Instituto de Biofísica e Engenharia Biomédica (IBEB), Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016-Lisbon, Portugal.
Sorbonne Université, CNRS, Laboratoire de Génie Electrique et Electronique de Paris, 75252, Paris, France.
Sensors (Basel). 2020 Sep 2;20(17):4968. doi: 10.3390/s20174968.
We produced an anatomically and dielectrically realistic phantom of the axillary region to enable the experimental assessment of Axillary Lymph Node (ALN) imaging using microwave imaging technology. We segmented a thoracic Computed Tomography (CT) scan and created a computer-aided designed file containing the anatomical configuration of the axillary region. The phantom comprises five 3D-printed parts representing the main tissues of interest of the axillary region for the purpose of microwave imaging: fat, muscle, bone, ALNs, and lung. The phantom allows the experimental assessment of multiple anatomical configurations, by including ALNs of different size, shape, and number in several locations. Except for the bone mimicking organ, which is made of solid conductive polymer, we 3D-printed cavities to represent the fat, muscle, ALN, and lung and filled them with appropriate tissue-mimicking liquids. Existing studies about complex permittivity of ALNs have reported limitations. To address these, we measured the complex permittivity of both human and animal lymph nodes using the standard open-ended coaxial-probe technique, over the 0.5 GHz-8.5 GHz frequency band, thus extending current knowledge on dielectric properties of ALNs. Lastly, we numerically evaluated the effect of the polymer which constitutes the cavities of the phantom and compared it to the realistic axillary region. The results showed a maximum difference of 7 dB at 4 GHz in the electric field magnitude coupled to the tissues and a maximum of 10 dB difference in the ALN response. Our results showed that the phantom is a good representation of the axillary region and a viable tool for pre-clinical assessment of microwave imaging technology.
我们制作了一个腋窝区域的解剖学和介电逼真的体模，以能够使用微波成像技术对腋窝淋巴结（ALN）成像进行实验评估。我们对胸部 CT 扫描进行了分割，并创建了一个计算机辅助设计文件，其中包含腋窝区域的解剖结构。该体模包含五个 3D 打印部分，代表腋窝区域用于微波成像的主要感兴趣组织：脂肪、肌肉、骨骼、ALN 和肺。该体模允许通过在多个位置包含不同大小、形状和数量的 ALN 来评估多种解剖结构。除了模拟器官的骨部分，它由固体导电聚合物制成，我们 3D 打印了空腔来代表脂肪、肌肉、ALN 和肺，并在其中填充了适当的组织模拟液体。现有的关于 ALN 复介电常数的研究报告了一些局限性。为了解决这些问题，我们使用标准的开放式同轴探头技术，在 0.5GHz-8.5GHz 频率范围内测量了人类和动物淋巴结的复介电常数，从而扩展了当前关于 ALN 介电特性的知识。最后，我们对构成体模空腔的聚合物的影响进行了数值评估，并将其与真实的腋窝区域进行了比较。结果表明，在 4GHz 时，耦合到组织的电场幅度最大相差 7dB，ALN 响应最大相差 10dB。我们的结果表明，该体模是腋窝区域的良好表示，并且是微波成像技术临床前评估的可行工具。
