ABSTRACT
Objective To provide reference indexes and theoretical basis for age estimation of blood pools by investigating the entire drying process and monitoring the change of morphology and mass. Methods Four 15 mL blood pool samples were prepared on the clean ceramic plate. The change of morphology and mass of blood pools in a closed dark environment with a temperature of （20.0±0.5） ℃ and a humidity of 35%-45% were dynamically observed from 0 h to 60 h. Images of the blood pools were recorded by digital camera. The area of blood pools was calculated by MATLAB R2014b, the length of cracks was measured by Image J and the statistical analysis was performed by SPSS 16.0. Results By summarizing and analyzing, the drying of blood pools was divided into five stages： coagulation （0-4.5 h）, gelation （>4.5-20.0 h）, gel-solid mixing （>20.0-37.0 h）, solid （>37.0-40.0 h） and final desiccation （>40.0-45.0 h）. From 0 to 45 h, the mass of the blood pools decreased linearly with time, and the decrease was not obvious from 45.0 to 60.0 h. The standardized mass （y2） showed strong correlation with the time （x） y2=0.018 2 x+0.271 4（R2=0.967 9）. The area change rate of blood pools, the distance that the edge of blood pools moved, the average length of radical cracks had little correlation with the time that passed. Conclusion The overall morphological characteristics of blood pools show a certain regularity with the time and the standardized indexes established provide a reference for the age estimation of blood pools.