Badachhape Andrew A, Okamoto Ruth J, Johnson Curtis L, Bayly Philip V
Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States.
Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO, United States.
J Biomech. 2018 May 17;73:40-49. doi: 10.1016/j.jbiomech.2018.03.028. Epub 2018 Mar 17.
The objective of this study was to characterize the relationships between motion in the scalp, skull, and brain. In vivo estimates of motion transmission from the skull to the brain may illuminate the mechanics of traumatic brain injury. Because of challenges in directly sensing skull motion, it is useful to know how well motion of soft tissue of the head, i.e., the scalp, can approximate skull motion or predict brain tissue deformation. In this study, motion of the scalp and brain were measured using magnetic resonance elastography (MRE) and separated into components due to rigid-body displacement and dynamic deformation. Displacement estimates in the scalp were calculated using low motion-encoding gradient strength in order to reduce "phase wrapping" (an ambiguity in displacement estimates caused by the 2 π-periodicity of MRE phase contrast). MRE estimates of scalp and brain motion were compared to skull motion estimated from three tri-axial accelerometers. Comparison of the relative amplitudes and phases of harmonic motion in the scalp, skull, and brain of six human subjects indicate that data from scalp-based sensors should be used with caution to estimate skull kinematics, but that fairly consistent relationships exist between scalp, skull, and brain motion. In addition, the measured amplitude and phase relationships of scalp, skull, and brain can be used to evaluate and improve mathematical models of head biomechanics.
本研究的目的是描述头皮、颅骨和大脑运动之间的关系。颅骨向大脑运动传递的体内估计值可能有助于阐明创伤性脑损伤的力学机制。由于直接感知颅骨运动存在挑战，了解头部软组织（即头皮）的运动能多好地近似颅骨运动或预测脑组织变形是很有用的。在本研究中，使用磁共振弹性成像（MRE）测量头皮和大脑的运动，并将其分为刚体位移和动态变形引起的分量。为了减少“相位缠绕”（由MRE相位对比的2π周期性导致的位移估计中的模糊性），使用低运动编码梯度强度计算头皮中的位移估计值。将头皮和大脑运动的MRE估计值与由三个三轴加速度计估计的颅骨运动进行比较。对六名人类受试者头皮、颅骨和大脑中谐波运动的相对振幅和相位的比较表明，基于头皮的传感器数据在估计颅骨运动学时应谨慎使用，但头皮、颅骨和大脑运动之间存在相当一致的关系。此外，测量的头皮、颅骨和大脑的振幅和相位关系可用于评估和改进头部生物力学的数学模型。
