Biomechanical Tolerance Criterion for the Spinal Cord

急性脊髓损伤（SCI）始于机械损伤，称为原发性损伤，随后是扩展的生物反应，称为继发性损伤。近十年来的研究进展表明，在动物模型中，原发损伤的特征（如加载速率、方向）对脊髓损伤的模式和严重程度有深远的影响。这些损伤的计算机模拟强调了这些机械作用对组织损伤的重要性。这些模拟具有很大的潜力，可以作为预防伤害的设备和环境（例如头盔和汽车内饰）的设计工具。不幸的是，这些计算机模型作为预测工具存在局限性。需要改进的主要领域包括脊髓组织建模（例如灰质与白质、各向异性）和组织损伤的机械反应（即确定适当的容错标准）。******这项发现资助计划的总体目标是确定更好的脊髓组织耐受性标准。具体目的是确定：1)脊髓灰质和白质的准静态材料特性；2)脊髓灰质和白质的相对各向异性；3)力学标准(如：max。主应变)与脊髓组织损伤最相关。拟议的研究是我目前NSERC发现基金的自然进展。******为了解决这些特定的目标，将进行计算建模，体内实验和磁共振（MR）成像。在实验1和2中，相关的脊髓损伤将在大鼠体内产生，使用定制的MR内脊髓损伤装置和获得的畸形脊髓的MR图像。图像分析将使脊髓应变模式估计成为可能。逆有限元（FE）方法将用于确定灰质和白质的相对材料性能。对于3号工程，将生产三种类型的sci，并使用有限元模型来预测几种可能的公差标准的损伤模式。******这个研究项目在国际标准上是非常新颖的。我们在使用体内模型解决生物力学变量方面处于领先地位，并且是唯一能够在MR扫描仪孔内生产sci的团队。我们对这些损伤进行计算建模的能力已经得到了很好的发展，这是本研究的重要组成部分。这项研究将促进我们对脊髓组织材料特性的理解，从而提高我们预测组织损伤的计算模型的质量。由于脊髓是中枢神经系统损伤的一个很好的模型系统，这些结果很可能转化为脑损伤。这将有助于设计环境（例如在车内）以预防脊柱和脊髓损伤。我们有一个丰富的、跨学科的HQP培训环境，我们希望在这个时间框架内培养两名硕士生和两名博士生。

Acute spinal cord injury (SCI) begins with a mechanical insult, termed primary injury, followed by an extended biological response, called secondary injury. Research advances over the past decade show, in animal models, that features of the primary injury (e.g. loading rate, direction) have profound influences on the pattern and severity of SCI. Computer simulations of these injuries emphasized the importance of these mechanical effects on tissue damage. These simulations have great potential as design tools for devices and environments for injury prevention (e.g. helmets and automobile interiors). Unfortunately, there exist limitations with these computer models as predictive tools. The main areas for improvement include spinal cord tissue modelling (e.g. grey vs. white matter, anisotropy) and relating the mechanical response to tissue damage (i.e. identifying an appropriate tolerance criterion).******The overall goal of this Discovery Grant program is to determine better tolerance criteria for spinal cord tissue. The specific objectives are to determine the: 1) quasi-static material properties of spinal cord grey and white matter; 2) relative anisotropy of spinal cord grey and white matter; and 3) mechanical criteria (e.g. max. principal strain) that best correlate with spinal cord tissue damage. The proposed research is a natural progression of my current NSERC Discovery Grant. ******To address these specific objectives, computational modelling, in vivo experiments, and magnetic resonance (MR) imaging will be conducted. For Obj. 1 and 2, relevant SCIs will be produced in vivo in rats using a custom intra-MR SCI device and MR images obtained of the deformed spinal cords. Image analysis will enable strain pattern estimation in the cord. Inverse finite element (FE) approaches will be used to determine the relative material properties of the grey and white matter. For Obj 3, three types of SCIs will be produced and the FE model used to predict damage patterns with several possible tolerance criteria.******This research program is highly novel by international standards. We are leaders in addressing the biomechanical variables using an in vivo model, and the only group able to produce SCIs inside the bore of an MR scanner. Our ability to computationally model these injuries is well developed and an important component of this proposed research. This research will advance our understanding of the material properties of spinal cord tissue and thus will enhance the quality of our computational models in predicting tissue damage. As the spinal cord is a good model system for injury to central nervous system tissue, these results are likely translatable to brain injury. This will aid the design of environments (e.g. inside of a car) for the prevention of spine and spinal cord injuries. We have a rich, interdisciplinary training environment for HQP and we expect to train two MASc and two PhD students in this timeframe.