Two discriminant methods, partial least squares-discriminant analysis (PLS-DA) and Fisher's discriminant analysis (FDA), were combined with Fourier transform infrared imaging (FTIRI) to differentiate healthy and osteoarthritic articular cartilage in a canine model. Osteoarthritic cartilage had been developed for up to two years after the anterior cruciate ligament (ACL) transection in one knee. Cartilage specimens were sectioned into 10 μm thickness for FTIRI. A PLS-DA model was developed after spectral pre-processing. All IR spectra extracted from FTIR images were calculated by PLS-DA with the discriminant accuracy of 90%. Prior to FDA, principal component analysis (PCA) was performed to decompose the IR spectral matrix into informative principal component matrices. Based on the di?erent discriminant mechanism, the discriminant accuracy (96%) of PCA-FDA with high convenience was higher than that of PLSDA. No healthy cartilage sample was mis-assigned by these two methods. The above mentioned suggested that both integrated technologies of FTIRI-PLS-DA and, especially, FTIRI-PCA-FDA could become a promising tool for the discrimination of healthy and osteoarthritic cartilage specimen as well as the diagnosis of cartilage lesion at microscopic level. The results of the study would be helpful for better understanding the pathology of osteoarthritics.

传统的时间调制型傅里叶变换红外成像光谱仪的激光采样通过采用单个激光探测器探测激光干涉强度变化生成采样脉冲,其采样原理简单易实现。但该方法无法判断动镜移动的方向,也难以实现高频采样。对时间调制型傅里叶变换红外成像光谱仪的采样方案进行了对比分析,并针对快扫描采样方法提出了具体的实施方案。从原理和光路设计上介绍了一种适用于时间调制型傅里叶变换红外成像光谱仪的新的采样方法。该方法在传统引入参考激光的基础上,采用偏振的手段将参考激光分为具有固定相位差的两束光,并利用这两束光实现动镜移动方向的判断,以及干涉图样的4倍过采样。从原理上综合考虑了各个光学元件的偏振特性,并将该方法从基于正入射的平面镜推广到斜入射的中空角锥反射镜,扩大了该方法的适用范围,从原理上论证了该方法的可行性。

Fourier transform infrared imaging (FTIRI) was used to examine the depth-dependent content variations of macromolecular components, collagen and proteoglycan (PG), in osteoarthritic and healthy cartilages. Dried 6 μm thick sections of canine knee cartilages were imaged at 6.25 μm pixel-size in FTIRI. By analyzing the infrared (IR) images and spectra, the depth dependence of characteristic band (sugar) intensity of PG show obvious difference between the cartilage sections of (OA) and health. The result confirms that PG content decreases in the osteoarthritic cartilage. However, no clear change occurs to collagen, suggesting that the OA influences little on the collagen content at early stage of OA. This observation will be helpful to further understand PG loss associated with pathological conditions in OA, and demonstrates that FTIRI has the potential to become an important analytical tool to identify early clinical signs of tissue degradation, such as PG loss even collagen disruption.