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An acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction (MAT-MI) is pro-posed,based on the analyses of one-dimensional tissue vibration,three-dimensional acoustic dipole radiation and acoustic waveform detection with a planar piston transducer.The collected waveforms provide information about the conductiv-ity boundaries in various vibration intensities and phases due to the acoustic dipole radiation pattern.Combined with the simplified back projection algorithm,the conductivity configuration of the measured layer in terms of shape and size can be reconstructed with obvious border stripes.The numerical simulation is performed for a two-layer cylindrical phantom model and it is also verified by the experimental results of MAT-MI for a tissue-like sample phantom.The proposed model suggests a potential application of conductivity differentiation and provides a universal basis for the further study of conductivity reconstruction for MAT-MI. 相似文献
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本文从振动声成像的基本原理出发,通过引入点扩展函数PSF和定义轴向响应函数ARF,研究了由凹球面聚焦换能器分割而成的一种典型共焦换能器参数对振动声成像系统侧向分辨率和轴向分辨率的影响。计算研究表明:增大凹球面换能器的口径、减小几何焦距和提高中心频率均可以提高系统的侧向分辨率和轴向分辨率;但改变凹球面换能器的分割比例对两种分辨率影响不尽相同。综合考虑超声换能器激励、聚焦性能以及产生的辐射力效果等因素,则换能器应按等辐射面积原则分割为宜。文中还分析了介质的声衰减系数对实际轴向分辨率的影响。 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
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Focusing Ultrasonic Field of Holed Cap Spherical Shell Transducer Using the Spheroidal Beam Equation 下载免费PDF全文
A large aperture transducer with an inner hole has been used to validate the feasibility of using the spheroidal beam equation to solve the acoustic field of the inner holed transducer.The numerical results of several harmonics are presented for the nonlinear field. 相似文献
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