【作者】 赵军；

【导师】 丁海曙； 周丛乐；

【作者基本信息】 清华大学 ， 生物医学工程， 2005， 博士

【摘要】 大脑的神经细胞活动伴随着脑组织光学特性的变化。因此,大脑组织的光学参数可以为我们提供关于大脑生理学和病理学方面丰富的信息。利用近红外光线对人体组织良好的穿透特性可以实现对大脑组织光学参数的无损检测。最近二十多年来,近红外光谱技术在组织光学领域得到了巨大的发展。但是,到目前为止,人类头部的活体组织光学参数,特别是新生儿大脑的光学参数还没有得到深入研究。本文的工作就是紧密围绕着利用频域近红外光谱系统实现对新生儿大脑组织光学参数的无损检测展开的。频域近红外光谱系统利用一个高频正弦信号对光源进行调制,从而在大脑这类强散射介质中形成一种漫射光子密度波。由于组织对光线的吸收和散射作用,距离光源一定距离处的漫射光子密度波的振幅和相位都发生了变化。通过对光子漫射密度波的理论分析,我们提出如果借助一个光学参数已知的校准模型,就可以利用一对固定距离的光源和检测器实现光学参数的无损检测。这种单间距方法相对于传统的频域多点斜率拟合测量方法更加适合于非均匀介质的检测,同时也解放了探头设计中的形状束缚。这些研究结果对于将来频域近红外漫射光成像系统的研制具有指导性作用。论文中完成了一套可用于新生儿头部光学参数无损测量的便携式频域近红外光谱系统的原型机。我们还研制了具有与人体组织相近的光学特性的标准光学参数模型。包括用于实验室测试的配置灵活的Intralipid-Ink 模型和更加便于临床环境的固体硅树脂模型。我们成功地将这套频域近红外系统应用到了临床环境中。通过对44 例新生儿进行初步研究,首次获得了正常新生儿头部光学参数和生理学参数的分布情况和统计结果。更多还原

【Abstract】 Brain activity is associated with changes in optical properties of brain tissue. The measurements of optical properties in brain tissue can provide information on a variety of physiology and pathology processes. The near-infrared light could penetrate more deeply into the thick tissue make it possible to non-invasively determine the optical properties of brain. Near-infrared spectroscopy (NIRS) has been widely used in biomedical optics for more than twenty years. However, the optical properties of the head, especially the neonatal brain are not particularly well known. This work focus on the non-invasive measurements of the optical properties in new-born neonate brains. The frequency-domain NIRS instruments modulate the light with a RF sine wave, which generates diffuse photon density wave (DPDW) in turbid tissue like brain. The amplitude and phase of the DPDW change due to the absorption and scattering of the tissue. We present that the optical properties of tissue could be obtained for a single source-detector separation by comparing the tissue response to a calibration standard. Compared with the multi-distance method, this configuration is more accurate in imaging applications of macroscopically heterogeneous brain. This project involved the development and evaluation of a prototype of portable frequency-domain NIRS which could be used in clinical situations. Two kind of standard phantoms were employed in this project, including the Intralipid-Ink phantoms and solid silicon resin models. We have investigated the optical properties of the brain in forty four neonates in vivo using our frequency domain near-infrared spectroscopy (NIRS). For the first time, the distribution of optical properties and physiological parameters in normal infant brains were demonstrated.更多还原