T2 relaxation time and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) of human patellar cartilage at 1.5 T and 9.4 T: Relationships with tissue mechanical properties.

Quantitative magnetic resonance imaging (MRI) techniques have been developed for noninvasive assessment of the structure of articular cartilage. T2 relaxation time is sensitive to the integrity and orientation of the collagen network, while T1 relaxation time in presence of Gd-DTPA2- (dGEMRIC) reflects the proteoglycan content of cartilage. In the present study, human patellar cartilage samples were investigated in vitro to determine the ability of MRI parameters to reveal topographical variations and to predict mechanical properties of cartilage at two different field strengths. T2 and dGEMRIC measurements at 1.5 T and 9.4 T were correlated with the static and dynamic compressive moduli at six anatomical locations of the patellar surface. Statistically significant linear correlations were observed between MRI and mechanical parameters at both field strengths, especially between T2 and Young's modulus. No significant difference was found between the T2 measurements at different field strengths in predicting mechanical properties of the tissue. Topographical variation of T2 values at both field strengths was similar to that of Young's moduli. The current results demonstrate the feasibility of quantitative MRI, particularly T2 mapping, to reflect the mechanical properties of human patellar cartilage at both field strengths.