Propagation of Light in Tissue and Imaging

光在组织中传播的理论模型考虑了光的散射和吸收，预测了再发射光的表面强度的空间分布。该模型允许所引入的光和由嵌入的发色团生成的荧光的再发射，所述发色团是组织固有的或引入组织中的。一系列的表面强度分布的测量允许使用逆分析技术的组织的三维结构的重建。原型仪器已经开发出来，用于捕获表面图像进行分析。激光扫描系统在感兴趣区域中的一系列位点处将光引入组织中，并且所发射的光通过二向色滤光器进行光学过滤并成像到冷却的电荷耦合检测器上。使用这种仪器的测量嵌入在一个高度散射混浊介质的荧光标记物产生了极好的重建的理论预测和这些已知的网站的实验测量之间的协议。该技术正在发展为非侵入性方法，以诊断Sjorgen综合征中患病的唾液腺，并确定乳腺癌活检的前哨淋巴结。通过扩展仪器以捕获光谱的近红外区域中的图像，以及通过使用新型红外化合物作为定位在组织内的期望部位处的探针，可以识别组织内的更深结构。

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.