Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921653
X. Hao, Charles J Bruce, C. Pislaru, James F. Greenleaf
Region growing is performed in a multi-feature vector space. Three novel criteria are developed for region growing control. First, instead of using the local information as do the conventional region growing methods, this method uses global information. Second, to overcome the effects of speckle noise and attenuation artifacts, a new idea termed, "geographic similarity", is introduced. Third, an equal opportunity competence criterion is employed to make results independent of processing order. Segmentation results for in vivo intracardiac ultrasound images and the corresponding statistical analyses show that this method is reliable and effective.
{"title":"A novel region growing method for segmenting ultrasound images","authors":"X. Hao, Charles J Bruce, C. Pislaru, James F. Greenleaf","doi":"10.1109/ULTSYM.2000.921653","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921653","url":null,"abstract":"Region growing is performed in a multi-feature vector space. Three novel criteria are developed for region growing control. First, instead of using the local information as do the conventional region growing methods, this method uses global information. Second, to overcome the effects of speckle noise and attenuation artifacts, a new idea termed, \"geographic similarity\", is introduced. Third, an equal opportunity competence criterion is employed to make results independent of processing order. Segmentation results for in vivo intracardiac ultrasound images and the corresponding statistical analyses show that this method is reliable and effective.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132455931","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921560
J. Zachary, L. Frizzell, W. O’Brien
Ultrasound has an exceptional safety record, but concerns have been raised by reports of clinical-level ultrasound-induced lung haemorrhage in mice, rats, rabbits, monkeys, and pigs. This study characterized the temporal reparative (healing) responses in lung following the induction of lesions by pulsed ultrasound (3.14 MHz, 1700-Hz PRF, 1.4-/spl mu/s pulse duration, 60-s exposure duration, in situ [at the pleural surface] peak rarefactional pressure of 17 MPa, and in situ peak compressional pressure of 39.7 MPa). Following exposure, lung lesions were evaluated at 0, 1, 2, 5, 7, 9, 12, 14, and 16 days post exposure (dpe). Lungs were scored for the presence of lesions, recorded digitally, and fixed in 10% formalin. After fixation, the dimensions of each lesion at the visceral pleural surface were measured. The lesions were bisected and the depth measured. The temporal changes were indicative of degradation of erythrocytes through processing and removal of hemoglobin and iron pigments. Microscopic lesions paralleled the gross lesions and reparative responses resulted in minimal alteration of lung structure. The reparative response in lung was analogous to reparative responses in soft tissues associated with bruising, but also had a proliferative phase characterized by focal hyperplasia of spindloid cells whose phenotypes need to be determined.
{"title":"Lesion resolution following exposure of rat lung to pulsed ultrasound","authors":"J. Zachary, L. Frizzell, W. O’Brien","doi":"10.1109/ULTSYM.2000.921560","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921560","url":null,"abstract":"Ultrasound has an exceptional safety record, but concerns have been raised by reports of clinical-level ultrasound-induced lung haemorrhage in mice, rats, rabbits, monkeys, and pigs. This study characterized the temporal reparative (healing) responses in lung following the induction of lesions by pulsed ultrasound (3.14 MHz, 1700-Hz PRF, 1.4-/spl mu/s pulse duration, 60-s exposure duration, in situ [at the pleural surface] peak rarefactional pressure of 17 MPa, and in situ peak compressional pressure of 39.7 MPa). Following exposure, lung lesions were evaluated at 0, 1, 2, 5, 7, 9, 12, 14, and 16 days post exposure (dpe). Lungs were scored for the presence of lesions, recorded digitally, and fixed in 10% formalin. After fixation, the dimensions of each lesion at the visceral pleural surface were measured. The lesions were bisected and the depth measured. The temporal changes were indicative of degradation of erythrocytes through processing and removal of hemoglobin and iron pigments. Microscopic lesions paralleled the gross lesions and reparative responses resulted in minimal alteration of lung structure. The reparative response in lung was analogous to reparative responses in soft tissues associated with bruising, but also had a proliferative phase characterized by focal hyperplasia of spindloid cells whose phenotypes need to be determined.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122180491","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.922564
N. Emanetoglu, G. Patounakis, S. Muthukumar, Y. Lu
Temperature stable SAW filters are needed in many communication and sensor applications. The ZnO/SiO/sub 2//Si structure is particularly attractive, as ZnO and Si have positive TCD whereas SiO/sub 2/ has negative TCD, from which temperature compensation may be achieved. Furthermore, it allows integration of surface acoustic wave devices with Si circuits for compact communications and sensor systems. In this work, temperature compensated SAW modes in the ZnO/SiO/sub 2//Si structure have been investigated through computer simulation using the transfer matrix method. Through proper design of the layer thickness', second order and higher wave modes with temperature compensation at multiple frequency points in the 1 GHz to 2.5 GHz range are achieved. Based on the simulation results on the thickness' of SiO/sub 2/ and ZnO layers, ZnO thin films were grown on SiO/sub 2//Si substrates using the MOCVD technique. Measurement results from SAW test devices are compared with the temperature compensated wave modes predicted by the simulations.
{"title":"Analysis of temperature compensated SAW modes in ZnO/SiO/sub 2//Si multilayer structures","authors":"N. Emanetoglu, G. Patounakis, S. Muthukumar, Y. Lu","doi":"10.1109/ULTSYM.2000.922564","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.922564","url":null,"abstract":"Temperature stable SAW filters are needed in many communication and sensor applications. The ZnO/SiO/sub 2//Si structure is particularly attractive, as ZnO and Si have positive TCD whereas SiO/sub 2/ has negative TCD, from which temperature compensation may be achieved. Furthermore, it allows integration of surface acoustic wave devices with Si circuits for compact communications and sensor systems. In this work, temperature compensated SAW modes in the ZnO/SiO/sub 2//Si structure have been investigated through computer simulation using the transfer matrix method. Through proper design of the layer thickness', second order and higher wave modes with temperature compensation at multiple frequency points in the 1 GHz to 2.5 GHz range are achieved. Based on the simulation results on the thickness' of SiO/sub 2/ and ZnO layers, ZnO thin films were grown on SiO/sub 2//Si substrates using the MOCVD technique. Measurement results from SAW test devices are compared with the temperature compensated wave modes predicted by the simulations.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133323531","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921488
K.L. Gentry, J. Zara, S. Bu, C. Eom, S.W. Smith
A sol gel process has been used to develop a 30 /spl mu/m thick PZT coating on a sapphire wafer. The sol gel film was removed and plated with platinum electrodes. The free-standing film had a free dielectric constant (/spl epsiv//sup T/) of 820, a thickness-mode coupling coefficient (k/sub t/) of 0.17, a speed of sound (c) of 3700 m/s, and an acoustic impedance (Z) of 28.9 MRayls. The film resonated at 62 MHz. These results were similar to KLM simulation results. A sol gel transducer was built by first backing the film with 2.2 mm thick silver epoxy. The transducer resonated at 32, 64, and 92 MHz. At 32 MHz, the transducer had a bandwidth of 40%. The insertion loss at 47 MHz was -66 dB. A 32 MHz image was constructed with this transducer by off-line processing of 40 rf-lines of data.
{"title":"Thick film sol gel PZT transducer using dip coating","authors":"K.L. Gentry, J. Zara, S. Bu, C. Eom, S.W. Smith","doi":"10.1109/ULTSYM.2000.921488","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921488","url":null,"abstract":"A sol gel process has been used to develop a 30 /spl mu/m thick PZT coating on a sapphire wafer. The sol gel film was removed and plated with platinum electrodes. The free-standing film had a free dielectric constant (/spl epsiv//sup T/) of 820, a thickness-mode coupling coefficient (k/sub t/) of 0.17, a speed of sound (c) of 3700 m/s, and an acoustic impedance (Z) of 28.9 MRayls. The film resonated at 62 MHz. These results were similar to KLM simulation results. A sol gel transducer was built by first backing the film with 2.2 mm thick silver epoxy. The transducer resonated at 32, 64, and 92 MHz. At 32 MHz, the transducer had a bandwidth of 40%. The insertion loss at 47 MHz was -66 dB. A 32 MHz image was constructed with this transducer by off-line processing of 40 rf-lines of data.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124868280","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921604
Yi Zheng, Aiping Yao, J. Greenleaf
A trapezoid filter is introduced to map Doppler signals to spectral lines that associate to different velocities of scatterers. The filter completely rejects frequencies outside of a trapezoid area in the two-dimensional Fourier domain of Doppler RF signals. A three-dimensional Doppler image (or a movie of a two-dimensional image) with dimensions of location, Doppler spectrum, and time, can be obtained by listing the spectral lines along the beam axis. Gated integration of the Doppler image produces a coded map showing moving scatterers with different velocities. Experiments were performed using a peripheral vascular Doppler flow phantom. The method successfully differentiated the scatterers with different velocities at 29.8 cm/s and 14.6 cm/s. This new approach has potential for characterizing moving scatterers having different velocities within a sample volume.
{"title":"Differentiation of moving scatterers with different velocities using trapezoid filter and pulse echo ultrasound","authors":"Yi Zheng, Aiping Yao, J. Greenleaf","doi":"10.1109/ULTSYM.2000.921604","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921604","url":null,"abstract":"A trapezoid filter is introduced to map Doppler signals to spectral lines that associate to different velocities of scatterers. The filter completely rejects frequencies outside of a trapezoid area in the two-dimensional Fourier domain of Doppler RF signals. A three-dimensional Doppler image (or a movie of a two-dimensional image) with dimensions of location, Doppler spectrum, and time, can be obtained by listing the spectral lines along the beam axis. Gated integration of the Doppler image produces a coded map showing moving scatterers with different velocities. Experiments were performed using a peripheral vascular Doppler flow phantom. The method successfully differentiated the scatterers with different velocities at 29.8 cm/s and 14.6 cm/s. This new approach has potential for characterizing moving scatterers having different velocities within a sample volume.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117041516","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921635
J. Aubry, J. Gerber, M. Tanter, J. Thomas, M. Fink
Ultrasonic imaging system capabilities are strongly dependent on the focusing quality of the ultrasonic beam. The beam width and sidelobe level constrain respectively the resolution and contrast of the final image. In the case of brain imaging, it is well-known that the skull strongly degrades the ultrasonic focusing pattern by introducing substantial phase and amplitude aberrations of the wavefront. In previous work, this degradation of the beam focus had been partially corrected by coupling the time reversal focusing process to an amplitude compensation of the emitted signals. In that case, the optimal focus was reproduced down to -20 dB, but the sidelobe level remained at about -25 dB. We propose here a new focusing technique based on the calculation of the spatio-temporal inverse filter of the propagation. Experimental focusing through the skull is now comparable to the focusing in a homogeneous medium. In the transmit-receive mode, focusing through the skull could reach the optimal level obtained in water down to -70 dB (i.e. constrained only by experimental noise levels.).
{"title":"Towards ultrasonic brain imaging","authors":"J. Aubry, J. Gerber, M. Tanter, J. Thomas, M. Fink","doi":"10.1109/ULTSYM.2000.921635","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921635","url":null,"abstract":"Ultrasonic imaging system capabilities are strongly dependent on the focusing quality of the ultrasonic beam. The beam width and sidelobe level constrain respectively the resolution and contrast of the final image. In the case of brain imaging, it is well-known that the skull strongly degrades the ultrasonic focusing pattern by introducing substantial phase and amplitude aberrations of the wavefront. In previous work, this degradation of the beam focus had been partially corrected by coupling the time reversal focusing process to an amplitude compensation of the emitted signals. In that case, the optimal focus was reproduced down to -20 dB, but the sidelobe level remained at about -25 dB. We propose here a new focusing technique based on the calculation of the spatio-temporal inverse filter of the propagation. Experimental focusing through the skull is now comparable to the focusing in a homogeneous medium. In the transmit-receive mode, focusing through the skull could reach the optimal level obtained in water down to -70 dB (i.e. constrained only by experimental noise levels.).","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129506903","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921575
J. Jenne, M. Moosmann, I. Simiantonakis, R. Rastert, P. Huber, M. Rheinwald, T. Haase, J. Debus
High intensity ultrasound fields have the potential to produce free radicals in aqueous solutions caused by inertial cavitation. In this study we compared the production of free radicals under different sonication modalities with radical formation in the field of a well known Cs/sup 137/ gamma-ray source. In addition we examined the enhancement of radical production by photodynamic substances. Analysis of radical formation was performed with an ESR spectrometer. Sonication of aqueous test solution was carried out with high intensity focused ultrasound (HIFU) and with an unfocused ultrasound field in a standing wave mode against a solution/air interface. We were able to assess the quantity of free radicals developing in photon field as well as in US fields. It was feasible to determine equivalent dose values comparing ultrasound with photon irradiation. A significant enhancement of radical production by a photosensitizer was only detected in the unfocused ultrasound field in a standing wave mode.
{"title":"ESR dosimetry of free radicals-a comparison between high intensity ultrasound fields and an ionizing Cs/sup 137/ source","authors":"J. Jenne, M. Moosmann, I. Simiantonakis, R. Rastert, P. Huber, M. Rheinwald, T. Haase, J. Debus","doi":"10.1109/ULTSYM.2000.921575","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921575","url":null,"abstract":"High intensity ultrasound fields have the potential to produce free radicals in aqueous solutions caused by inertial cavitation. In this study we compared the production of free radicals under different sonication modalities with radical formation in the field of a well known Cs/sup 137/ gamma-ray source. In addition we examined the enhancement of radical production by photodynamic substances. Analysis of radical formation was performed with an ESR spectrometer. Sonication of aqueous test solution was carried out with high intensity focused ultrasound (HIFU) and with an unfocused ultrasound field in a standing wave mode against a solution/air interface. We were able to assess the quantity of free radicals developing in photon field as well as in US fields. It was feasible to determine equivalent dose values comparing ultrasound with photon irradiation. A significant enhancement of radical production by a photosensitizer was only detected in the unfocused ultrasound field in a standing wave mode.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129803540","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921559
W. O’Brien, L. Frizzell, D. Schaeffer, J. Zachary
Superthreshold behavior for ultrasound-induced lung haemorrhage was investigated in 150 mice and 150 rats at 2.8 MHz to assess the role of pulse repetition frequency (PRF) and exposure duration (ED). Each species was divided into 15 exposure groups (10 per group) for a 3/spl times/5 randomized factorial design (3 EDs of 5, 10 and 20 s; and 5 PRFs of 25, 50, 100, 250 and 500 Hz). The in situ peak rarefactional pressure (12.3 MPa) and pulse duration (1.42 /spl mu/s) were the same for all ultrasonically exposed animals. Also, for both species, 15 sham-exposed animals were randomized into both studies, none of which had lesions. Factorial analysis of variance was used to evaluate effects of PRF and ED on the proportion of lesions, lesion depth and lesion surface area. The proportion of lesions in both species was related statistically to PRF and ED, with the exception that PRF in rats was not quite significant. The PRF, but not ED, significantly affected lesion depth in both species. Both PRF and ED significantly affected lesion surface area in mice, while neither affected area in rats. The PRF/spl times/ED interaction (number of pulses) for these measures was not significant for either species. Species significantly affected lesion production and size; there were fewer lesions in mice, and the lesion size was greater in rats. The characteristics of the lesions produced in both species were similar to those described in studies by our research group and others, suggesting a common pathogenesis for the initiation and propagation of the lesions at the gross and microscopic levels.
{"title":"Role of pulse repetition frequency and exposure duration on the superthreshold behavior of ultrasound-induced lung haemorrhage in adult mice and rats","authors":"W. O’Brien, L. Frizzell, D. Schaeffer, J. Zachary","doi":"10.1109/ULTSYM.2000.921559","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921559","url":null,"abstract":"Superthreshold behavior for ultrasound-induced lung haemorrhage was investigated in 150 mice and 150 rats at 2.8 MHz to assess the role of pulse repetition frequency (PRF) and exposure duration (ED). Each species was divided into 15 exposure groups (10 per group) for a 3/spl times/5 randomized factorial design (3 EDs of 5, 10 and 20 s; and 5 PRFs of 25, 50, 100, 250 and 500 Hz). The in situ peak rarefactional pressure (12.3 MPa) and pulse duration (1.42 /spl mu/s) were the same for all ultrasonically exposed animals. Also, for both species, 15 sham-exposed animals were randomized into both studies, none of which had lesions. Factorial analysis of variance was used to evaluate effects of PRF and ED on the proportion of lesions, lesion depth and lesion surface area. The proportion of lesions in both species was related statistically to PRF and ED, with the exception that PRF in rats was not quite significant. The PRF, but not ED, significantly affected lesion depth in both species. Both PRF and ED significantly affected lesion surface area in mice, while neither affected area in rats. The PRF/spl times/ED interaction (number of pulses) for these measures was not significant for either species. Species significantly affected lesion production and size; there were fewer lesions in mice, and the lesion size was greater in rats. The characteristics of the lesions produced in both species were similar to those described in studies by our research group and others, suggesting a common pathogenesis for the initiation and propagation of the lesions at the gross and microscopic levels.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"211 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123267709","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}
Pub Date : 2000-12-01DOI: 10.1109/ULTSYM.2000.921671
T. Oliphant, R. Kinnick, A. Manduca, R. Ehman, J. F. Greenleaf
For over fifteen years there has been significant effort in elastography, which describes the general area of imaging material mechanical properties. Shear vibration elastography uses dynamic tissue displacements to infer material properties from the physics of motion. The method can be used with both magnetic resonance and ultrasound data, which can both be modeled with the time-harmonic, Helmholtz equation if the material is linear, isotropic, incompressible, and piecewise-homogeneous. In this work, we develop a unified perspective on direct Helmholtz inversion. Using the fundamental theorem of statistics and a Gaussian noise model, we present a closed form for the joint conditional probability distribution of the real and imaginary parts of the squared wavenumber given the data and an arbitrary set of weights. An approximate distribution can be used in the case of high SNR which allows a figure-of-merit to be established to objectively compare inversion approaches. Adaptively choosing the inversion weights for each subregion as the smoothed and windowed conjugate of the data results in a narrow conditional probability distribution function and, consequently, high-quality estimates of complex shear modulus. To test the results, we used experimental ultrasound data-collected using a focused 5 MHz transducer with a pulse-repetition frequency of 4 kHz in a block of 15% bovine gel. The gel was harmonically compressed using a signal containing equal amplitudes at frequencies of 200, 300, 400 and 500 Hz. Noise on the measured displacement was estimated from the magnitude of the complex (baseband) correlation function and used with the conditional probability distribution function to report error bars on single-region estimates of complex shear modulus, wave-speed and attenuation.
{"title":"An error analysis of Helmholtz inversion for incompressible shear, vibration elastography with application to filter-design for tissue characterization","authors":"T. Oliphant, R. Kinnick, A. Manduca, R. Ehman, J. F. Greenleaf","doi":"10.1109/ULTSYM.2000.921671","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921671","url":null,"abstract":"For over fifteen years there has been significant effort in elastography, which describes the general area of imaging material mechanical properties. Shear vibration elastography uses dynamic tissue displacements to infer material properties from the physics of motion. The method can be used with both magnetic resonance and ultrasound data, which can both be modeled with the time-harmonic, Helmholtz equation if the material is linear, isotropic, incompressible, and piecewise-homogeneous. In this work, we develop a unified perspective on direct Helmholtz inversion. Using the fundamental theorem of statistics and a Gaussian noise model, we present a closed form for the joint conditional probability distribution of the real and imaginary parts of the squared wavenumber given the data and an arbitrary set of weights. An approximate distribution can be used in the case of high SNR which allows a figure-of-merit to be established to objectively compare inversion approaches. Adaptively choosing the inversion weights for each subregion as the smoothed and windowed conjugate of the data results in a narrow conditional probability distribution function and, consequently, high-quality estimates of complex shear modulus. To test the results, we used experimental ultrasound data-collected using a focused 5 MHz transducer with a pulse-repetition frequency of 4 kHz in a block of 15% bovine gel. The gel was harmonically compressed using a signal containing equal amplitudes at frequencies of 200, 300, 400 and 500 Hz. Noise on the measured displacement was estimated from the magnitude of the complex (baseband) correlation function and used with the conditional probability distribution function to report error bars on single-region estimates of complex shear modulus, wave-speed and attenuation.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131141236","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}
Pub Date : 2000-11-01DOI: 10.1109/ULTSYM.2000.922666
G. Kaduchak, D. Sinha
A simple method which does not require calibration with a reference liquid for the determination of attenuation and density of a fluid contained within a thin-walled cell is demonstrated. The method relies on temporally filtering the impulse response of the system to partially deconvolve the transfer function associated with the wall. Experiments are conducted on cells of differing material construction and wall thickness which demonstrate the effectiveness of this method in obtaining accurate near-field measurements of density and attenuation.
{"title":"Effects of diffraction on the measurement of the acoustic properties of liquids in thin-walled containers","authors":"G. Kaduchak, D. Sinha","doi":"10.1109/ULTSYM.2000.922666","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.922666","url":null,"abstract":"A simple method which does not require calibration with a reference liquid for the determination of attenuation and density of a fluid contained within a thin-walled cell is demonstrated. The method relies on temporally filtering the impulse response of the system to partially deconvolve the transfer function associated with the wall. Experiments are conducted on cells of differing material construction and wall thickness which demonstrate the effectiveness of this method in obtaining accurate near-field measurements of density and attenuation.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134574083","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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