To develop ultrasound-guided radiotherapy, we proposed an assistant structure with embedded markers along with a novel alternative method, the Aligned Peak Response (APR) method, to alter the conventional delay-and-sum (DAS) beamformer for reconstructing ultrasound images obtained from a flexible array. We simulated imaging targets in Field-II using point target phantoms with point targets at different locations. In the experimental phantom ultrasound images, image RF data were acquired with a flexible transducer with in-house assistant structures embedded with needle targets for testing the accuracy of the APR method. The lateral full width at half maximum (FWHM) values of the objective point target (OPT) in ground truth ultrasound images, APR-delayed ultrasound images with a flat shape, and images acquired with curved transducer radii of 500 mm and 700 mm were 3.96 mm, 4.95 mm, 4.96 mm, and 4.95 mm. The corresponding axial FWHM values were 1.52 mm, 4.08 mm, 5.84 mm, and 5.92 mm, respectively. These results demonstrate that the proposed assistant structure and the APR method have the potential to construct accurate delay curves without external shape sensing, thereby enabling a flexible ultrasound array for tracking pancreatic tumor targets in real time for radiotherapy.
为推进超声引导放疗技术的发展，本研究提出一种内置标记点的辅助结构，并结合新型替代方法——对齐峰值响应法，以改进传统延迟叠加波束成形算法，用于重建柔性阵列获取的超声图像。我们利用Field-II软件对不同位置点目标的仿体进行成像模拟。在实验仿体超声图像采集中，采用内置针状靶标的定制辅助结构柔性换能器获取射频数据，以验证APR方法的定位精度。真实超声图像中目标点靶的横向半高全宽值分别为：平面形态APR延迟图像3.96毫米，曲率半径500毫米和700毫米的弯曲换能器图像分别为4.95毫米、4.96毫米和4.95毫米；对应轴向半高全宽值分别为1.52毫米、4.08毫米、5.84毫米和5.92毫米。实验结果表明，所提出的辅助结构与APR方法无需外部形态传感即可构建精确的延迟曲线，这使柔性超声阵列能够实时追踪胰腺肿瘤靶区，为精准放疗提供技术支持。
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