with acoustic devices, we present the results of finite element/boundary element analyses including visco-elastic losses on fluid-loaded love-wave based devices, used as microbalance for biochemical detection and sensing purposes. The P-matrix characteristics of the mode are extracted from these computations to simulate the implemented devices. The corresponding frequency dependent phase shift and acoustic losses are introduced in the P-matrix model, allowing for an accurate prediction of insertion losses and phase sensitivity of our love-wave delay lines. Comparison between theory and experiments shows that we are capable to accurately predict the influence of viscosity on the insertion losses of the love-wave microbalance.
{"title":"6D-5 Modeling the Rf Acoustic Behavior of Love-Wave Sensors Loaded with Organic Layers","authors":"L. E. Fissi, J. Friedt, S. Ballandras","doi":"10.1109/ULTSYM.2007.130","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.130","url":null,"abstract":"In order to exploit complicated combinations of measurements associated with acoustic devices, we present the results of finite element/boundary element analyses including visco-elastic losses on fluid-loaded love-wave based devices, used as microbalance for biochemical detection and sensing purposes. The P-matrix characteristics of the mode are extracted from these computations to simulate the implemented devices. The corresponding frequency dependent phase shift and acoustic losses are introduced in the P-matrix model, allowing for an accurate prediction of insertion losses and phase sensitivity of our love-wave delay lines. Comparison between theory and experiments shows that we are capable to accurately predict the influence of viscosity on the insertion losses of the love-wave microbalance.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"97 1","pages":"484-487"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89985825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Foroughi, E. Boctor, M. Swartz, R. H. Taylor, G. Fichtinger
Segmentation of bone surface in ultrasound images has numerous applications in computer aided orthopedic surgery. A robust bone surface extraction technique for ultrasound images can be used to non-invasively probe the bone surface. In this work, we present early results with an intuitive and computationally inexpensive bone segmentation approach. The prior knowledge about the appearance of bone in ultrasound images is exploited toward achieving robust and fast bone segmentation. Continuity and smoothness of the bone surface are incorporated in a cost function, which is globally minimized using dynamic programming. The performance of this method is evaluated on ultrasound images collected from two male cadavers. The images are segmented in about half a second making the algorithm suitable for real-time applications. Comparison between manual and automatic segmentation shows an average accuracy of less than 3 pixels (0.3 mm).
{"title":"P6D-2 Ultrasound Bone Segmentation Using Dynamic Programming","authors":"P. Foroughi, E. Boctor, M. Swartz, R. H. Taylor, G. Fichtinger","doi":"10.1109/ULTSYM.2007.635","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.635","url":null,"abstract":"Segmentation of bone surface in ultrasound images has numerous applications in computer aided orthopedic surgery. A robust bone surface extraction technique for ultrasound images can be used to non-invasively probe the bone surface. In this work, we present early results with an intuitive and computationally inexpensive bone segmentation approach. The prior knowledge about the appearance of bone in ultrasound images is exploited toward achieving robust and fast bone segmentation. Continuity and smoothness of the bone surface are incorporated in a cost function, which is globally minimized using dynamic programming. The performance of this method is evaluated on ultrasound images collected from two male cadavers. The images are segmented in about half a second making the algorithm suitable for real-time applications. Comparison between manual and automatic segmentation shows an average accuracy of less than 3 pixels (0.3 mm).","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"36 1","pages":"2523-2526"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90794386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Laude, D. Gérard, N. Khelfaoui, C. Jerez-Hanckes, S. Benchabane, H. Moubchir, A. Khelif
Interdigital transducers (IDT) are widely used to generate surface acoustic waves directly on piezoelectric materials. However, in most applications, the generating fingers are straight, giving rise to the emission of plane waves. One notable exception is the circular IDT proposed by Day and Koerber for isotropic substrates [IEEE Trans. Sonics and Ultrason. SU-18, 461 (1972)]. More recently, the focused interdigital transducer (FIDT) has been used to obtain high intensity generation at the focal spot. The FIDT uses surface wave emission inside a circular arc for concentrating acoustic energy at its focus. However, the anisotropy of the substrate can lead to aberrations at the focal point. We investigate the problem of constructing an extended source that will focus elastic energy to a single point on the surface of a piezoelectric crystal. On the surface of a piezoelectric solid that is mechanically excited at a single point, concentric waves originate and form in the far field a ripple pattern that follows the shape of the wave surface, obtained by plotting the group velocity as a function of the emission angle. We conversely propose the concept of an annular interdigital transducer (AIDT), in which the shape of the fingers follows the wave surface. The surface acoustic waves generated by an AIDT are expected to converge to the center of the transducer, producing a spot that is limited in resolution by diffraction only. Experiments have been conducted on Y and Z cut lithium niobate (LiNbO3). AIDTs operating at a resonance frequency of 75 MHz have been constructed. Electrical measurements show that despite anisotropy in-phase emission at all angles is obtained for Rayleigh waves. In addition, spatial maps of the displacements at the surface have been obtained using a heterodyne optical probe, showing an important focusing of surface acoustic waves in the center of the device. The measured displacement fields at resonance show surface ripples converging to a spot at the center of the transducer. This result is promising for several applications including intense microacoustic sources.
{"title":"P4L-3 Anisotropic Wave-Surface Shaped Annular Interdigital Transducer","authors":"V. Laude, D. Gérard, N. Khelfaoui, C. Jerez-Hanckes, S. Benchabane, H. Moubchir, A. Khelif","doi":"10.1109/ULTSYM.2007.532","DOIUrl":"https://doi.org/10.1109/ULTSYM.2007.532","url":null,"abstract":"Interdigital transducers (IDT) are widely used to generate surface acoustic waves directly on piezoelectric materials. However, in most applications, the generating fingers are straight, giving rise to the emission of plane waves. One notable exception is the circular IDT proposed by Day and Koerber for isotropic substrates [IEEE Trans. Sonics and Ultrason. SU-18, 461 (1972)]. More recently, the focused interdigital transducer (FIDT) has been used to obtain high intensity generation at the focal spot. The FIDT uses surface wave emission inside a circular arc for concentrating acoustic energy at its focus. However, the anisotropy of the substrate can lead to aberrations at the focal point. We investigate the problem of constructing an extended source that will focus elastic energy to a single point on the surface of a piezoelectric crystal. On the surface of a piezoelectric solid that is mechanically excited at a single point, concentric waves originate and form in the far field a ripple pattern that follows the shape of the wave surface, obtained by plotting the group velocity as a function of the emission angle. We conversely propose the concept of an annular interdigital transducer (AIDT), in which the shape of the fingers follows the wave surface. The surface acoustic waves generated by an AIDT are expected to converge to the center of the transducer, producing a spot that is limited in resolution by diffraction only. Experiments have been conducted on Y and Z cut lithium niobate (LiNbO3). AIDTs operating at a resonance frequency of 75 MHz have been constructed. Electrical measurements show that despite anisotropy in-phase emission at all angles is obtained for Rayleigh waves. In addition, spatial maps of the displacements at the surface have been obtained using a heterodyne optical probe, showing an important focusing of surface acoustic waves in the center of the device. The measured displacement fields at resonance show surface ripples converging to a spot at the center of the transducer. This result is promising for several applications including intense microacoustic sources.","PeriodicalId":6355,"journal":{"name":"2007 IEEE Ultrasonics Symposium Proceedings","volume":"32 1","pages":"2115-2118"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89592384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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