Multi-Scale Characterization of Human Internal Organs

The purpose of this paper is to present a multi-scale approach for the biomechanical characterization of the human liver, spleen, lung and heart. A four step study is presented to quantify the injury mechanism, biomechanical response, and rate dependent constitutive model for each tissue. First, the CIREN and NASS databases were examined in order to determine crash characteristics for injuries for each of the four organs. From this step, the injury mechanism relative to loading directions and loading rates could be approximated. Second, whole fresh human organs were tested within 36 hours of death using multiple rates of indenter style tests up to 50% compression. Third, fresh human organs were processed into either dog-bone tension coupons or cylindrical compression coupons and tested at multiple strain rates to the point of failure within 48 hours of death. Fourth, each whole organ and tissue test was recreated using FEM with scanned geometry. An optimization routine was used to develop the best constitutive model for each organ tissue. The full test matrix consists of 860 individual experiments. The overall methodology and preliminary results of the whole body, organ, tissue and modeling are presented. It is anticipated these results will provide the foundation for human FEM tissue properties. INTRODUCTION In a study of the NASS data base from 1988 – 1994 performed by Elhagediab and Rouhanna it was determined the injuries to the chest and abdomen account for 37.6% and 8% of AIS 3+ injuries, 46.3% and 16.5% of AIS 4+ injuries, and 43.3% and 20.5% of AIS 5+ injuries respectively (Elhagediab and Rouhana 1998). Although it was demonstrated that these injuries account for a significant portion of injuries in automotive crashes, there is limited data post 1998 for the epidemiology of injuries in automotive crashes. Finite element models are becoming increasingly useful to understanding these injuries; however, material properties need to be obtained for the models to be accurate and effective. Therefore, the purpose of the study was to use a multi-scale approach to characterize injuries and material properties of the heart, lungs, liver and spleen. This approach consists of four parts: 1) Determine the incidence of injuries in automotive crashes, 2) Perform impacts to intact whole organs, 3) Perform tissue level tension and compression tests, and 4) Develop accurate computational models from the tissue level tests (Figure 1). Material Optimization Tissue Testing Organ Testing Whole Body Data Analysis Tension And Compression Tension And Compression Liver