Abstract
In this study, neutron radiography (NR) is used non-destructively to measure changes in hydrogen (H) content in decaying tissues as a mean to estimate post-mortem invertal (PMI). After death, tissue undergoes sequential changes consisting of organic and inorganic phase variations, as well as a gradual reduction of tissue water content. H is the primary contributor to NR contrast in biological specimens because (1) it is the most abundant element in biological tissues and (2) its nucleus scatter thermal and cold neutrons more strongly than any other atomic nucleus. These contrast differences can be advantageous in a forensic context to determine small changes in hydrogen concentrations. Dog cadavers were used as a model for human cadavers. Canine tissues and cadavers were exposed to controlled (laboratory settings) and uncontrolled (University of Tennessee Anthropology Research Facility) environmental conditions during putefraction, respectively. Neutron radiographs were supplemented with photographs and histology data to assess the decomposition stage of cadavers. Results demonstrated that the increase in neutron transmission likely corresponded to a decrease in hydrogen content in the tissue, which was correlated with the time of decay of the tissue. Tissues depleted in hydrogen are brighter in the neutron transmission radiographs of skeletal muscles, lung, and bone, under controlled conditions. Over a period of 10 days, changes in neutron transmission through lung and muscle were found to be higher than bone by 8.3%, 7.0 %, and 2.0 %, respectively. Estimation of the PMI was calculated from a natural logarithmic fitting of the NR data. Under controlled conditions, estimation of the PMI was 70% and 63.9 % accurate for bone and lung tissues, while being 1.4% accurate for muscle tissue. All results underestimated the true PMI. In conclusion, neutron radiography can be used for detection of hydrogen changes in decaying tissues to estimate PMI.
