T2 Versus T2* MRI Mapping in the Knee Articular Cartilage at 1.5 Tesla and 3 Tesla

Recently, several studies have shown that T2 and T2* MRI parametric mapping are sensitive to structural and biochemical changes in the extracellular cartilage matrix. The objective of this study was to assess, compare and correlate quantitative T2 and T2* relaxation time of the knee articular cartilage at 1.5 Tesla (T) and 3 Tesla. Thirty-eight symptomatic patients with knee articular cartilage disease and forty-one asymptomatic volunteers were prospectively included in the study. Knee MRI examination was performed by 3 T and 1.5 T scanner. Multi-Echo Spin-Echo (MESE) and Multi-Echo Gradient Echo (MEGE) sequences were used to determine T2* and T2 maps. T2 and T2* relaxation times values were measured in three Regions Of Itnterest (ROI) on knee articular cartilage using mono-exponential analysis fitting algorithm. There was a significant difference between volunteers and patients for T2 and T2* relaxation times values at 1.5 T and 3 T (p<0.05). The comparison between magnetic fields has shown lower T2 and T2* relaxation times at 3 T compared to 1.5 T. Pearson’s correlation analysis between T2 and T2* at 1.5T revealed a significant positive correlation for volunteers (r=0.245, p = 0.01) and a significant negative correlation for patients (0.016, p = 0.018). At 3T, there was a significant positive correlation between T2 and T2* for volunteers (r=0.076) and patients (r=0.165). The correlation of T2 and T2* between 1.5 T and 3T showed a significant negative correlation (r=-0.087, p = 0.01). T2* mapping may be used for the diagnosis of knee articular cartilage osteoarthritis with the advantage of relatively short scanning time, higher SNR, shorter echo times and the non-effect of the stimulated echo compared to T2 mapping.