T2* and quantitative susceptibility mapping in an equine model of post-traumatic osteoarthritis: assessment of mechanical and structural properties of articular cartilage

Abstract

Objective: To investigate the potential of quantitative susceptibility mapping (QSM) and T2* relaxation time mapping to determine mechanical and structural properties of articular cartilage via univariate and multivariate analysis. Methods: Samples were obtained from a cartilage repair study, in which surgically induced full-thickness chondral defects in the stifle joints of seven Shetland ponies caused post-traumatic osteoarthritis (14 samples). Control samples were collected from non-operated joints of three animals (6 samples). Magnetic resonance imaging (MRI) was performed at 9.4 T, using a 3-D multi-echo gradient echo sequence. Biomechanical testing, digital densitometry (DD) and polarized light microscopy (PLM) were utilized as reference methods. To compare MRI parameters with reference parameters (equilibrium and dynamic moduli, proteoglycan content, collagen fiber angle and-anisotropy), depth-wise profiles of MRI parameters were acquired at the biomechanical testing locations. Partial least squares regression (PLSR) and Spearman's rank correlation were utilized in data analysis. Results: PLSR indicated a moderate-to-strong correlation (r ¼ 0.49e0.66) and a moderate correlation (r ¼ 0.41e0.55) between the reference values and T2* relaxation time and QSM profiles, respectively (excluding superficial-only results). PLSR correlations were noticeably higher than direct correlations between bulk MRI and reference parameters. 3-D parametric surface maps revealed spatial variations in the MRI parameters between experimental and control groups. Conclusion: Quantitative parameters from 3-D multi-echo gradient echo MRI can be utilized to predict the properties of articular cartilage. With PLSR, especially the T2* relaxation time profile appeared to correlate with the properties of cartilage. Furthermore, the results suggest that degeneration affects the QSM-contrast in the cartilage. However, this change in contrast is not easy to quantify.

Evaluation of articular cartilage with quantitative MRI in an equine model of post‐traumatic osteoarthritis

“…Prior to MRI, all samples (14 experimental and six control) underwent biomechanical indentation testing of cartilage surrounding the repaired lesions, as described before. 21,22 In short, the samples were submerged in phosphate-buffered saline (PBS) and glued on a custom-made sample holder. First, a plane-ended indenter (d = 0.53 mm) was driven in contact with the sample.…”

A Useful Combination of Quantitative Ultrashort Echo Time MR Imaging and a Probing Device for Biomechanical Evaluation of Articular Cartilage

“…If surgical intervention such as micro-fracture [ 3 ] or cartilage replacement [ 4 , 5 , 6 ] to degenerated or damaged cartilage is necessary, there are the following two potential approaches to know the mechanical property of articular cartridge. In pre-operative and post-operative phases, quantitative magnetic resonance (MR) images is one approach (noninvasive approach) [ 7 , 8 ]. If the quantitative MR images can detect not only lesion area, and they can provide mechanical property of the cartilage tissue, we can match the mechanical property of tissue or material for the cartilage replacement with the mechanical property of marginal area around the lesion.…”

“…Also, relatively new quantitative MR images such as ultrashort echo time (UTE) magnetization transfer (UTE-MT) and UTE-T2* mapping have been reported for diagnosis of early cartilage degeneration [ 12 , 13 , 14 , 15 , 16 ]. However, only a few studies reported on the correlation between quantitative MR images and classical mechanical properties of the articular cartilage [ 7 , 8 ].…”

T2* mapping in an equine articular groove model: Visualizing changes in collagen orientation

“…Another explanation could be that the superficial zones are damaged or partly disappeared, such that the average T2* values within the VOI mostly reflect the middle and deep zone of the cartilage. Several studies have shown a tendency to a decrease in T2* relaxation times from superficial to the deep zone 4,19. Hesper et al7 found that T2* relaxation times were lower in damaged cartilage, as evaluated by arthroscopy.…”