Imaging of biological structures with pre-fractal properties using
spatial speckle-correlometry technique
D.A. Zimnyakov 
, A.A. Mishin 
, K.V. Larin , V.V. Tuchin
Department of Physics, Saratov State University, Russia (1);
Blagonravov Mechanical Engineering Institute (Russian Academy of Sciences) (2)
Application of the speckle optics methods for scattering biotissues imaging is now one of the prospective directions in optical tomography [1]. For media with high turbidity caused by multiple scattering in tissue volume structure imaging and monitoring can be successfully carried out using correlation analysis of scattered light intensity fluctuations (so-called "time-domain" approach [2]). In the case of relatively weak scattering tissues usage of the focused illuminating beams leads to the formation of partially developed speckle patterns in the far diffraction zone. Analysis of the correlation properties of such dynamic speckles produced by probe beam scanning of the tissue under study can be used for reconstruction of the scattering structures images. Exponential factor of intensity fluctuations of the far-zone speckles can be proposed as visualization parameter, its value characterizes the asymptotic behavior of the boundary field amplitude fluctuations and is directly connected with spatial and correlation properties of the transmittance coefficient distribution for the sample under study. Structure imaging method using moving block data processing algorithm for the calculation of the exponential factor local values has been developed for 2D-reconstruction of the scattering structure images of tissue thin layers. Experiments carried out with the human epidermis samples have shown high sensitivity of such imaging technique to the changes of skin cellular structure caused by various diseases (psoriasis, e. g.) [3]. For the certain regions of spatial scales speckle intensity fluctuations demonstrate the high-frequency peculiarities which can be interpreted as the manifestation of "pre-fractal" behavior of the tissue scattering structure. As it seems, this technique can be proposed as prospective method of the rapid and objective tissue structure monitoring (including specially prepared replicas).