Impact of propagation through an aberrating medium on the linear effective apodization of a nonlinearly generated second harmonic field.
Impact of propagation through an aberrating medium on the linear effective apodization of a nonlinearly generated second harmonic field.
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通过像差介质的传播对非线性生成的二次谐波场的线性有效变迹的影响。
DOI：
10.1109/tuffc.2006.1665074
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Miller,JamesG
中科院分区：
文献类型：
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作者：
Wallace,KirkD;Holland,MarkR;Robinson,BrentS;Fedewa,RussellJ;Lloyd,ChristopherW;Miller,JamesG
基于非线性产生的二次谐波信号(组织谐波成像)的技术已经迅速取代线性(基波)成像方法，成为二维超声心动图的标准。非线性产生的二次谐波(2f)场分量相对于基频(1f)场分量的紧凑性的增强被广泛认为是有助于观察到的图像质量改善的因素之一。这项研究的目的是测量通过非均匀组织传播引起的相位和幅度像差对与以下相关的波束宽度的影响：基波(1f)；非线性产生的二次谐波(2f)；以及在相同(2f)频率下线性传播的、有效的变迹信号。通过水听器测量验证了对相控阵成像系统传输特性的修改。结果表明，与线性传输的有效变迹传输情况相关的衍射图特征与非线性产生的二次谐波场的详细空间特性非常一致。腹壁组织像差的影响对于所有三种所研究的光束轮廓都是明显的。与与谐波成像相关的图像质量的改善相一致的是，在插入像差的情况下，经像差的非线性产生的二次谐波光束比相应的经像差的基波图案保持得更紧密。
Techniques based on the nonlinearly generated second harmonic signal (tissue harmonic imaging) have rapidly supplanted linear (fundamental) imaging methods as the standard in two-dimensional echocardiography. Enhancements to the compactness of the nonlinearly generated second harmonic (2f) field component with respect to the fundamental (1f) field component are widely considered to be among the factors contributing to the observed image quality improvements. The objective of this study was to measure the impact of phase and amplitude aberrations resulting from propagation through an inhomogeneous tissue, on the beamwidths associated with: the fundamental (1f); the nonlinearly generated second harmonic (2f); and the linearly propagated, effective apodization signal at the same (2f) frequency. Modifications to the transmit characteristics of a phased-array imaging system were validated with hydrophone measurements. Results demonstrate that the characteristics of the diffraction pattern associated with the linear-propagation effective apodization transmit case were found to be in good agreement with the detailed spatial characteristics of the nonlinearly generated second harmonic field. The effects of the abdominal wall tissue aberrators are apparent for all three of the beam profiles studied. Consistent with the improved image quality associated with harmonic imaging, the aberrated nonlinearly generated second harmonic beam was shown to remain more compact than the corresponding aberrated fundamental beam patterns in the presence of the interposed aberrator.