Mild Brain Injury Predictors Derived From Dummy 6DOF Motions

BRIC (BRain Injury Criterion) and RIC (Rotational Injury Criterion) have been proposed as Mild Traumatic Brain Injury (MTBI) predictors. Both predictors had been verified with football players' head impact data. This study employed two human brain Finite Element (FE) models of THUMS ver.3 and SIMon ver.4 to find out correlations between the MTBI predictors and FE-based brain injury predictors such as Cumulative Strain Damage Measure (CSDM). The CSDM is defined as the percent volume of the brain FE model that exceeds a specified first principal strain threshold, which is proposed to predict Diffuse Axonal Injury (DAI) as one of Traumatic Brain Injury. Four vehicular crash test data obtained from NHTSA database of “Query Vehicle Crash Test Database on select test parameters” were applied to calculate MTBI predictors and the FEbased brain injury predictors. Very small number of crash test data demonstrated that the RIC showed strong correlations with CSDMs predicted by the two human brain FE models. Since BRIC and RIC are different in definitions of brain injury mechanisms, further studies are needed to investigate brain injury mechanisms from the medical point of view and verify the effectiveness of the MTBI predictors using more crash test data. INTRODUCTION IC (Head Injury Criterion) is an effective criterion for head injuries correlated with linear acceleration, such as skull fractures. However, no injury criterion involving head rotational kinematics is fully accepted as effective so far. Recently, BRIC (BRain Injury Criterion) and RIC (Rotational Injury Criterion) have been proposed by Takhounts et al. (2011), and Kimpara and Iwamoto (2012) as MTBI (Mild Traumatic Brain Injury) predictors, respectively. The BRIC is calculated from a summation of normalized maximum angular acceleration and normalized maximum angular velocity. The RIC is defined by H integrating angular acceleration during a pre-determined time duration. Since both predictors stand on the rotational kinematics of the head, it is not clear how comparable or different are the MTBI predictors. In previous study, we evaluated the predictive capabilities of the RIC using only football players' head impact data and a human brain Finite Element (FE) model that we developed previously. However, it is not guaranteed whether the RIC is still effective for severe head impacts during automotive crashes and whether it is still effective for other human brain FE models due to differences in their geometry, material properties, and boundary conditions. In this study, we employed another brain FE model in addition to the brain FE model we used previously, and applied a series of vehicular crash test data to correlation analyses between the two promising MTBI predictors and outcomes from the brain FE models in order to investigate the effectiveness of the MTBI predictors in severe head impacts. METHODS The purpose of this study is to investigate the effectiveness of two MTBI predictors for football player's head impact data and vehicular crash test data by correlation analyses between the MTBI predictors and outcomes from two human brain FE models. This section describes definitions of the two MTBI predictors and characteristic features of the two human brain FE models as well as two types of head impact data and procedure of correlation analyses. MTBI predictors The BRIC is defined as below: cr cr BRIC α α ω ω max max + = (1) where ωmax and αmax are the maximum angular velocity and the maximum angular acceleration for each test, and ωcr and αcr are critical values of angular velocity and angular acceleration, respectively. The critical values are determined as BRIC is equal to 1.0 at 30% probability of DAI with AIS 4+. The equation of RIC is defined as below: ( ) ( ) ( ) RIC t t C t t dt t t t RIC