A new method to increase the signal-to-noise ratio (SNR) of synthetic transmit aperture imaging is investigated. The approach utilizes multiple elements to emulate a spherical wave, and the conventional short excitation pulse is replaced by a linear frequency-modulated (FM) signal. The approach is evaluated in terms of image quality parameters in comparison to linear array imaging. Field II simulations using an 8.5-MHz linear array transducer with 128 elements show an improvement in lateral resolution of up to 30% and up to 10.75% improvement in contrast resolution for the new approach. Measurements are performed using our experimental multichannel ultrasound scanning system, RASMUS. The designed linear FM signal obtains temporal sidelobes below -55 dB, and SNR investigations show improvements of 4-12 dB. A 30 turn (approximate to45%) increase in penetration depth is obtained on a multitarget phantom with 0.5 dB/[cm MHz] attenuation. Furthermore, in vivo images of the abdomen are presented, which demonstrate the clinical application of the new approach.
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机译：研究了一种提高合成发射孔径成像信噪比（SNR）的新方法。该方法利用多个元素来模拟球面波，而传统的短激励脉冲被线性调频（FM）信号代替。与线性阵列成像相比，该方法是根据图像质量参数进行评估的。使用具有128个元件的8.5 MHz线性阵列换能器进行的Field II仿真显示，新方法的横向分辨率提高了30％，对比度分辨率提高了10.75％。使用我们的实验性多通道超声扫描系统RASMUS进行测量。设计的线性FM信号可获得低于-55 dB的时间旁瓣，而SNR研究表明，该增益提高了4-12 dB。在具有0.5 dB / [cm MHz]衰减的多目标体模上，穿透深度增加了30转（大约为45％）。此外，还提供了腹部的体内图像，证明了该新方法的临床应用。
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