DIAGNOSIS OF THE TIME SINCE DEATH BY USING OF THE AZIMUTH-INVARIANT MULLER-MATRIX MICROSCOPY METHOD OF THE HUMAN VITREOUS BODY

Буковинський медичний вісник. Т.24, No 1 (93). С. 128-133.

Introduction. In recent years, the advances in medical science clearly show the desire of scientists to objectify the results in the study of biological tissues and physical mediums of the body that are being analyzed [11,15]. This is a general trend in evidence-based medicine that uses various instrumental diagnostic methods to specify the extent of pathological changes detected in the study [7][8][9]. The state of scientific research in forensic medicine, which tends to use biophysical methods of diagnosis, is no exception [1][2][3][4][5][6]. This is due to the fact that they provide a quantitative objectivity, instead of a subjective evaluation by a medical expert. Biophysical techniques also provide rapid results, allowing them to be used as express diagnostics. In this research, we propose to consider the possibility of laser polarization techniques for the investigation of biological tissues and fluids of the human body for use in forensic practice, in particular for the establishment of time since death (ТSD), because this problem is one of the most relevant for the practitioner expert.
The purpose of the work. To develop a set of new forensic objective criteria to extend the functionality of accurate ТSD detection according to azimuth-invariant Muller-matrix mapping of the coordinate distributions of the Muller phase matrix invariant of the structure of human vitreous body (VB).
Material and methods of research. The VB was collected at the department of the MMI "Regional Bureau of Forensic Expertise" of the Department of Health of Chernivtsi Regional State Administration under mixed lighting, air temperature +18-22 °C and relative humidity of 60-75%. Sampling was performed with an insulin syringe (needle was inserted in the area of the outer corner of the eye) in the amount of 0.25 ml in people who died of cardiovascular pathology with a known time of death (n=76) at different intervals.
Measurements of the magnitudes of the phase distribution of the Muller matrix invariant (MMI) of VB preparations were carried out with a classical Stokes polarimeter, the optical scheme of which is shown in Fig. 1 [12][13][14].
The results of azimuthal-invariant mapping of the coordinate distributions of the phase MMI value illustrate the differences between the optical anisotropy of the fibrillar collagen networks of the layers of the human VB with different TSD. It is found that the coordinate distributions of the phase MMI value of the sample of the VB at TSD 12 hours are characterized by a larger average value and a range of random values compared to the similar coordinate distributions of phase MMI determined for the VB at TSD for 3 hours.
The established fact can be explained by the value of the optical anisotropy, which is inversely proportional to the phase modulation at the points of the plane of the layer of VB [6][7][8][9][10]. Therefore, with the increase of TSD due to necrotic changes, the level of optical anisotropy decreases. Accordingly, the depth of phase modulation of laser radiation is increased by optically anisotropic structures of the VB sample. This necrotic process is accompanied by larger random values of phase MMI [3,4].
The results of the statistical analysis of the temporal dynamics of necrotic changes of the phase MMI maps of the VB layers at different TSD are accompanied by opposite tendencies -the increase of the mean and the variance (Fig. 2). On the contrary, the magnitudes of the statistical moments of the 3rd and 4th orders, which characterize the asymmetry and excess, decrease.
Quantitatively, this scenario of changing the phase structure of fibrillar networks of samples of human VB with different TSD illustrates the statistical moments of the 1st -4th orders, which are shown in table 1.
We found that the linear range of change in the magnitude of the statistical moments of the 1-4th order, which characterize the coordinate distributions of the phase MMI of the layers of the human VB by the TSD is 24 h. The value of SM1 varies within the range defined for all sample groups by the average values from 0.49 to 0.19, SM2 from 0.27 to 0.09, SM3 from 0.51 to 0.97, SM4 from 0.61 to 1.19.  From the obtained data (Fig. 3) it is evident that the values of the mean, variance, asymmetry and excesses linearly change within 24 hours. In this case, the most sensitive to necrotic changes in the polycrystalline structure of the VB were the temporal changes of the asymmetry SM3 and excess SM4. Quantitatively, this is manifested in the increase of the slope angles of such linear dependencies of higher order statistical moments - Table 2.
Analysis of the obtained data on the time dependences of the set of statistical moments of 1-4th orders, which characterize the distribution of magnitude of phase MMI at different intervals of the TSD, revealed the maximum level (highlighted in gray) of accuracy in the determination of the TSD within 44 min. -46 minutes.

Conclusions
1. The method of azimuthal-invariant Muller-matrix mapping of coordinate distributions of phase MMI of layers of human VB with different TSD was tested.
2. The time dynamics of the change in the magnitude of the statistical moments of the 1st -4th orders, which characterize the distribution of the phase MMI of the layers of the human VB with different TSD, is investigated. The range of sensitivity (24 h) and accuracy (44-46 min) of the Muller-matrix mapping method of VB layers into determined TSD were established 3. In order to increase the range of sensitivity and to improve the accuracy of the Muller-matrix mapping method of VB layers, in our opinion, it will be promising to use the information capabilities of the scale-selective wavelet analysis of the coordinate distributions of the phase MMI.