Electrical and Computer Engineering, Southern Methodist University, Dallas, TX 75205, USA.
Sensors (Basel). 2023 Mar 13;23(6):3090. doi: 10.3390/s23063090.
A compact and planar imaging system was developed using a flexible polymer substrate that can distinguish subcutaneous tissue abnormalities, such as breast tumors, based on electromagnetic-wave interactions in materials where permittivity variations affect wave reflection. The sensing element is a tuned loop resonator operating in the industrial, scientific, and medical (ISM) band at 2.423 GHz, providing a localized high-intensity electric field that penetrates into tissues with sufficient spatial and spectral resolutions. The resonant frequency shifts and magnitudes of the reflection coefficients indicate the boundaries of abnormal tissues under the skin due to their high contrasts to normal tissues. The sensor was tuned to the desired resonant frequency with a reflection coefficient of -68.8 dB for a radius of 5.7 mm, with a tuning pad. Quality factors of 173.1 and 34.4 were achieved in simulations and measurements in phantoms. An image-processing method was introduced to fuse raster-scanned 9 × 9 images of resonant frequencies and reflection coefficients for image-contrast enhancement. The results showed a clear indication of the tumor's location at a depth of 15 mm and the capability to identify two tumors both at the depth of 10 mm. The sensing element can be expanded to a four-element phased array for deeper field penetration. Field analysis showed the depths of -20 dB attenuation were improved from 19 to 42 mm, giving wider coverage in tissues at resonance. Results showed that a quality factor of 152.5 was achieved and a tumor could be identified at a depth of up to 50 mm. In this work, simulations and measurements were conducted to validate the concept, showing great potential for subcutaneous imaging in medical applications in a noninvasive, efficient, and lower-cost way.
开发了一种使用柔性聚合物衬底的紧凑平面成像系统，该系统可以根据介电常数变化影响波反射的材料中的电磁波相互作用，区分皮下组织异常，如乳房肿瘤。传感元件是一个调谐环形谐振器，在工业、科学和医疗（ISM）频段 2.423 GHz 下工作，提供局部高强度电场，能够以足够的空间和光谱分辨率穿透组织。由于与正常组织的对比度高，谐振频率的偏移和反射系数的幅度表明了皮肤下异常组织的边界。通过在调谐垫上调谐传感器到所需的谐振频率，半径为 5.7mm 时的反射系数为-68.8dB，实现了模拟和体模测量中的 173.1 和 34.4 的品质因数。引入了一种图像处理方法来融合谐振频率和反射系数的光栅扫描 9×9 图像，以增强图像对比度。结果表明，在 15mm 的深度处清楚地指示了肿瘤的位置，并且能够识别两个均位于 10mm 深度处的肿瘤。传感元件可以扩展为四元件相控阵，以实现更深的场穿透。场分析表明，-20dB 衰减的深度从 19mm 提高到 42mm，在共振时在组织中具有更宽的覆盖范围。结果表明，实现了 152.5 的品质因数，并且可以在深度达 50mm 处识别肿瘤。在这项工作中，进行了模拟和测量以验证该概念，展示了在医学应用中以非侵入性、高效和低成本方式进行皮下成像的巨大潜力。
