Physio-anatomical Factors in Cochlear Implant Outcomes

描述(由申请人提供)：由于不同人工耳蜗植入系统的平均性能水平高度相似，并且使用相同设备的患者的结果差异很大，因此假设生理解剖学因素在决定单个人工耳蜗术后的结果中起着重要作用。这项应用的长期目标是确定(1)耳蜗大小和形状、(2)电极插入深度和鳞片鼓室位置以及(3)单个植入受试者测量的神经存活和生理反应等外围因素对同一受试者表现差异的解释程度。高分辨率CT成像可以在很大程度上测量与耳蜗骨解剖和电极放置有关的因素。外周生理反应可以用耳壳内诱发电位(IEP)大体上测量，而没有直接的体内神经存活测量。这个项目将试图通过将IEP测量方法与假设完全神经存活和统一神经特征的参考电解剖-神经计算模型进行比较，来评估生理反应和可变神经存活在个体受试者中的综合影响。然而，电子解剖参考模型将基于每个个体受试者的CT成像所确定的耳蜗骨解剖和电极位置。将使用多元线性回归分析来检查这些因素中的每一个在解释受试者业绩结果差异方面的相对和综合贡献。这个探索性项目的直接目标是构建和验证必要的工具来制定这些措施，然后在3-6个Nucleus和3-6个Clarion植入对象中进行一项小型先导性研究，希望能导致随后的大规模研究。具体地说，这项研究将寻求扩大植入前后高分辨率CT图像的精细空间分辨率，在反投影之前使用先进的预处理技术，然后使用来自身体颞骨的Micro-CT图像的基于形状的内插核进行亚像素图像内插和分割。然后，该精细分辨率的CT图像体素空间将在逐个体素的基础上被转换为基于有限元的电解剖神经模型。在一项初步研究中，将计算特定刺激条件下的电场和IEP响应，并与测量的IEP响应进行比较。

DESCRIPTION (provided by applicant): Because mean performance levels across different cochlear implant systems are highly similar, and large outcome variation is observed across patients with the same device, it is hypothesized that physioanatomical factors play a significant role in determining outcome in individual cochlear implant patients. The long-term objective of this application is to determine how well the peripheral factors of (1) cochlear size and shape, (2) electrode insertion depth and scale tympani position and (3) neural survival and physiological responsiveness as measured in individual implant subjects can account for the performance variation seen across the same subjects. Factors related to cochlear anatomy and electrode placement can largely be measured by high-resolution CT imaging. Peripheral physiological responsiveness can be measured grossly using intracochlear-evoked potentials (IEP), whereas there are no direct in vivo measures of neural survival. This project will seek to estimate the combined influence of physiological responsiveness and variable neural survival in an individual subject by comparing IEP measures against a reference electro-anatomical-neural computational model that assumes full neural survival and uniform neural characteristics. The electro-anatomical reference model will be based however on the cochlear anatomy and electrode placement as determined by CT imaging in each individual subject. Multiple linear regression analysis will be used to examine the relative and combined contributions of each of these factors in accounting for variance in the subject performance outcomes. The immediate objective of this exploratory project is to construct and validate the necessary tools to make these measures and then conduct a small pilot study in 3-6 Nucleus and 3-6 Clarion implant subjects, hopefully leading to a subsequent large-scale study. Specifically, this study will seek to extend the fine spatial resolution of pre- and post-implantation high-resolution CT images using advanced preprocessing techniques before back projection, followed by subvoxel image interpolation and segmentation using shape-based interpolation kernels derived from micro-CT images of cadaveric temporal bones. This fine resolution CT image voxel-space will then be converted on a voxel-by-voxel basis into a finite-element-based electro anatomical neural model. Electrical fields and IEP responses will be computed for specific stimulation conditions and compared with measured IEP responses in a pilot study.