Skin Cancer Detection Technology Based On Millimeter-wave Surface Plasmon Polaritons Transmission Line

In recent years,the incidence rate and mortality rate of skin cancer both show a positive growth trend.It is considered to be the most common cancer type in the world,which threatens human life and health seriously.Early detection technology of skin cancer is the key because early detection of skin cancer and then timely treatment can greatly improve the cure rate of skin cancer.Skin cancer detection methods mainly include dermoscopic image diagnosis,physical detection technology and microwave detection technology.Dermoscopic image diagnosis has the low accuracy and high complexity,and the radiation in the detection process can be harmful to human body.Therefore,the former two can not meet the requirements of early skin cancer detection.At present,many microwave detection technologies mainly use millimeter wave probe to detect skin cancer.Normal skin tissue and skin cancer tissue have different water content,which leads to different dielectric properties.Millimeter waves irradiat ing skin tissues with different dielectric properties can produce different reflections,so they can be used for skin cancer detection.However,this millimeter-wave probe can only detect a small part of the area at a time,and large-scale skin detection requires multiple scans,which will take a long time.Therefore,the paper proposes a skin cancer detection technology based on millimeter-wave surface plasmon polariton(SPP)transmission line,which can realize real-time,efficient,safe and non-destructive skin cancer detection.At the same time,combined with near-field sensing imaging technology,it can not only detect the location of skin cancer,but also perform two-dimensional imaging of the shape and size of skin cancer.The main research contents of this paper are as follows:The paper explains the dielectric properties of biological tissues and introduces several models for calculating the dielectric properties of biological tissues.Difference of millimeter wave reflection coefficient between normal skin and cancerous skin is caused by the difference of water content,which is the basic reason that millimeter wave can be used to detect skin cancer.Through the first and second-order Debye model,the complex permittivity and conductivity of normal skin and cancerous skin can be calculated to prepare for the establishment of skin models.The design of microwave SSPP transmission lines with different groove depths and millimeter surface wave SPP transmission line combined with substrate integrated waveguide(SIW)are emphasized.SIW is a planar guided wave structure,but it is cheaper and easier to manufacture.It uses two rows of metal through-hole arrays to replace two walls of rectangular waveguides,which is a good candidate for traditional waveguides.The spoof spp can realize the surface plasmon polariton phenomenon similar to the optical frequency band in terahertz and microwave frequency band,solving the problem that metal behaves like an ideal conductor in frequency band below optics.The dispersion characteristics of SSPP transmission line can be changed by changing the groove depth of SSPP transmission line.SSPP has the advantages of near-field enhancement,sub-wavelength resolution,etc.This slow-wave structure has low-pass characteristics.Combined with SIW,a fast-wave structure with high-pass characteristics,it can be made into a millimeter surface wave SPP transmission line,which can be used to detect the location of skin cancer and achieve high-resolution two-dimensional imaging.According to the characteristics of frequency dispersion of transmission lines,using frequency scanning to collect data is a key to re alize real-time imaging.The paper introduces the 1-D and 2-D near-field scattering systems using transmission lines in detail.When the scatterer is close to the surface of the transmission line or the medium on the surface of the transmission line sudden ly changes,weak local scattering will occur,resulting in a small local perturbation without changing nature of the dominant mode of transmission line.Combining with the mathematical tool,this paper uses compressed sensing(CS)technology to efficiently obtain and reconstruct signals.Then,on the basis of 1-D imaging system,the 2-D local reflection coefficient relationship is derived,and mechanical scanning is carried out in the y-axis direction to establish the 2-D imaging system.Finally,the microwave SSPP transmission line was used for near-field imaging verification,and the influence of the groove depth of the transmission line on the near-field imaging was observed.A skin cancer model is established based on the dielectric properties of the skin tissue.Combined with the millimeter-wave SPP transmission line and near-field imaging technology,the skin cancer model was detected.The experimental results show that this method can realize real-time,efficient,safe and low-cost skin cancer detection.Not only can the position of the skin cancer be accurately detected,but also the shape and size of the very small skin cancer detected can be imaged in two dimensions.The results are intuitive and can be used to detect early skin cancer.