Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow G1 1XW, UK.
Sensors (Basel). 2020 Sep 19;20(18):5370. doi: 10.3390/s20185370.
Aperiodic sparse 2D ultrasonic array configurations, including random array, log spiral array, and sunflower array, have been considered for their potential as conformable transducers able to image within a focal range of 30-80 mm, at an operating frequency of 2 MHz. Optimisation of the imaging performance of potential array patterns has been undertaken based on their simulated far field directivity functions. Two evaluation criteria, peak sidelobe level (PSL) and integrated sidelobe ratio (ISLR), are used to access the performance of each array configuration. Subsequently, a log spiral array pattern with -19.33 dB PSL and 2.71 dB ISLR has been selected as the overall optimal design. Two prototype transducers with the selected log spiral array pattern have been fabricated and characterised, one using a fibre composite element composite array transducer (CECAT) structure, the other using a conventional 1-3 composite (C1-3) structure. The CECAT device demonstrates improved coupling coefficient (0.64 to 0.59), reduced mechanical cross-talk between neighbouring array elements (by 10 dB) and improved operational bandwidth (by 16.5%), while the C1-3 device performs better in terms of sensitivity (~50%). Image processing algorithms, such as Hough transform and morphological opening, have been implemented to automatically detect and dimension particles located within a fluid-filled tube structure, in a variety of experimental scenarios, including bespoke phantoms using tissue mimicking material. Experiments using the fabricated CECAT log spiral 2D array transducer demonstrated that this algorithmic approach was able to detect the walls of the tube structure and stationary anomalies within the tube with a precision of ~0.1 mm.
非周期性稀疏二维超声阵列配置，包括随机阵列、对数螺旋阵列和向日葵阵列，因其具有成为顺应性换能器的潜力而受到关注，能够在 30-80mm 的焦域内成像，工作频率为 2MHz。基于其模拟远场指向性函数，对潜在阵列模式的成像性能进行了优化。使用峰值旁瓣电平 (PSL) 和积分旁瓣比 (ISLR) 两个评估标准来评估每个阵列配置的性能。随后，选择对数螺旋阵列模式，其 PSL 为-19.33dB，ISLR 为 2.71dB，作为总体最优设计。使用选定的对数螺旋阵列模式制造并表征了两个原型换能器，一个使用纤维复合材料元件复合阵列换能器 (CECAT) 结构，另一个使用传统的 1-3 复合材料 (C1-3) 结构。CECAT 器件的耦合系数提高了 (0.64 至 0.59)，相邻阵列元件之间的机械串扰降低了 (10dB)，工作带宽提高了 (16.5%)，而 C1-3 器件的灵敏度更好 (~50%)。实现了图像处理算法，如霍夫变换和形态学开运算，以自动检测和确定位于充满流体的管结构内的颗粒的尺寸，包括使用组织模拟材料的定制体模。使用制造的 CECAT 对数螺旋 2D 阵列换能器进行的实验表明，这种算法方法能够以约 0.1mm 的精度检测管结构的壁和管内的静止异常。
