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本文从换能器的互易原理出发,利用平面波自易校准法获得换能器的自由场发送电流响应.根据平面活塞型换能器的衍射规律,推导出发射声功率的表达式.由此计算互易换能器在给定驱动电流(或电压)作用下的辐射超声功率.基于上述原理,使用自易校准装置测量了互易换能器的声功率一频率曲线.估计的测量不确定优于±20%. 相似文献
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Adaptive speckle reduction of ultrasound images based on maximum likelihood estimation 总被引:1,自引:0,他引:1
A method has been developed in this paper to gain effective speckle reduction in medical ultrasound images. To exploit full knowledge of the speckle distribution, here maximum likelihood was used to estimate speckle parameters corresponding to its statistical mode. Then the results were incorporated into the nonlinear anisotropic diffusion to achieve adaptive speckle reduction. Verified with simulated and ultrasound images, we show that this algorithm is capable of enhancing features of clinical interest and reduces speckle noise more efficiently than just applying classical filters. To avoid edge contribution, changes of contrast-to-noise ratio of different regions are also compared to investigate the performance of this approach. 相似文献
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在聚焦换能器的会聚球面波自由场互易校准法中,衍射损失修正系数是获得互易常数的一个关键参数。本文利用冲击响应函数积分法系统地计算了超声治疗头、机械扫描B超探头以及多普勒诊断探头的衍射损失系数,得出了一些典型参数下的计算曲线,可供不同类型的聚焦换能器会聚球面波互易校准时引用。与传统的瑞利积分法分析比较显示,本文中所采用的冲击响应函数积分法显著地提高了运算速度,同时基本保持了与瑞利积分算法计算结果的一致性。 相似文献