Assessment of knee cartilage strain using the magnetization transfer ratio and T2: an ex vivo study at 9.4T MRI

The magnetization transfer ratio (MTR) was investigated as an alternative biomarker for cartilage strain compared to T2. Six ex vivo bovine knee specimens were compressed in a 9.4T scanner and scanned at several physiological step loads. Average strain, MTR, and T2 were calculated for each voxel column throughout the full depth of cartilage, and depth-dependent trends were identified. ΔMTR changed uniformly across the cartilage volume with strain, while ΔT2 showed a more localized yet inconsistent response. This suggests that MTR may be more sensitive in measuring cartilage strain in clinical applications where image resolution is lower.