太赫兹波光声效应诊断皮肤癌仿真分析(特邀)

Simulation Analysis of Skin Cancer Diagnosis Using Terahertz-waves Photoacoustic Effect(Invited)

随着太赫兹源的发展,利用组织的太赫兹波光声效应以非入侵方式对病变组织进行区分检测展现了巨大优势。通过有限元方法仿真分析了在1.0 THz下皮肤及皮肤癌的热效应与光声效应,并通过光声信号对不同生长时期的基底细胞癌进行分析。仿真结果表明,可以通过光声信号有效区分不同皮肤结构与不同基底细胞癌生长时期。该结果揭示了利用太赫兹波光声效应实现早期皮肤癌的太赫兹无损诊断的应用价值。

In recent years,Terahertz-waves have brought a brand-new,label-free,non-invasive detection method to biomedical research due to their non-ionization,broadband,and high signal-to-noise ratio.With the development of Terahertz sources,especially the generation of Terahertz pulses with energy up to mJ,the study of biological tissues in Terahertz band is no longer limited to non-thermal effects.Histopathological test is considered as the gold standard for diagnosing skin cancer and other tumors.However,the borders of some tumors are blurred,which may result in excessive surgery,mistaken resection,or inability to fully resection in the process of histopathological test.It is of great value to combine the physical properties of skin tissue and Basal Cell Carcinoma(BCC)with their optical properties in the Terahertz band for the non-destructive diagnosis of skin cancer.The purpose of this paper is to provide a certain theoretical basis for the non-destructive detection of early skin cancer by studying the photoacoustic effect of Terahertz-Waves in in vivo tissues(normal skin tissue,skin tissue containing basal cell carcinoma).In this paper,according to the dendritic growth law of basal cell carcinoma in the basal layer of skin tissue,combined with the absorption characteristics of skin tissue in the Terahertz band and the difference in water content between skin tissues,a skin tissue model containing basal cell carcinoma is established.The model includes the stratum corneum,epidermis,and lesions of different basal cell carcinomas.As a control,a structural model of normal skin tissue is also established.Using the Pennes heat transfer equation,the Terahertz radiative heat effects of normal skin tissue models and skin tissue models containing basal cell carcinoma are analyzed.Finally,the differences and components of photoacoustic signals between normal skin tissue models and skin tissue models containing different basal cell carcinoma growth stages are analyzed using the photoacoustic effect of Terahertz-Waves.The simulation results show that the absorption of Terahertz-Waves in the epidermis is most obvious.It is difficult for high-energy pulsed terahertz waves to penetrate deep into the dermis for both normal skin tissue and skin tissue containing basal cell carcinoma.However,there are significant differences in thermal effects between skin tissue containing basal cell carcinoma and normal skin tissue.Skin tissue containing basal cell carcinomas is more sensitive to temperature changes from Terahertz-Waves irradiation.The analysis of different basal cell carcinoma growth stages shows that the temperature response of Terahertz-Waves could be used to detect the growth changes of basal cell carcinomas.As basal cell carcinomas spread and grow in skin tissue,it is easier to distinguish the different basal cell carcinoma growth phases by thermal effects.Furthermore,rapid diagnosis of basal cell carcinoma can be achieved by Terahertz-Waves irradiation with a single pulse energy of the order ofμJ.Analysis of the difference in the photoacoustic signals between the two models shows that the skin tissue containing basal cell carcinoma produces stronger photoacoustic signals than normal skin tissue.As basal cell carcinoma spreads and grows,the photoacoustic signal received on the outer surface of the skin has a greater amplitude,and the photoacoustic signal generated by the stratum corneum and epidermis decays faster,which make it easier to detect and analyze.The findings are suitable for non-destructive diagnosis of early-stage skin cancer by Terahertz-Waves.The application value of Terahertz photoacoustic effect in the field of non-destructive test and fast real-time imaging is revealed.At the same time,it has certain significance for the selection of detectors,detection methods,Terahertz sources and suitable types of biological tissues in the experimental research of Terahertz photoacoustic imaging.