Purpose: A novel image-based method for speed of sound (SoS) estimation is proposed and experimentally validated on a tissue-mimicking ultrasound phantom and normal human liver in vivo using linear and curved array tr...Purpose: A novel image-based method for speed of sound (SoS) estimation is proposed and experimentally validated on a tissue-mimicking ultrasound phantom and normal human liver in vivo using linear and curved array transducers. Methods: When the beamforming SoS settings are adjusted to match the real tissue’s SoS, the ultrasound image at regions of interest will be in focus and the image quality will be optimal. Based on this principle, both a tissue-mimicking ultrasound phantom and normal human liver in vivo were used in this study. Ultrasound image was acquired using different SoS settings in beamforming channels ranging from 1420 m/sec to 1600 m/sec. Two regions of interest (ROIs) were selected. One was in a fully developed speckle region, while the other contained specular reflectors. We evaluated the image quality of these two ROIs in images acquired at different SoS settings in beamforming channels by using the normalized autocorrelation function (ACF) of the image data. The values of the normalized ACF at a specific lag as a function of the SoS setting were computed. Subsequently, the soft tissue’s SoS was determined from the SoS setting at the minimum value of the normalized ACF. Results: The value of the ACF as a function of the SoS setting can be computed for phantom and human liver images. SoS in soft tissue can be determined from the SoS setting at the minimum value of the normalized ACF. The estimation results show that the SoS of the tissue-mimicking phantom is 1460 m/sec, which is consistent with the phantom manufacturer’s specification, and the SoS of the normal human liver is 1540 m/sec, which is within the range of the SoS in a healthy human liver in vivo. Conclusion: Soft tissue’s SoS can be determined by analyzing the normalized ACF of ultrasound images. The method is based on searching for a minimum of the normalized ACF of ultrasound image data with a specific lag among different SoS settings in beamforming channels.展开更多
The multimodal admittance method and its improvement are presented to deal with various aspects in underwater acoustics,mostly for the sound propagation in inhomogeneous waveguides with sound-speed profiles,arbitrary-...The multimodal admittance method and its improvement are presented to deal with various aspects in underwater acoustics,mostly for the sound propagation in inhomogeneous waveguides with sound-speed profiles,arbitrary-shaped liquid-like scatterers,and range-dependent environments.In all cases,the propagation problem governed by the Helmholtz equation is transformed into initial value problems of two coupled first-order evolution equations with respect to the modal components of field quantities(sound pressure and its derivative),by projecting the Helmholtz equation on a constructed orthogonal and complete local basis.The admittance matrix,which is the modal representation of Direchlet-to-Neumann operator,is introduced to compute the first-order evolution equations with no numerical instability caused by evanescent modes.The fourth-order Magnus scheme is used for the numerical integration of differential equations in the numerical implementation.The numerical experiments of sound field in underwater inhomogeneous waveguides generated by point sources are performed.Besides,the numerical results computed by simulation software COMSOL Multiphysics are given to validate the correction of the multimodal admittance method.It is shown that the multimodal admittance method is an efficient and stable numerical method to solve the wave propagation problem in inhomogeneous underwater waveguides with sound-speed profiles,liquid-like scatterers,and range-dependent environments.The extension of the method to more complicated waveguides such as horizontally stratified waveguides is available.展开更多
Objective:To calibrate a Quantitative Ultrasonography(QUS)system against densitometryby defining the sensitivity and specificity of the method,and to propose a series of QUS interpre-tation thresholds to classify the ...Objective:To calibrate a Quantitative Ultrasonography(QUS)system against densitometryby defining the sensitivity and specificity of the method,and to propose a series of QUS interpre-tation thresholds to classify the individual risk with regards to the risk of developing osteoporosisin later life.Methods:Subjects were recruited in New York City over a 1-year period.Women with amen-orrhea for at least 12 months were defined as postmenopausal,and all other women as premeno-pausal.Bone mineral density(BMD)was measured with a dual energy X-ray absorptiometer(DXA)and QUS performed with the calcaneus of broadband ultrasound attenuation(BUA)andspeed of sound(SOS)using the Lunar Achilles system.Statistical analysis was performed usingSPSS software Version 10.0.Results:Two hundred twenty-eight premenopausal and menopausal women were recruited.Most of the participants were Hispanic,Caucasian and African-American in this study.All thesubjects had DXA and QUS examined and T-score was got from both.The statistical resultsshowed that the T-score of QUS has a significant relationship with that of DXA(spine:r=0.557,P<0.0001;femur:r=0.611,P<0.0001).Both QUS and DXA T-score has a significant andnegative relationship with age(QUS:r=-0.241,P<0.0001;Spine:r=-0.277,P<0.0001;femur:-0.296,P<0.0001).When T-score of heel ultrasound -1.5 was set as the interpreta-tion threshold,the osteoporosis patients with T-score of DXA-femur scan(100%)and DXA-spine(77.10%)less than -2.5 were detected.As well,the specificities of T-score -1.5 ofQUS for DXA-femur and DXA-spine were 67.5% and 72.8%,respectively.In addition,if we set-1.0 of T-score of QUS as the cutoff,74.80% and 79.60% of the osteopenia based on DXA ofspine and femur were identified.The specificities were 59.4% and 57.7%.Conclusions:QUS of the calcaneus may be an effective method for providing risk stratifica-tion for osteoporosis,and for the closely associated future risk for fragility-fracture.展开更多
Generalized equation for linear gravity waves in moving medium has been obtained. Sound wave is considered as a particular case and it is shown that in inhomogeneous medium at rest it is propagated in full concordance...Generalized equation for linear gravity waves in moving medium has been obtained. Sound wave is considered as a particular case and it is shown that in inhomogeneous medium at rest it is propagated in full concordance with the Doppler law and principle of motion relativity, i.e. these laws are invariant with reference to properties of medium (homogeneity or inhomogeneity). In moving medium they are fair only in the case of its homogeneity. In strongly inhomogeneous moving medium, propagation of sound is absolutely impossible.展开更多
Hand-held implementations of recently intro- duced real-time volumetric tomography approaches repre- sent a promising path toward clinical translation of the optoacoustic technology. To this end, rapid acquisition of ...Hand-held implementations of recently intro- duced real-time volumetric tomography approaches repre- sent a promising path toward clinical translation of the optoacoustic technology. To this end, rapid acquisition of optoacoustic image data with spherical matrix arrays has attained exquisite visualizations of three-dimensional vascular morphology and function deep in human tissues. Nevertheless, significant reconstruction inaccuracies may arise from speed of sound （SOS） mismatches between the imaged tissue and the coupling medium used to propagate the generated optoacoustic responses toward the ultra- sound sensing elements. Herein, we analyze the effects of SoS variations in three-dimensional hand-held tomo- graphic acquisition geometries. An efficient graphics processing unit （GPU）-based reconstruction framework is further proposed to mitigate the SoS-related image quality degradation without compromising the high-frame-rate volumetric imaging performance of the method, essential for real-time visualization during hand-held scans.展开更多
文摘Purpose: A novel image-based method for speed of sound (SoS) estimation is proposed and experimentally validated on a tissue-mimicking ultrasound phantom and normal human liver in vivo using linear and curved array transducers. Methods: When the beamforming SoS settings are adjusted to match the real tissue’s SoS, the ultrasound image at regions of interest will be in focus and the image quality will be optimal. Based on this principle, both a tissue-mimicking ultrasound phantom and normal human liver in vivo were used in this study. Ultrasound image was acquired using different SoS settings in beamforming channels ranging from 1420 m/sec to 1600 m/sec. Two regions of interest (ROIs) were selected. One was in a fully developed speckle region, while the other contained specular reflectors. We evaluated the image quality of these two ROIs in images acquired at different SoS settings in beamforming channels by using the normalized autocorrelation function (ACF) of the image data. The values of the normalized ACF at a specific lag as a function of the SoS setting were computed. Subsequently, the soft tissue’s SoS was determined from the SoS setting at the minimum value of the normalized ACF. Results: The value of the ACF as a function of the SoS setting can be computed for phantom and human liver images. SoS in soft tissue can be determined from the SoS setting at the minimum value of the normalized ACF. The estimation results show that the SoS of the tissue-mimicking phantom is 1460 m/sec, which is consistent with the phantom manufacturer’s specification, and the SoS of the normal human liver is 1540 m/sec, which is within the range of the SoS in a healthy human liver in vivo. Conclusion: Soft tissue’s SoS can be determined by analyzing the normalized ACF of ultrasound images. The method is based on searching for a minimum of the normalized ACF of ultrasound image data with a specific lag among different SoS settings in beamforming channels.
文摘The multimodal admittance method and its improvement are presented to deal with various aspects in underwater acoustics,mostly for the sound propagation in inhomogeneous waveguides with sound-speed profiles,arbitrary-shaped liquid-like scatterers,and range-dependent environments.In all cases,the propagation problem governed by the Helmholtz equation is transformed into initial value problems of two coupled first-order evolution equations with respect to the modal components of field quantities(sound pressure and its derivative),by projecting the Helmholtz equation on a constructed orthogonal and complete local basis.The admittance matrix,which is the modal representation of Direchlet-to-Neumann operator,is introduced to compute the first-order evolution equations with no numerical instability caused by evanescent modes.The fourth-order Magnus scheme is used for the numerical integration of differential equations in the numerical implementation.The numerical experiments of sound field in underwater inhomogeneous waveguides generated by point sources are performed.Besides,the numerical results computed by simulation software COMSOL Multiphysics are given to validate the correction of the multimodal admittance method.It is shown that the multimodal admittance method is an efficient and stable numerical method to solve the wave propagation problem in inhomogeneous underwater waveguides with sound-speed profiles,liquid-like scatterers,and range-dependent environments.The extension of the method to more complicated waveguides such as horizontally stratified waveguides is available.
基金Supported by National Institutes of Health Grants R29-AG14715,PO1-DK 42618 & RO1 37352.
文摘Objective:To calibrate a Quantitative Ultrasonography(QUS)system against densitometryby defining the sensitivity and specificity of the method,and to propose a series of QUS interpre-tation thresholds to classify the individual risk with regards to the risk of developing osteoporosisin later life.Methods:Subjects were recruited in New York City over a 1-year period.Women with amen-orrhea for at least 12 months were defined as postmenopausal,and all other women as premeno-pausal.Bone mineral density(BMD)was measured with a dual energy X-ray absorptiometer(DXA)and QUS performed with the calcaneus of broadband ultrasound attenuation(BUA)andspeed of sound(SOS)using the Lunar Achilles system.Statistical analysis was performed usingSPSS software Version 10.0.Results:Two hundred twenty-eight premenopausal and menopausal women were recruited.Most of the participants were Hispanic,Caucasian and African-American in this study.All thesubjects had DXA and QUS examined and T-score was got from both.The statistical resultsshowed that the T-score of QUS has a significant relationship with that of DXA(spine:r=0.557,P<0.0001;femur:r=0.611,P<0.0001).Both QUS and DXA T-score has a significant andnegative relationship with age(QUS:r=-0.241,P<0.0001;Spine:r=-0.277,P<0.0001;femur:-0.296,P<0.0001).When T-score of heel ultrasound -1.5 was set as the interpreta-tion threshold,the osteoporosis patients with T-score of DXA-femur scan(100%)and DXA-spine(77.10%)less than -2.5 were detected.As well,the specificities of T-score -1.5 ofQUS for DXA-femur and DXA-spine were 67.5% and 72.8%,respectively.In addition,if we set-1.0 of T-score of QUS as the cutoff,74.80% and 79.60% of the osteopenia based on DXA ofspine and femur were identified.The specificities were 59.4% and 57.7%.Conclusions:QUS of the calcaneus may be an effective method for providing risk stratifica-tion for osteoporosis,and for the closely associated future risk for fragility-fracture.
文摘Generalized equation for linear gravity waves in moving medium has been obtained. Sound wave is considered as a particular case and it is shown that in inhomogeneous medium at rest it is propagated in full concordance with the Doppler law and principle of motion relativity, i.e. these laws are invariant with reference to properties of medium (homogeneity or inhomogeneity). In moving medium they are fair only in the case of its homogeneity. In strongly inhomogeneous moving medium, propagation of sound is absolutely impossible.
文摘Hand-held implementations of recently intro- duced real-time volumetric tomography approaches repre- sent a promising path toward clinical translation of the optoacoustic technology. To this end, rapid acquisition of optoacoustic image data with spherical matrix arrays has attained exquisite visualizations of three-dimensional vascular morphology and function deep in human tissues. Nevertheless, significant reconstruction inaccuracies may arise from speed of sound （SOS） mismatches between the imaged tissue and the coupling medium used to propagate the generated optoacoustic responses toward the ultra- sound sensing elements. Herein, we analyze the effects of SoS variations in three-dimensional hand-held tomo- graphic acquisition geometries. An efficient graphics processing unit （GPU）-based reconstruction framework is further proposed to mitigate the SoS-related image quality degradation without compromising the high-frame-rate volumetric imaging performance of the method, essential for real-time visualization during hand-held scans.
