Department of Biomedical Engineering, Pukyong National University, Busan 48513, Korea.
Department of Convergence IT Engineering, Pohang University of Science and Technology, Pohang 37673, Korea.
Sensors (Basel). 2021 Mar 24;21(7):2275. doi: 10.3390/s21072275.
High-frequency ultrasound (HFUS) imaging has emerged as an essential tool for pre-clinical studies and clinical applications such as ophthalmic and dermatologic imaging. HFUS imaging systems based on array transducers capable of dynamic receive focusing have considerably improved the image quality in terms of spatial resolution and signal-to-noise ratio (SNR) compared to those by the single-element transducer-based one. However, the array system still suffers from low spatial resolution and SNR in out-of-focus regions, resulting in a blurred image and a limited penetration depth. In this paper, we present synthetic aperture imaging with a virtual source (SA-VS) for an ophthalmic application using a high-frequency convex array transducer. The performances of the SA-VS were evaluated with phantom and ex vivo experiments in comparison with the conventional dynamic receive focusing method. Pre-beamformed radio-frequency (RF) data from phantoms and excised bovine eye were acquired using a custom-built 64-channel imaging system. In the phantom experiments, the SA-VS method showed improved lateral resolution (>10%) and sidelobe level (>4.4 dB) compared to those by the conventional method. The SNR was also improved, resulting in an increased penetration depth: 16 mm and 23 mm for the conventional and SA-VS methods, respectively. Ex vivo images with the SA-VS showed improved image quality at the entire depth and visualized structures that were obscured by noise in conventional imaging.
高频超声（HFUS）成像已成为临床前研究和临床应用（如眼科和皮肤科成像）的重要工具。与基于单元素换能器的系统相比，基于能够进行动态接收聚焦的阵列换能器的 HFUS 成像系统在空间分辨率和信噪比（SNR）方面显著提高了图像质量。然而，阵列系统在离焦区域仍然存在低空间分辨率和 SNR 的问题，导致图像模糊和穿透深度有限。在本文中，我们提出了一种用于眼科应用的虚拟源合成孔径成像（SA-VS）方法，使用高频凸阵换能器。通过与传统的动态接收聚焦方法进行比较，评估了 SA-VS 的性能，进行了体模和离体实验。使用定制的 64 通道成像系统从体模和切除的牛眼获取预波束形成射频（RF）数据。在体模实验中，与传统方法相比，SA-VS 方法显示出了改善的横向分辨率（>10%）和旁瓣电平（>4.4 dB）。SNR 也得到了提高，从而增加了穿透深度：传统方法和 SA-VS 方法分别为 16mm 和 23mm。使用 SA-VS 的离体图像在整个深度上显示出了改善的图像质量，并可视化了在传统成像中被噪声掩盖的结构。
