Estimation of 6 Degrees-of-Freedom Accelerations from Head Impact Telemetry System Outputs for Computational Modeling

To understand the biomechanical basis of head impacts, finite element (FE) modeling is used to estimate the response throughout the brain in various impact conditions. FE simulation of head motion requires a complete description of kinematics, such as six degrees of freedom (6DOF) linear and rotational acceleration curves defining the boundary conditions. These are not available from many common head impact sensors such as the Head Impact Telemetry (HIT) System. At the same time, there are hundreds of thousands of impacts, likely millions of impacts, collected by HITS which represent an underutilized resource for computational modeling. The goal of this study was to develop an algorithm to determine 6DOF acceleration curves based on the corresponding HITS output data for use in FE modeling. The transformation algorithm was developed from a dataset of 14,767 head impacts collected with the HIT System and the corresponding 6DOF information provided by a published algorithm for this study. The impacts were sorted into impact regions and classified by the polarity of peak accelerations, and characteristic curves for each polarity combination were calculated. The algorithm was validated against 50 random impacts by comparing predicted and true acceleration curves using an objective curve comparison metric, CORA, to quantify error. These results demonstrate the algorithm accurately estimates 6DOF motion characteristics from 5DOF inputs sufficient for the purpose of performing basic biomechanical analyses of the impacts through FE modeling.