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首页> 外文学位 >Determining the optical properties of the human brain using a two-layer diffusion model for non-invasive, frequency domain optical measurements.
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Determining the optical properties of the human brain using a two-layer diffusion model for non-invasive, frequency domain optical measurements.

机译：使用两层扩散模型进行无创频域光学测量，确定人脑的光学特性。

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摘要

The concentrations of oxyhemoglobin [HbO] and deoxyhemoglobin [Hb] in tissue and their temporal dynamics are an important indicator of cognitive function in the brain. Near-infrared (NIR) techniques have been employed to extract the concentration levels of these tissue chromophores due to their non-invasive feature. An integral part of this extraction procedure is a model of light propagation in turbid medium such as human tissue. In this study, we apply the diffusion model since the nature of light-tissue interaction for tissues probed with near-infrared light is highly scatter-dominated. In such a model of light propagation, the quantities of interest are the absorption μ a and the scattering coefficient μs. From the absorption coefficients, the chromophore concentrations can be determined through their molar extinction coefficients. However, the model assumes a homogeneous issue structure and inevitably presents a limitation in the extraction process.;In this study, a two-layer model of the head is proposed to account for the heterogeneity in the tissue architecture of the head in recovering the absorption and reduced scattering coefficients (optical properties) of the brain. The model assumes a superficial layer of finite thickness (first layer) situated over a semi-infinite homogeneous structure (second layer). Applied to the head, the scalp and the skin are lumped together in the first layer and the brain comprises the latter. Values of intensity amplitude (AC) and phase (&thetas;) are acquired in the frequency domain at multiple source-detector distances in a reflectance geometry. The optical properties are then recovered by performing a nonlinear regression to Monte Carlo-generated data for the AC and phase of the detected light. It is shown that the recovered optical properties using this two-layer model exhibits better agreement with the simulations than those recovered from a homogeneous model.;The study hopes to provide an added avenue of refinement to a recent protocol that was developed to perform absolute measurements of cerebral hemoglobin concentration.
机译：组织中的氧合血红蛋白[HbO]和脱氧血红蛋白[Hb]的浓度及其时间动态是大脑认知功能的重要指标。由于其无创性特征，近红外（NIR）技术已被用于提取这些组织发色团的浓度水平。此提取过程不可或缺的一部分是光在浑浊介质（例如人体组织）中传播的模型。在这项研究中，我们应用扩散模型，因为用近红外光探测的组织的光组织相互作用的本质是高度散射主导的。在这种光传播模型中，感兴趣的量是吸收率μa和散射系数μs。根据吸收系数，可通过其消光系数确定生色团浓度。然而，该模型假设均一的问题结构，并且不可避免地在提取过程中存在局限性。;在这项研究中，提出了一个两层的头部模型，以说明头部组织结构在恢复吸收中的异质性并降低了大脑的散射系数（光学特性）。该模型假定位于半无限均质结构（第二层）上的有限厚度的表层（第一层）。涂在头上的头皮和皮肤在第一层集中在一起，而大脑由后者组成。在反射几何结构中，在多个源检测器距离处，在频域中获取强度振幅（AC）和相位（θ）的值。然后，通过对Monte Carlo生成的AC和检测到的光的相位数据进行非线性回归来恢复光学特性。结果表明，使用该两层模型恢复的光学特性与模拟结果相比，从均匀模型中恢复的光学特性表现出更好的一致性。;该研究希望为最近开发的用于进行绝对测量的方案提供精炼的新途径脑血红蛋白浓度。

著录项

  • 作者

    Pillas, Elleesse Carlisle Navarro.;

  • 作者单位

    Tufts University.;

  • 授予单位 Tufts University.;
  • 学科 Engineering Biomedical.
  • 学位 M.S.
  • 年度 2012
  • 页码 78 p.
  • 总页数 78
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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