| Bio-tissue optics is the basic of the light diagnostic and therapeutic medicine, whose most critical problem is the measurement of the optical properties of the turbid tissues, such as the absorption a, the scattering s,and the am'sotropy coefficient g. In this paper, the optical properties of ultrashort laser pulse within turbid tissues has been investigated and discussed.As we known that the laser pulse energy will be attenuated in the turbid media and the pulse shape will be changed by scattering and absorption. Besides, the ultra short laser pulse will be widened by the diffusive scattering. The various medium parameters have different influence on the reflection of the laser pulse. Based on the diffusion approximation theory, the boundary condition of semi-infinitehomogeneous media, the influence of the absorption a, the scattering sand the anisotropy coefficient g on the ultra short laser pulse of different pulse-width and shapes has been researched.The background, meaning and the recent advance of measurement of tissue optical properties by time resolved reflectance and transmittance were introduced in the section 1. In the section 2, firstly based on the diffusion approximation theory, the temporal characteristics of the reflectance and the transmittance were theoretically analyzed in turbid tissues; secondly, the curves were simulated that the intensity and the pulse shape of the time resolved reflectance and transmittance versus theabsorption a, the scattering s and the anisotropy coefficient g in twodifferent boundary conditions: semi-infinite turbid media and homogeneous slab; at last, the optical properties can be derived from the curves; In the section 3, the conditions of ultra short laser pulses of different pulse-width and shapes has been theoretical analyzed and calculated, besides, the simulated the curves of the intensity and pulse shapes of the reflectance and transmittance in a homogeneous slab are obtained for use and future studying. |
PDF Full Text Request