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，并且在使用相同器械的患者中观察到较大的结局差异，因此假设生理解剖因素在决定个体人工耳蜗植入患者的结局方面发挥重要作用。本申请的长期目标是确定（1）耳蜗尺寸和形状，（2）电极插入深度和鼓膜位置，以及（3）在个体植入受试者中测量的神经存活和生理反应性的外周因素在多大程度上可以解释相同受试者中观察到的性能变化。与耳蜗解剖结构和电极放置相关的因素可以通过高分辨率CT成像在很大程度上测量。外周生理反应性可以使用脉络膜内诱发电位（IEP）进行粗略测量，而没有直接的体内神经存活测量。本项目将通过将IEP测量与假设完整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，来估计个体受试者生理反应和可变神经存活的综合影响。然而，电解剖参考模型将基于耳蜗解剖结构和电极放置，如每个个体受试者的CT成像所确定的。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性能结局的方差方面的相对和组合贡献。本探索性项目的近期目标是构建和验证进行这些测量的必要工具，然后在3-6名Nucleus和3-6名Clarion植入物受试者中进行小型试点研究，希望能够导致后续的大规模研究。具体而言，本研究将寻求在反投影之前使用先进的预处理技术扩展植入前和植入后高分辨率CT图像的精细空间分辨率，然后使用来自尸体颞骨微CT图像的基于形状的插值内核进行亚体素图像插值和分割。然后，该精细分辨率CT图像体素空间将逐个体素地转换成基于有限元的电解剖神经模型。将计算特定刺激条件下的电场和IEP反应，并与初步研究中测得的IEP反应进行比较。

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.