Simulation Study on Spectral Characteristics of Skin Tissue and Volume Pulse Wave in 400～1 000 nm Wavelength
ZHOU Liang1, YU Jiang-jun1, 2, LIU Zhao-hui1, LI Zhi-guo1, SHAN Qiu-sha1
1. Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710119, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：According to the anatomical structure of the skin tissue, we established a six-layer model, and the characteristic parameters of each layer of skin tissue were given. We considered the absorption characteristics of oxidized hemoglobin and reduced hemoglobin, and gave the spectral absorption coefficients of each layer of skin tissue according to the contents of water, blood, fat and oxygen saturation in each layer of skin tissue, as well as the size of blood vessels. The scattering coefficients at different wavelengths were simplified properly, and then the scattering coefficient spectra of each layer of skin tissue were obtained. In this paper, we used Monte Carlo method to simulate the transmission process of 400～1 000 nm wavelength light in the multi-layer model of skin tissue under the conditions of contraction and relaxation. The spectral reflectance of the skin tissue was obtained by counting the distribution characteristics of a large number of photons. The amplitude spectrum of volume pulse wave was obtained by calculating the reflection coefficient of the two states obtained from the simulation. The simulation results showed that the volume pulse wave amplitude of green light is better than that of red light and blue light when the incident light intensity is constant. The penetration depth spectrum of skin tissue was obtained by calculating the corresponding skin tissue depth when the light flux of different wavelengths decreased to 1/e along the direction of skin tissue depth. The results showed that the penetration depth of blue light and green light is small, the blue light can only reach the surface layer, the green light can reach the micro-circulation layer, and the penetration depth of red light is the largest, which can reach the dermis directly. Considering when the light travels through the skin, it involves a dynamic process from contraction to relaxation, so we define the depth of pulse signal generation based on penetration depth, and the spectral generation depth is calculated by using the penetration depth of vasodilation and contraction in two different states. The results showed that the depth of light generation at different wavelengths is greater than the penetration depth, the depth of blue light is shallowand the blood absorption modulation is small, so the pulse signal obtained is more easily interfered by noise. The volume pulse wave of red light is deeper than that of green light, but compared with green light, its absorption and modulation by blood is smaller, and the depth of green light generation is enough to reach the dermis vascular layer, so the amplitude of red light volume pulse wave is smaller than that of green light. Our simulation results confirm some spectral characteristics of skin tissue, which provides a theoretical basis for the accurate acquisition of multispectral volume pulse waves and other related studies.
[1] Rajaguru H, Prabhakar S K. Advanced Science Letters, 2015, 21(12): 3602.
[2] Kumar M, Veeraraghavan A, Sabharwa A. Biomedical Optics Express, 2015, 6(5): 1565.
[3] Sun Y, Thakor N. IEEE Transactions on Biomedical Engineering, 2016, 63(3): 463.
[4] Bashkatov A N, Genina E A, Kochubey V I, et al. Journal of Physics D: Applied Physics, 2005，38(15): 2543.
[5] Welch A J, van Gemert M J C. Optical-Thermal Response of Laser-Irradiated Tissue, 2nd ed. American Institute of Mathematical Sciences, 2011: 109.
[6] Li Wei, Lin Ling, Bao Lei, et al. Optical and Quantum Electronics, 2015, 47(7): 1919.
[7] Zhu Caigang, Liu Quan. Journal of Biomedical Optics，2013, 18(5): 050902.
[8] Meglinski I V, Matcher S J. Computer Methods and Programs in Biomedicine, 2003, 70(2): 179.
[9] Tuchin V V. Proc SPIE, 2011, 7898: 78980Z.
[10] Bjorgan A, Milanic M, Randeberg L L, et al. Journal of Biomedical Optics, 2014, 19(6): 066003.
[11] Salomatina E, Jiang B, Novak J, et al. Journal of Biomedical Optics, 2006, 11(6), 064026.
[12] Verkruysse W, Lucassen G W, Boer J F, et al. Physics in Medicine and Biology, 1997, 42(1): 51.
[13] Bosschaart N, Edelman G J, Aalders M C G, et al. Laser in Medical Science, 2014, 29(2)：453.
[14] Yudovsky D, Pilon L. Journal of Biophotonics, 2011, 4(5): 305.
[15] Kong L Q, Zhao Y J, Dong L Q, et al. Optics Express, 2013, 21(15): 17464.
