Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
Analyst. 2012 Jan 7;137(1):77-81. doi: 10.1039/c1an15847c. Epub 2011 Nov 4.
Advances in fiber optic probe design are moving Raman spectroscopy into the clinic, although there remain important practical problems. While much effort has been devoted to minimizing Raman and fluorescence background from fibers, less attention has been given to the need to generate reference Raman signals that can correct for variations in tissue albedo, which is important in quantifying changes in tissue composition. To address this shortcoming, we have developed a fiber optic probe that incorporates a fluorinated ethylene-propylene copolymer (FEP) cap at the end of each excitation fiber. Transmission of laser light through the transparent cap generates a 732 cm(-1) Raman band whose intensity scales linearly with the laser power delivered to the tissue of interest. In our first design, the FEP cap functions as a waveguide with only a small insertion loss (~5%). Laser transmission through 1 mm of the polymer is sufficient to generate a usable reference Raman signal. We show the application of the probe to quantitative non-invasive Raman spectroscopy of animal tissues using rat leg phantoms as models. Ex-vivo Raman spectroscopy of excised rat tibia supports the use of the probe for spectroscopy of various tissues. These results provide proof of principle that the Raman probe can be used in multiple spectroscopic applications.
光纤探头设计的进步正在将拉曼光谱技术推向临床应用，但仍存在一些重要的实际问题。虽然已经做了很多努力来最小化光纤的拉曼和荧光背景，但对于产生参考拉曼信号以校正组织反照率变化的需求关注较少，组织反照率变化对于定量组织成分变化很重要。为了解决这一不足，我们开发了一种光纤探头，在每个激发光纤的末端都有一个氟化乙烯丙烯共聚物（FEP）帽。激光通过透明帽传输会产生一个 732cm-1 的拉曼带，其强度与传输到感兴趣组织的激光功率成线性比例。在我们的第一个设计中，FEP 帽作为波导，仅具有较小的插入损耗（~5%）。聚合物中传输 1mm 的激光就足以产生可用的参考拉曼信号。我们展示了该探头在动物组织定量非侵入性拉曼光谱学中的应用，以大鼠腿模型作为模型。离体大鼠胫骨的拉曼光谱支持该探头在各种组织光谱学中的应用。这些结果提供了原理证明，即该拉曼探头可用于多种光谱学应用。
