Novel method for diagnosis of early-stage lung cancer: using metamaterials THz sensors
Schematic diagram of the experimental setup for early-stage lung cancer diagnosis.
The measured THz frequency-domain (FD) transmission spectra of cancer tissue and normal tissue, respectively
Currently, lung cancer has become one of the leading causes of cancer death. In many cases, the lung cancer has already spread beyond the original site by the time the patients have symptoms and seek medical attention. The main reason is that early-stage lung cancer has no obvious symptoms and is very difficult to be definitely diagnosed by general methods including bronchoscopy, mediastinoscopy, biopsy, etc. Moreover, the general methods are complicated or time consuming. Therefore, rapid diagnosis of early-stage lung cancer is of great significance.
Metamaterials (MMs) are artificial composite materials or structures which composed of sub-wavelength resonance unit cells. They have special physical properties which cannot be found in natural materials. Terahertz (THz) sensors based on the MMs are extremely sensitive to the change of surrounding dielectric. Thus they can find wide applications in biomedicine.
Because the refractive index and absorption coefficient of early-stage lung cancer tissues show very little difference from that of the normal tissues, it is very difficult to diagnose early-stage lung cancer. For the first time in the world (to the best knowledge of the authors), the research group led by Prof. Fangrong Hu from Guilin University of Electronic Technology utilized the THz sensors based on MMs to test and diagnose the early-stage lung cancer under the collaboration with Prof. Huasheng Liang from the Ninth Affiliated Hospital of Guangxi Medical University. The results indicated that the THz frequency spectra showed distinct difference when the sensors were covered with normal tissues and early-stage cancer tissues in the same thickness, and the frequency shift was larger when the sensor was covered with cancer tissues. It could provide important theoretical foundation for the diagnosis of early-stage lung cancer. The related research results have been reported in Chinese Optics Letters, Volume 15, No. 11, 2017 (Xin Xu et al., Metamaterials-based terahertz sensor for quick diagnosis of early lung cancer).
The proposed method can distinguish cancer tissues from normal tissues even though they have very close refractive index and absorption coefficient. Compared with conventional medical methods and other THz methods by calculating the tissues’ refractive index and absorption coefficient, the proposed method is very quick, simple, and label-free.
Prof. Hu, the director of the research group, believes that this method is very promising for the diagnosis of not only lung cancer but also some other cancers in early-stage. It promotes the application of THz technology in biomedicine.
Further work will be focused on the design of novel MMs THz sensors with higher sensitivity, and the application in the diagnosis of other cancers in early-stage.
利用新型超材料传感器进行肺癌早期诊断
检测早期肺癌组织的实验装置示意图
实验获得的正常组织和癌变组织的太赫兹频域光谱
肺癌是当前死亡率最高的恶性肿瘤之一，主要原因在于肺癌早期症状不明显，很难发现和诊断，很多病例等到察觉时就已是晚期。目前对早期肺癌的常规检查方法主要有气管镜、纵膈镜和穿刺活检等，这些方法过程繁琐、耗时长。因此，如何及时发现与诊断早期肺癌，已成为当前医学领域急需要解决的问题。
超材料是指通过人工方法制作而成的复合材料或结构，其具有天然材料所不具备的超常物理性质，一般由亚波长尺寸的阵列单元构成谐振结构。基于超材料的太赫兹传感器对周围环境变化极其敏感，这一特性在生物医学中有重要的应用价值。
早期肺癌组织和正常组织的折射率和吸收系数相差很小、难以区分和诊断，针对这一情况，桂林电子科技大学的胡放荣教授课题组与广西医科大学第九附属医院梁华晟教授合作，在国际上首次（据该课题组所知）开展了基于超材料太赫兹传感器的早期肺癌检测与诊断研究，并进行了实验验证。当超材料太赫兹传感器表面分别覆盖同样厚度的正常组织和早期癌变组织时，其太赫兹频域光谱有明显的差异：覆盖癌变组织的传感器谐振峰频移量更大，这为诊断组织癌变提供了重要依据。相关研究成果发表在Chinese Optics Letters 2017 年第11 期上(Xin Xu et al., Metamaterials-based terahertz sensor for quick diagnosis of early lung cancer).
相比于常规医学方法和计算组织折射率、吸收系数的太赫兹检测方法，该课题组提出的方法能区别折射率和吸收系数相差甚微的正常组织和早期癌变组织，并且不需要标记，具有快速、准确和简单的优点。
该课题组的胡放荣教授认为，这一成果对肺癌及其它癌症的早期发现和诊断，促进太赫兹技术在生物医学领域的应用都具有十分重要的意义。
下一步工作将侧重于设计灵敏度更高的超材料太赫兹传感器，并尝试用于其他癌症的早期发现与诊断。