Establishment of sentinel lymph node detection using impedance CT

对手术切除的器官进行电评估，以确定正常组织和恶性病变之间是否存在电差异。具体地，评估正常胃粘膜和恶性病变的介电特性，并计算“tan δm”，即β分散范围内的最大tan δ。正常胃粘膜与高分化腺癌恶性病变之间的tan δm值无显著性差异。而低分化腺癌患者正常胃粘膜的tan δm为3.35 ± 0.21，肿瘤深度为m ~ mp的病变为4.66 ± 0.79，肿瘤深度为ss ~ se的病变为7.60 ± 1.23，差异有统计学意义。在组织学上，“tan δm”显示在结构变化方面对于显著低分化或晚期肿瘤更高。同时，通过改变胶体直径、含量、剂量、给药时间和测量时间，尝试使用铁胶体进行淋巴结积聚的电检测，但在正常淋巴结和含铁淋巴结之间未观察到电差异。另外，使用接触式多点测定用电极和现有的阻抗分析仪（HP 4194 A），在1 kHz ~ 1 MHz的多频率范围内测定实验动物胃和大肠的介电特性。然而，数据的可重复性很差，结果被认为反映了动物之间的个体差异。虽然基于使用等电位反投影获得的数据创建了介电特性的电导率分布图，但由于空间分辨率不足，在获得的图像上无法可视化淋巴结。基于以上所述，尽管在正常组织和癌组织之间可能存在电学差异，但是在实践中可能证明难以建立使用阻抗CT的前哨淋巴结检测。

Electrical evaluation of surgically resected organs was conducted to determine whether electrical differences exist between normal tissue and malignant lesions. Specifically, dielectric properties of normal gastric mucosa and malignant lesions were evaluated, and "tan δm", the maximum tan δ in the β dispersion range, was calculated. No significant differences were observed in "tan δm" between normal gastric mucosa and malignant lesions in patients with well-differentiated adenocarcinoma. However, in patients with poorly differentiated adenocarcinoma, "tan δm" was 3.35 ± 0.21 in normal gastric mucosa, 4.66 ± 0.79 in lesions with tumor depths of m to mp, and 7.60 ± 1.23 in areas with tumor depths of ss to se, indicating statistically significant differences. Histologically, "tan δm" was shown to be higher for markedly poorly differentiated or advanced tumors in terms of structural changes. Meanwhile, electrical detection of lymph node accumulation using iron colloids was attempted by altering colloid diameter, content, dose, administration time, and measurement time, but no electrical differences were observed between normal lymph nodes and lymph nodes containing iron. In addition, the dielectric properties of experimental animal stomachs and large intestines were measured in a multi-frequency range from 1 kHz to 1 MHz using electrodes for contact-type multiple-point measurements and an existing impedance analyzer (HP4194A). However, data reproducibility was poor, and the results were thought to reflect individual differences among animals. Although a conductivity distribution map of dielectric properties was created based on obtained data using equipotential back-projection, lymph nodes could not be visualized on obtained images due to insufficient spatial resolution. Based on the above, although electrical differences may exist between normal and cancer tissues, establishment of sentinel lymph node detection using impedance CT in practice may prove difficult.