Mass properties of the human head are critical elements in developing neck injury threshold criteria in acceleration and impact environments. In order to accurately simulate the dynamics of the head in impact and acceleration environments, valid mass properties data for the human head must exist.
The purpose of this study was two-fold: First, to directly measure and generate a useful data set of human head mass properties and anthropometry, and second, compare the results from the direct measurement to measurements obtained using computed tomographic (CT) analyses of the human head. Four cadaveric human heads, all male, were measured.
For the direct measurement procedure, each frozen specimen was secured in a lightweight-aluminum box. The mass, center of gravity (CG) and principal moments of inertia (MOI) were then measured. These same properties of the box alone were subtracted from the measured quantities to determine each specimen's mass properties. For the CT analysis, the identical specimen preparation was imaged with CT. With both slice collimation and table feed set at 1 mm, the CT image resolution was 0.284 mm3/voxel. Segmentation of tissue types based on density thresholds was used to divide the volumetric data into brain matter, bone, and fat/skin. Surfaces from these groups were extracted to create volumes representing these structures. Assigning mass densities to the segmented volumes, the mass properties of the head were calculated using MIMICS, a 3D ing program and results were compared.
The final results showed the method to be accurate. The average weight for the directly measured heads was 8.96 lb compared to 8.99 lb for the calculated. The average shift in the z-axis (CGz) for the directly measured heads was 0.91 in above the Frankfort origin while the measured shift was 1.00 in on average. Overall, there was no significant difference seen among any of the parameters at α = 0.05.