MRI rotating frame relaxation measurements for articular cartilage assessment

In the present work we introduced two MRI rotating frame relaxation methods, namely adiabatic T-1 rho and Relaxation Along a Fictitious Field (RAFF), along with an inversion-prepared Magnetization Transfer (MT) protocol for assessment of articular cartilage. Given the inherent sensitivity of rotating frame relaxation methods to slow molecular motions that are relevant in cartilage, we hypothesized that adiabatic T-1 rho and RAFF would have higher sensitivity to articular cartilage degradation as compared to laboratory frame T-2 and MT. To test this hypothesis, a proteoglycan depletion model was used. Relaxation time measurements were performed at 0 and 48 h in 10 bovine patellar specimens, 5 of which were treated with trypsin and 5 untreated controls were stored under identical conditions in isotonic saline for 48 h. Relaxation times measured at 48 h were longer than those measured at 0 h in both groups. The changes in T-2 and MT relaxation times after 48 h were approximately 3 times larger in the trypsin treated specimens as compared to the untreated group, whereas increases of adiabatic T-1 rho and RAFF were 4 to 5 fold larger. Overall, these findings demonstrate a higher sensitivity of adiabatic T-1 rho and RAFF to the trypsin-induced changes in bovine patellar cartilage as compared to the commonly used T-2 and MT. Since adiabatic T-1 rho and RAFF are advantageous for human applications as compared to standard continuous-wave T-1 rho methods, adiabatic T-1 rho and RAFF are promising tools for assessing cartilage degradation in clinical settings. (C) 2013 Elsevier Inc. All rights reserved.