3-D Measurements of Acceleration-Induced Brain Deformation via Harmonic Phase Analysis and Finite-Element Models

Abstract

<italic>Objective:</italic> To obtain dense spatiotemporal measurements of brain deformation from two distinct but complementary head motion experiments: linear and rotational accelerations. <italic>Methods:</italic> This study introduces a strategy for integrating harmonic phase analysis of tagged magnetic resonance imaging (MRI) and finite-element models to extract mechanically representative deformation measurements. The method was calibrated using simulated as well as experimental data, demonstrated in a phantom including data with image artifacts, and used to measure brain deformation in human volunteers undergoing rotational and linear acceleration. <italic>Results:</italic> Evaluation methods yielded a displacement error of 1.1 mm compared to human observers and strain errors between <inline-formula><tex-math notation= LaTeX >${\\text{0.1}}\\pm {\\text{0.2}}{\\% \\,(\\text{mean}\\pm \\text{std}.\\,\\text{dev.)}}$</tex-math></inline-formula> for linear acceleration and <inline-formula><tex-math notation= LaTeX >${\\text{0.7}}\\pm {\\text{0.3}}\\% $</tex-math></inline-formula> for rotational acceleration. This study also demonstrates an approach that can reduce error by 86% in the presence of corrupted data. Analysis of results shows consistency with 2-D motion estimation, agreement with external sensors, and the expected physical behavior of the brain. <italic>Conclusion:</italic> Mechanical regularization is useful for obtaining dense spatiotemporal measurements of <italic>in vivo</italic> brain deformation under different loading regimes. <italic>Significance:</italic> The measurements suggest that the brain s 3-D response to mild accelerations includes distinct patterns observable using practical MRI resolutions. This type of measurement can provide validation data for computer models for the study of traumatic brain injury.