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
为了研究室外视距(line of sight,Lo S)和非视距(non-Lo S,NLo S)传输场景中车辆与车辆(vehicle-to-vehicle,V2V)之间的无线通信系统,提出一种基于几何街道散射场景的统计信道模型,其发射端和接收端都处于移动状态。先假设有无穷多的散...为了研究室外视距(line of sight,Lo S)和非视距(non-Lo S,NLo S)传输场景中车辆与车辆(vehicle-to-vehicle,V2V)之间的无线通信系统,提出一种基于几何街道散射场景的统计信道模型,其发射端和接收端都处于移动状态。先假设有无穷多的散射体随机分布在街道两侧;并且在发射端和接收端都采用多天线技术,然后模型定量给出了几何街道散射场景下到发射角(angle of arrival,AOD)和到达角(angle of arrival,AOA)之间的几何关系。同时研究了信号在几何散射信道模型中的空间互相关函数、时间自相关函数(autocorrelation function,ACF)、频率互相关函数以及多普勒功率谱密度(power spectral density,PSD)的影响。理论分析和仿真结果表明提出的V2V通信系统的无线信道的统计特性符合理论和经验,拓展了多输入多输出宽带V2V通信系统的研究。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.
文摘为了研究室外视距(line of sight,Lo S)和非视距(non-Lo S,NLo S)传输场景中车辆与车辆(vehicle-to-vehicle,V2V)之间的无线通信系统,提出一种基于几何街道散射场景的统计信道模型,其发射端和接收端都处于移动状态。先假设有无穷多的散射体随机分布在街道两侧;并且在发射端和接收端都采用多天线技术,然后模型定量给出了几何街道散射场景下到发射角(angle of arrival,AOD)和到达角(angle of arrival,AOA)之间的几何关系。同时研究了信号在几何散射信道模型中的空间互相关函数、时间自相关函数(autocorrelation function,ACF)、频率互相关函数以及多普勒功率谱密度(power spectral density,PSD)的影响。理论分析和仿真结果表明提出的V2V通信系统的无线信道的统计特性符合理论和经验,拓展了多输入多输出宽带V2V通信系统的研究。
