Abstract：
Objective. In this study, nonlinearly frequency-modulated (NLFM) ultrasound was applied to magneto-acousto-electrical tomography (MAET) to increase the dynamic range of detection.Approach. Generation of NLFM signals using window function method-based on the principle of stationary phase-and piecewise linear frequency modulation method-based on the genetic algorithm-was discussed. The MAET experiment systems using spike, linearly frequency-modulated (LFM), or NLFM pulse stimulation were constructed, and three groups of MAET experiments on saline agar phantom samples were carried out to verify the performance-respectively the sensitivity, the dynamic range, and the longitudinal resolution of detection-of MAET using NLFM ultrasound in comparison to that using LFM ultrasound. Based on the above experiments, a pork sample was imaged by ultrasound imaging method, spike MAET method, LFM MAET method, and NLFM MAET method, to compare the imaging accuracy.Main results. The experiment results showed that, through sacrificing very little main-lobe width of pulse compression or equivalently the longitudinal resolution, the MAET using NLFM ultrasound achieved higher signal-to-interference ratio (and therefore higher detection sensitivity), lower side-lobe levels of pulse compression (and therefore larger dynamic range of detection), and large anti-interference capability, compared to the MAET using LFM ultrasound.Significance. The applicability of the MAET using NLFM ultrasound was proved in circumferences where sensitivity and dynamic range of detection were mostly important and slightly lower longitudinal resolution of detection was acceptable. The study furthered the scheme of using coded ultrasound excitation toward the clinical application of MAET.
摘要：
在这项研究中,将非线性调频（NLFM）超声应用于磁声电断层扫描（MAET），以增加检测的动态范围。讨论了基于固定相位原理的窗函数法和基于遗传算法的分段线性调频法产生NLFM信号的方法。MAET实验系统使用尖峰，线性调频(LFM)，或NLFM脉冲刺激被构建，并对盐水琼脂模型样品进行了三组MAET实验，以验证其性能-分别为灵敏度，动态范围，与使用LFM超声相比，使用NLFM超声检测MAET的纵向分辨率。基于以上实验,通过超声成像方法对猪肉样本进行成像，峰值MAET法，LFMMAET方法，和NLFMMAET方法，比较成像精度。实验结果表明,通过使用很少的主瓣宽度的脉冲压缩或等效的纵向分辨率，使用NLFM超声的MAET实现了更高的信号干扰比（因此更高的检测灵敏度），脉冲压缩的旁瓣水平较低（因此检测的动态范围更大），和大的抗干扰能力，与使用LFM超声的MAET相比。使用NLFM超声的MAET的适用性在检测的灵敏度和动态范围最重要并且检测的纵向分辨率略低的情况下得到了证明。该研究进一步推进了将编码超声激励用于MAET临床应用的方案。
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