Terahertz Spectroscopy Study Of Tissue And Plasma In External Irradiation Injury

Terahertz（THz）wave is an electromagnetic wave with a frequency range of 0.1～10 THz(1 THz=10¹² Hz)and a wavelength range from 0.03-3 mm.Terahertz waves are very sensitive to the low-frequency vibration of molecules,and many biological macromolecules have vibrational and rotational frequencies within the THz band interval.Therefore,the THz wave can be used to obtain rich biological and material information,as an ideal non-destructive analysis for biological tissues and cells.Terahertz time-domain spectroscopy（THz-TDS）,as an advancing technology developed in recent years,has unique advantages such as high resolution,spectral fingerprint,large bandwidth,and low photon energy.THz-TDS has been widely used in the field of biomedicine,with its great potential applications in exploring rapid,sensitive,and non-destructive detection and diagnosis of radiation-sensitive substances.Research Objectives:1)Use terahertz time-domain spectroscopy technology to explore the spectral characteristics of different tissues of BALB/c mice after ionizing radiation,in order to provide a new detection technology for the pathological detection of radiation diseases.2)Use terahertz time-domain spectroscopy technology to explore the spectral characteristics of BALB/c mouse plasma after ionizing radiation,integrate different classification and identification models,and establish an effective THz spectral plasma classification model to assess radiation does and degree of damage.In the event of an accident,such technology can provide large-scale dose estimation in a population with a new method.Experimental Methods:1)The experimental animals were irradiated with different doses of ⁶⁰Co-γrays to construct animal models,and multiple tissues were embedded in paraffin.The terahertz time-domain spectra of paraffin sections were detected by transmission mode,and the Hematoxylin-Eosin（HE）staining pathology was used to verify the reliability of THz technology.2)The experimental animals were irradiated with 6 Gy ⁶⁰Co-γrays.At different time points,the THz-ATR mode was used to detect the terahertz spectrum of normal plasma and irradiated plasma,and then the content of terahertz characteristic absorbing molecules was determined.3)The experimental animals were irradiated with different doses of ⁶⁰Co-γrays,the THz-ATR mode was used to detect the terahertz spectrum of normal plasma and irradiated plasma,and the content of different biomolecules was also determined.and the Savitzky-Golay convolution smoothing method and z-score normalization method were used,combined with principal component analysis（PCA）and other analytical methods for spectral preprocessing and followed by combination of KNN,SVM and RF classification models to compare the classification performance.Results:1)By comparing and analyzing the tissue time-domain spectrum,we found that the amplitude in the time-domain spectrum can better reflect the difference between normal tissue and radiation-damaged tissue.The refractive index spectrum in the 0.5-2.5 THz frequency band was selected and compared with the pathological diagnosis results,indicating that the THz spectral characteristics can reflect the ionizing radiation damage of different tissues to a certain extent.2)Compared with the sham exposure group,the experimental group had the highest absorption coefficient and dielectric loss of plasma after 4 hours at 6 Gy irradiation;the refractive index and dielectric constant were the lowest,and the spectral difference was the most significant.Sensitive biomolecules were all significantly different.The above findings provide reliable time points for subsequent dose-effect studies.3)At 0-6 Gy,the absorption coefficient and dielectric loss increased,and the refractive index and dielectric constant decreased with increasing dose;Spectral parameters are all between 4-6 Gy.Compared with the sham exposure group,the spectral parameters of the 6 Gy exposure group had the most significant differences.As for the occurrence of 8 Gy,it may be caused by the difference in DNase I content after irradiation.The classification model was established for different doses of plasma,and it was found that the classification effectiveness was the best for models with the direct KNN,without normalization of the plasma dielectric loss,and without PCA.Conclusion:To a certain extent,the use of terahertz time-domain spectroscopy can provide a new detection technology for the pathological detection of radiation diseases and estimate radiation does in a fast and effective matter.