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. 2014 Dec 15;6(1):144-54.
doi: 10.1364/BOE.6.000144. eCollection 2015 Jan 1.

Spatial mapping of proteoglycan content in articular cartilage using near-infrared (NIR) spectroscopy

Isaac O Afara  1 , Hayley Moody  2 , Sanjleena Singh  3 , Indira Prasadam  4 , Adekunle Oloyede  2
Affiliations

Spatial mapping of proteoglycan content in articular cartilage using near-infrared (NIR) spectroscopy

Isaac O Afara et al. Biomed Opt Express. .

Abstract

Diagnosis of articular cartilage pathology in the early disease stages using current clinical diagnostic imaging modalities is challenging, particularly because there is often no visible change in the tissue surface and matrix content, such as proteoglycans (PG). In this study, we propose the use of near infrared (NIR) spectroscopy to spatially map PG content in articular cartilage. The relationship between NIR spectra and reference data (PG content) obtained from histology of normal and artificially induced PG-depleted cartilage samples was investigated using principal component (PC) and partial least squares (PLS) regression analyses. Significant correlation was obtained between both data (R(2) = 91.40%, p<0.0001). The resulting correlation was used to predict PG content from spectra acquired from whole joint sample, this was then employed to spatially map this component of cartilage across the intact sample. We conclude that NIR spectroscopy is a feasible tool for evaluating cartilage contents and mapping their distribution across mammalian joint.

Keywords: (170.3880) Medical and biological imaging; (170.6510) Spectroscopy, tissue diagnostics; (170.6935) Tissue characterization.

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Figures

Fig. 1
Fig. 1
Study protocol flow diagram
Fig. 2
Fig. 2
(A) Typical absorbance-depth profiles of safranin-O stained cartilage sections showing proteoglycan loss in cartilage samples, and (B) representative near infrared absorption spectra (offset corrected) for (a) group 0, (b) group 1, (c) group 2, (d) group 3, and (e) group 4.
Fig. 3
Fig. 3
Scores plot of the 1st and 2nd principal components of near infrared (NIR) spectral data showing classification of articular cartilage samples into distinct groups based on their PG content grade. Ellipse shows sub-group within class 2.
Fig. 4
Fig. 4
Partial least squares calibration (a) and validation (b) plots for correlation between near infrared (NIR) spectral data and PG content for normal and artificially degraded cartilage samples. Agreement between AS1 and AS2 grading results (c), and validation of NIR-predicted PG content data against results of AS2 (d).
Fig. 5
Fig. 5
(a) Image of bovine patella with focal defect. (b) Raw (low-resolution) image of PG distribution across sample. (c) Smoothed (bilinear interpolated) image showing distribution of percentage PG loss across sample.
See this image and copyright information in PMC

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