Propagation of Light in Tissue and Imaging

一个光在组织中传播的理论模型，它解释了光的散射和吸收，预测了重新发射的光的表面强度的空间分布。该模型允许重新发射引入的光和由组织固有的或引入组织中的嵌入生色团产生的荧光光。通过测量一系列表面强度分布，可以使用逆分析技术重建组织的三维结构。已经开发了用于捕获表面图像以进行分析的原型仪器。激光扫描系统在感兴趣区域的一系列位置将光引入组织，发射的光通过二向色滤光器光学过滤，并成像到冷却的电荷耦合探测器上。使用这种嵌入在高散射混浊介质中的荧光标记进行测量，重建的理论预测与这些已知位置的实验测量之间产生了很好的一致性。这些技术正在被开发为非侵入性方法，用于诊断Sjorgen综合征的唾液腺病变，并识别乳腺癌的前哨淋巴结以进行活检。通过扩展仪器以捕获光谱的近红外区的图像，并使用新型红外线化合物作为定位于组织内所需位置的探测器，可以识别组织内更深层次的结构。

A theoretical model of light propagation in tissue, which accounts for scattering and absorption of light, predicts the spatial profile of the surface intensity of re-emitted light. The model allows for both re-emission of the introduced light and fluorescent light generated by an embedded chromophore either inherent to or introduced in the tissue. Measurement of a series of surface intensity profiles allows reconstruction of the three-dimensional structure of the tissue using inverse analytical techniques. Prototype instrumentation has been developed to capture surface images for analysis. A laser scanning system introduces light into the tissue at a series of sites in the region of interest and the emitted light optically filtered through a dichroic filter and imaged on to a cooled charge coupled detector. Measurements using this instrumentation of fluorescent markers embedded in a highly scattering turbid medium yielded excellent agreement between the reconstructed theoretical prediction and the experimental measurement of these known sites. The techniques are being developed as non-invasive methods to diagnose diseased salivary glands in Sjorgen's syndrome and to identify sentinel nodes for biopsy in breast cancer. Identification of deeper structures within the tissue is possible by extending the instrumentation to capture images in the near infra-red region of the spectrum and by the use of novel infra-red compounds to act as probes localized at desired sites within the tissue.