Assessment of mass properties of human head using various three-dimensional imaging modalities.

Better methods are needed to analyse personal protective devices, such as helmets or facemasks, before they are used in practice. Software tools to quantify three-dimensional craniofacial mass properties are developed to improve our understanding of craniofacial impact biomechanics, supplement existing knowledge of osseous structure and provide a comprehensive description of human head morphology. The application of state-of-the-art imaging systems, solid modelling and other software tools are studied to determine the associated errors in mass property estimation by spiral computed tomography, three-dimensional magnetic resonance and optical surface scanning using phantoms and cadaver head studies. Volume, centre of gravity and principal moments of inertia are determined from solid mathematical models for each scanning modality. Landmark-based registration is used to register scans of the same object obtained from the three imaging modalities to a common reference co-ordinate system. Physically and analytically determined mass properties are used as the standard for truth. Although this comparative study does not lend itself to statistical analysis owing to the small sample size, results indicate that any of the three imaging modalities can be used to predict mass properties within the uncertainty of existing methods. Applying these techniques in vivo is practical and feasible.