For a forensic expert-practitioner, it is especially important to objectively diagnose and time since the formation of hemorrhage (TSFH) in the substance of the human brain (SHB) of traumatic and non-traumatic origin, as there are cases when the external examination of the corpse at the scene are absent, and at internal research find hemorrhages in a brain. In forensic practice, to verify the cause of death, physical-optical methods are successfully used, which are based on laser irradiation of biological tissues with subsequent mathematical and statistical processing of the obtained data. Previous studies on the possibility of differentiating the cause of death by traditional polarization methods have yielded positive results, which suggests the possibility of their suitability for verification of the genesis of hemorrhage into the brain. For a forensic expert-practitioner, the main thing is objectivity, accuracy and speed of obtaining the result, which could fully satisfy the methods of laser polarimetry in the case of determining the TSFH of traumatic and non-traumatic origin in SHB. Therefore, it is necessary to continue the development and research of these methods for this purpose.
Aim of the work. To substantiate the possibility of using the method of differential Mueller-matrix mapping of phase anisotropy to determine the temporal dynamics of maps of linear birefringence of histological sections of human brain in determining the age of hemorrhage in human brain substance and to develop forensic criteria for determining the age. death due to cerebral infarction of ischemic and hemorrhagic origin.
Materials and methods. To achieve this goal, we studied native histological preparations SHB from 130 corpses with a known time of death. The cause of death was TBI (group II (n=35)), cerebral infarction of ischemic origin (group III (n=32)), hemorrhagic stroke (group IV (n=33)), acute coronary insufficiency (group I – comparison group (n=30)). The values of the distribution of the coordinates of the polarization parameters at the points of the microscopic images at the location of the standard Stokes polarimeter were measured. Experimental measurements of Stokes-parametric images of biological layers were performed according to the method presented in the sources. Subsequently, the obtained data were subjected to statistical processing and evaluation of the obtained results. Statistical moments (SM) of the 1st-4th orders (mean (SM1), variance (SM2), asymmetry (SM3) and excess (SM4)) of each map were determined.
Results and discussion. Comparative analysis of polarization Mueller-matrix mapping images of SHB sections from all groups revealed the destruction of the polycrystalline structure formed by optically active protein complexes of the brain substance, which indicates a decrease in absolute values and range of their scatter with increasing hemorrhage time. This is indicated by the coordinate inhomogeneity of the Mueller-matrix invariant maps of histological sections of SHB of all groups. For histograms that characterize the distributions of the Mueller-matrix invariant samples from all (comparison groups 1 and experimental 2-4) groups, are characterized by individual and significant variations in the values of statistical moments. Due to this, with increasing hemorrhage time, the value of the mean (SM1) and variance (SM2) decreases. Asymmetry (SM3) and excess (SM4), on the contrary, increase. The analysis of the results of statistical processing of the topographic structure of LD tomograms of fibrillar networks of histological sections of SHB dead from all groups shows a greater temporal dynamics of necrotic destruction of nervous tissue. Accordingly, there is a faster time decrease in the absolute values and the range of scatter of the LD value with increasing TSFH. That is, the diagnostic sensitivity of the statistical moments of the 3rd and 4th orders for azimuthal-invariant Mueller-matrix differentiation of nerve tissue samples of the brain of the deceased of control group 1 and all experimental groups 2-4 (p<0,05) was revealed.
Conclusions. A series of studies of the effectiveness of a new in forensic practice method of differential Mueller-matrix mapping of partially depolarizing histological sections of SHB and tomographic reproduction of optical anisotropy parameters of their polycrystalline structure revealed a high level of accuracy of differentiation and formation of genesis, even under conditions of small geometric thickness of experimental samples. The range of linear change of values of statistical moments of the 1st - 4th orders which characterize distributions of size of LD of fibrillar networks of histologic sections of SHB of the dead from all groups, makes 24 h. In the range of 6-24 hours, the accuracy of determining the TSFH using statistical processing of the topographic structure of LD tomograms of fibrillar networks of histological sections of TSFH is (30±5) minutes.
3D Mueller-matrix mapping of biological optically anisotropic networks