摘要

目的：肿瘤组织有其特定的电特性（电导率 和介电常数 ），其与周围正常组织的电特性显示出明显的差异，该差异的产生早于组织的结构性变化的产生。建立相对完善的生物组织的电特性数据库对今后研究根据组织电特性变化诊断早期癌症非常重要。目前，生物组织电特性的数据库是建立在离体组织电特性的基础上的，并不能真是反映体内组织的电特性。因此，研究在体生物组织及癌变组织的电特性尤其重要。生物组织的频率相关的电特性包含电导率 和介电常数 ，它们随着生物组织的生理状态的变化而变化。本文对离体、在体的生物组织和发展过程中的乳腺肿瘤组织的电特性（电导率 和介电常数 ）进行了实验研究，并且对肿瘤组织电特性的变化规律进行了初步探讨。

方法：本文自制了小尺寸电特性测量探头，并采用该探头对生物组织的电特性（电导率 和介电常数 ）进行离体和在体的测量。本文设计的小尺寸探头采用四电极法原理，探头与组织的有效接触体积仅为0.25π mm³，对被测组织创伤小。首先，本文采用该探头测量了离体牛肌肉组织、猪肉肌肉组织和脂肪组织的电特性，分析了温度对离体测量结果的影响。其次，采用该探头对40只裸鼠乳腺癌不同生长时期（1-4周）的电特性进行分阶段分组测量，研究裸鼠乳腺癌发展过程中电特性的变化规律。最后，本文还比较了肿瘤组织电特性在体和离体差异、肿瘤组织电特性与肿瘤大小关系，探讨了肿瘤组织电特性分布与血流分布的关系。

结果：本文的离体测量结果显示牛的离体肌肉组织的沿纤维走向的电导率和介电常数均分别大于逆纤维走向的电导率和介电常数（P>0.05）；猪的离体肌肉组织的电导率和介电常数均分别大于离体的脂肪组织的电导率和介电常数（P<0.05）。乳腺肿瘤发展过程中在体测量的电特性数据结果显示随着乳腺癌的发展，乳腺组织的电导率和介电常数均逐渐增大。对于同一组织的在体、离体的电特性结果进行分析，得到组织离体后电特性逐渐降低的结果；对于不同组织在体的电特性分析，得到肿瘤组织在体的电特性显著大于正常组织（P<0.05）。本文对于肿瘤组织的电特性和肿瘤大小的关系进行了相关性分析，得到了中度线性相关的结果（P<0.01），该结果显示肿瘤尺寸越大，同一频率点的电特性越大的趋势。对于肿瘤组织的电特性与血流分布的关系进行相关性分析，得到肿瘤组织的电特性与血流分布呈显著相关（P<0.01），血流量大的位置，电特性大。

结论：本论文的研究研制了小尺寸电特性测量探头，获取了猪肉、牛肉离体的生物组织电特性测量结果；裸鼠乳腺癌不同生长时期的电特性测量结果表明了在乳腺癌发展过程中的电特性变化。对为今后根据组织在体的电特性诊断早期癌症奠定了数据基础。

Abstract

Objective：Electrical properties (EPs) of cancer tissues including electrical conductivity  and permittivity  differ from normal tissues. These differences occur before the structural change of tissues. It is very important to establish a complete EPs database of biological tissues for early cancer diagnose. At present, the database of the electrical properties of biological tissue is based on the EPs of the ex-vivo tissues, and it cannot reflect the real electrical properties of the tissues inside the body. Therefore, it has great significance to study the EPs of normal biological tissues and cancer tissues. Frequency related electrical properties of biological tissues including electrical conductivity σ and permittivity ε have close connection to its physiological and pathological conditions. In this paper, the electrical properties of breast tumor tissues and normal biological tissues during the cancer development were studied. Meanwhile, the changes of the electrical properties of tumor tissue were also discussed.

Mothed: This study developed a small size insertion-type probe to measure the electrical properties of biological tissues in-vivo and ex-vivo. A four-electrode method is used to design this microprobe and the effective contact volume between the probe and the tissue is only 0.25π mm³. Firstly, this paper used the probe to measure the EPs ( ) of beef muscle tissues, pork muscle tissues and pork adipose tissues. And the influence of temperature on the measurement results was also studied. Then, the electrical properties of 40 nude mice with breast cancer at different growth periods (1-4 weeks) were studied by using this probe. Finally, this paper also analyzed the differences of the electric properties between in-vivo measurements and ex-vivo measurements, the relationship between tumor electrical properties and tumor size, and the relationship between the tumor EPs distribution and blood flow distribution.

Results: There were statistically EPs ( ) differences between fiber orientation and reverse fiber orientation of beef muscle tissues (P<0.05); there were also statistically EPs ( ) differences between pork muscle tissues and pork adipose tissues (P<0.05). The EPs ( ) of the breast tissue were gradually increasing during the tumor growth. And the EPs ( ) of biological tissues decreased after excised. The EPs ( ) of the tumor tissues were significantly greater than that of normal tissues (P<0.05). According to the analyzation of tumor size and EPs, it shows that they were moderate linear correlation (P<0.01). This result showed that the larger the tumor size was, the higher the EPs of the same frequency point were. And the correlation analyze results also shows that the EPs ( ) of tumor tissues were significantly correlated with blood flow distribution (P<0.01).

The large EPs occurred where the higher blood flow was.

Conclusions：This study developed a small size insertion-type probe and obtained the ex-vivo EPs results of pork, beef. The electrical properties results of 40 nude mice with breast cancer at different growth periods showed the changes of electrical properties during the development of breast cancer. The study of this paper lays a data foundation of early cancer diagnosis based on the electrical properties of the body tissues for the future.