Hospital of Shandong University, Jinan, People's Republic of China.
Biomed Eng Online. 2011 Nov 2;10:95. doi: 10.1186/1475-925X-10-95.
Fiber-based optical spectroscopy has been widely used for biomedical applications. However, the effect of probe-sample distance on the collection efficiency has not been well investigated.
In this paper, we presented a theoretical model to maximize the illumination and collection efficiency in designing fiber optic probes for biomedical spectra measurement. This model was in general applicable to probes with single or multiple fibers at an arbitrary incident angle. In order to demonstrate the theory, a fluorescence spectrometer was used to measure the fluorescence of human finger skin at various probe-sample distances. The fluorescence spectrum and the total fluorescence intensity were recorded.
The theoretical results show that for single fiber probes, contact measurement always provides the best results. While for multi-fiber probes, there is an optimal probe distance. When a 400- μm excitation fiber is used to deliver the light to the skin and another six 400- μm fibers surrounding the excitation fiber are used to collect the fluorescence signal, the experimental results show that human finger skin has very strong fluorescence between 475 nm and 700 nm under 450 nm excitation. The fluorescence intensity is heavily dependent on the probe-sample distance and there is an optimal probe distance.
We investigated a number of probe-sample configurations and found that contact measurement could be the primary choice for single-fiber probes, but was very inefficient for multi-fiber probes. There was an optimal probe-sample distance for multi-fiber probes. By carefully choosing the probe-sample distance, the collection efficiency could be enhanced by 5-10 times. Our experiments demonstrated that the experimental results of the probe-sample distance dependence of collection efficiency in multi-fiber probes were in general agreement with our theory.
基于光纤的光谱技术已广泛应用于生物医学领域。然而，探头-样品距离对收集效率的影响尚未得到很好的研究。
本文提出了一种理论模型，用于设计光纤探头以最大化生物医学光谱测量中的照明和收集效率。该模型通常适用于具有任意入射角的单根或多根光纤的探头。为了验证该理论，我们使用荧光光谱仪在不同的探头-样品距离下测量人体手指皮肤的荧光。记录了荧光光谱和总荧光强度。
理论结果表明，对于单光纤探头，接触测量总是提供最佳结果。而对于多光纤探头，存在最佳的探头距离。当使用 400-μm 的激发光纤将光传输到皮肤，并使用另外六根 400-μm 的光纤环绕激发光纤收集荧光信号时，实验结果表明，在 450nm 激发下，人体手指皮肤在 475nm 到 700nm 之间具有很强的荧光。荧光强度强烈依赖于探头-样品距离，存在最佳的探头-样品距离。
我们研究了多种探头-样品配置，发现接触测量可能是单光纤探头的首选，但对于多光纤探头效率非常低。多光纤探头存在最佳的探头-样品距离。通过仔细选择探头-样品距离，可以将收集效率提高 5-10 倍。我们的实验证明，多光纤探头中探头-样品距离对收集效率的影响的实验结果与我们的理论基本一致。
