To conclude, the CECT technique was found to be sensitive at detecting changes in cartilage tissue due to increased collagen cross-linking. This is important since increased cross-linking has been proposed to be related to the increased injury susceptibility of tissue.

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This study suggests that dQCTA is in best agreement with dGEMRIC(IV) at 45 min after CT contrast agent injection. dQCTA and dGEMRIC were not related to arthroscopy, probably because the remaining cartilage is analysed in dGEMRIC and dQCTA, whereas in arthroscopy the absence of cartilage defines the grading. The findings indicate the importance to take into account the contrast agent concentration in SF in dQCTA and dGEMRIC(IA).

The results revealed that passive diffusion of Gd-DTPA²⁻ was significantly slower than previously assumed, leading to overestimation of the GAG content at equilibrating times of few hours. Moreover, Gd-DTPA²⁻ distribution was found to depend not only on GAG content, but also on collagen content and diffusion direction. Interestingly, the dGEMRIC technique was found to be most sensitive to cartilage degradation in the early stages of diffusion process, suggesting that full equilibrium between gadopentetate and cartilage may not be required in order to detect cartilage degeneration.

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Objective:Contrast-enhanced computed tomography (CECT) has been introduced for the evaluation of cartilage integrity. Furthermore, CECT enables imaging of the structure and density of subchondral bone. In this laboratory study, we investigate the potential of microCECT to simultaneously image cartilage and subchondral bone for the evaluation of tissue healing.Design:Osteochondral lesions (Ø = 6 mm) were surgically created in equine intercarpal joints (n = 7). After spontaneous healing for 12 months, the horses were sacrificed and osteochondral plugs (Ø = 14 mm), including the repair cartilage and adjacent intact tissue, were harvested. The nonfibrillar and fibrillar moduli and the permeability of cartilage were determined using indentation testing. Contrast agent diffusion into the samples was imaged for 36 hours using high-resolution CT. Results from CECT, mechanical testing, and microscopic analyses were compared and correlated.Results:The contrast agent diffusion coefficient showed a significant (P < 0.05) difference between the repair and adjacent intact tissue. MicroCECT revealed altered (P < 0.05) bone volume fraction, mineral density, and microstructure of subchondral bone at the repair site. The contrast agent diffusion coefficient correlated with the moduli of the nonfibrillar matrix (R = −0.662, P = 0.010), collagen fibril parallelism index (R = −0.588, P = 0.035), and glycosaminoglycan content (R = −0.503, P = 0.067). The repair cartilage was mechanically and structurally different from adjacent intact tissue (P < 0.05).Conclusions:MicroCECT enabled simultaneous quantitative evaluation of subchondral bone and monitoring of cartilage repair, distinguishing quantitatively the repair site from the adjacent intact tissue. As the only technique able to simultaneously image cartilage and determine subchondral bone mineral density and microstructure, CECT has potential clinical value.

, "Infrared microspectroscopic determination of collagen cross-links in articular cartilage," J. Biomed. Opt. 22(3), 035007 (2017), doi: 10.1117/1.JBO.22.3.035007. Abstract. Collagen forms an organized network in articular cartilage to give tensile stiffness to the tissue. Due to its long half-life, collagen is susceptible to cross-links caused by advanced glycation end-products. The current standard method for determination of cross-link concentrations in tissues is the destructive high-performance liquid chromatography (HPLC). The aim of this study was to analyze the cross-link concentrations nondestructively from standard unstained histological articular cartilage sections by using Fourier transform infrared (FTIR) microspectroscopy. Half of the bovine articular cartilage samples (n ¼ 27) were treated with threose to increase the collagen cross-linking while the other half (n ¼ 27) served as a control group. Partial least squares (PLS) regression with variable selection algorithms was used to predict the cross-link concentrations from the measured average FTIR spectra of the samples, and HPLC was used as the reference method for cross-link concentrations. The correlation coefficients between the PLS regression models and the biochemical reference values were r ¼ 0.84 (p < 0.001), r ¼ 0.87 (p < 0.001) and r ¼ 0.92 (p < 0.001) for hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP), and pentosidine (Pent) cross-links, respectively. The study demonstrated that FTIR microspectroscopy is a feasible method for investigating cross-link concentrations in articular cartilage.