Jansen, S.M.A. (Sanne) (2014) Variation in Optical Coherence Tomography derived Light Attenuation is a Measure for Morphological Differences in Articular Cartilage. thesis, Medicine.
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Abstract
Introduction: It is generally acknowledged that there is a discrepancy between radiographic severity of osteoarthritis (OA) and clinical symptoms. While preventive treatment options are investigated, standard imaging techniques lack in terms of resolution and early disease detection. Optical Coherence Tomography (OCT) is a non-destructive imaging technique utilising the back reflection of near-infrared light to create a cross-sectional image of tissue. The OCT images provide the possibility to measure the light attenuation (μoct), which is a measure for the level of decay of light intensity as a function of image depth, within a certain region of interest. Acknowledging the need for a parameter in determining pathology in OA, μoct could potentially be a quantitative measure to objectify cartilage pathology in OCT images. Materials and Methods: We ex vivo evaluated difference in μoct between healthy cartilage and repair cartilage. In 10 goats osteochondral defects were made in the talus bone of the ankle and after 24 weeks of spontaneously repair the goats were sacrificed for investigation. Light microscopy, polarized light microscopy and OCT images were acquired (Santec IVS-2000). We evaluated 50 OCT scans and 10 histology samples of 10 goats. The μoct measurements were retrieved from different regions of interest (ROI) within the OCT images. Objectifiable structural parameters of histology were obtained using custom-made software. This software calculated the amount of nuclei per area-unit, nucleus size and cellular distribution, thereby highlighting morphological differences in tissue aspects. We focused on the nucleus because previous studies found nuclei as the main scattering objects in tissue. Differences in collagen organisation and structure were observed using polarized light microscopy. Quantification of histology by measurements of custom-made software and difference in morphology observed with polarized light microscopy enhanced our interpretation of the μoct. Results: The mean μoct of cartilage tissue was significantly higher in healthy cartilage (mean 10.10, SD 3.199) compared to repair tissue (mean 3.332, SD 1.439) (p=<0.0001). Also, a trend was observed in which the number of nuclei per area was higher in repair tissue (M 1015, SD 771.7) compared to healthy cartilage (M 532.2, SD 115.9) (p=<0.0084). No difference was found in nucleus size between healthy cartilage and repair tissue. In healthy cartilage, cell positioning was more distant compared to repair tissue. Using the μoct we could objectively determine layers in repair tissue. These layers corresponded with morphological differences in terms of collagen structure and organisation as analysed using polarised light microscopy. Discussion & Conclusion: This study assesses μoct as a quantitative parameter to objectify qualitative OCT images of articular cartilage. OCT in combination with μoct is able to differentiate between healthy cartilage and repair tissue. Light attenuation was able to depict differences in collagen organisation and structure which possibly play a main role in backscattering. Moreover, the combination of OCT and the μoct can clearly determine delicate within-sample variations that remain undetected when using light microscopy alone. " This study is unique because in the measurements for μoct, clearly distinguishable healthy cartilage and repair tissue are taken from the same sample. In addition, we managed to objectify the two different tissues in terms of nucleus count, nucleus size and cellular distribution. These objectifiable differences enabled us to interpret the significant difference in μoct. With polarised light microscopy we were able to determine differences in vessel width and orientation of collagen vessels between healthy cartilage and repair tissue. These findings suggest a main role for collagen in scattering, paving the way for future research.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Stenekes, dr. M.W. |
| Supervisor name: | Strackee, dr. S.D. and Plastische, Reconstructieve en Handchirurgie and Academisch Medisch Centrum, Amsterdam |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 10:57 |
| Last Modified: | 25 Jun 2020 10:57 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/1724 |
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