A study of phased array transducer topology for superharmonic imaging

2010 IEEE International Ultrasonics Symposium Pub Date : 2010-12-01 DOI:10.1109/ULTSYM.2010.5935889

P. van Neer, G. Matte, M. Danilouchkine, M. Verweij, N. de Jong

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引用次数: 4

Abstract

Since its introduction in the 90s, tissue 2nd harmonic imaging has become the standard in medical ultrasound. Recently, superharmonic imaging (SHI) was introduced. It targets the combination of the 3rd till 5th harmonics. SHI offers increased spatial resolution, lower sidelobes and less artifacts compared to 2nd harmonic imaging. However, a system for SHI has to deal with the lower energy content of the higher harmonics. The broad bandwidth (−6 dB > 130%) required for SHI prompts for an unconventional phased array design. One of the solutions divides the transmit and receive parts into separate acoustic stacks. Such a design reduces the surface area available for reception. Firstly, we investigate the blockwise and interleaved distribution (topology) of the transmit and receive elements in terms of beam characteristics. Secondly, we research the optimal ratio between transmit and receive elements to increase the area dedicated to receiving while retaining a high quality beam. The latter was assessed using the grating lobe to main beam ratio. The acoustic fields were computed using a combination of numerical methods. FIELD II was used to determine the locations and the peak pressure in the fundamental main and grating lobes. The pressure levels of the harmonics in the main and grating lobes were calculated using the INCS method and Burger's equation, respectively. 3 cycle Gaussian apodized sine bursts were used in transmission. The MI was 1.5 at the transmit frequency of 1.2 MHz — optimal for cardiac SHI. The interleaved topology produces the best defined beam (straight and with low sidelobe levels) compared to the blockwise topologies. Consequently, the main to grating lobe ratios for the different harmonic components were calculated for the interleaved topologies only. The 1/2 till 1/7 interleaved topologies provided enough dynamic range (40 dB) for SHI with 1/7 maximizing the surface area for reception. This increases the SNR by 5 dB.

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用于超谐波成像的相控阵换能器拓扑研究

自20世纪90年代引入以来，组织二次谐波成像已成为医学超声的标准。近年来，超谐波成像(SHI)被引入。它的目标是三到五次谐波的组合。与二次谐波成像相比，SHI提供了更高的空间分辨率、更低的副瓣和更少的伪影。然而，SHI系统必须处理高次谐波的低能量含量。对于非常规相控阵设计，SHI提示所需的宽带宽(- 6 dB > 130%)。其中一个解决方案是将发射和接收部分分成单独的声学堆栈。这样的设计减少了可用于接收的表面积。首先，我们从波束特性的角度研究了发射和接收单元的块状和交错分布(拓扑)。其次，我们研究了发射和接收元件之间的最佳比例，以增加专用接收面积，同时保持高质量的波束。后者是用光栅瓣与主束比来评估的。声场计算采用数值计算相结合的方法。利用FIELD II确定了基本主瓣和光栅瓣的位置和峰值压力。分别用INCS法和Burger方程计算了主瓣和光栅瓣的谐波压力水平。传输时采用3周期高斯离化正弦脉冲。在1.2 MHz的发射频率下，MI为1.5，这是心脏性SHI的最佳选择。与块拓扑相比，交错拓扑产生最佳定义的波束(直且具有低旁瓣电平)。因此，仅对交错拓扑计算了不同谐波分量的主瓣与光栅瓣之比。1/2至1/7交错拓扑结构为SHI提供了足够的动态范围(40 dB)，其中1/7使接收表面积最大化。这使信噪比增加了5 dB。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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2010 IEEE International Ultrasonics Symposium

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