Comparison of T1ρ and T2*Relaxation Mapping in Patients with Different Grades of Disc Degeneration at 3T MR

Background: T1 rho and T2* relaxation times are capable of providing information about early biochemical changes in inter-vertebral disk degeneration (IVDD). The purpose of this study was to assess and compare T1 rho and T2* mapping in IVDD with reference to Pfirrmann grade. Material/Methods: Lumbar sagittal T2-weighted, T1 rho and T2* relaxation MRI were performed at 3.0T in 42 subjects covering discs L1-L2 to L5-S1. All the discs were morphologically assessed according to the Pfirrmann grade. Regions of interest (ROIs) were drawn over the T1 rho and T2* mappings, including nucleus pulposus (NP) and annulus fibrosus (AF). Wilcoxon signed rank test, Kruskal-Wallis test, and Spearman rank correlation were performed. Results: The difference in T1 rho and T2* values between NP and AF were highly significant (P<0.001). The trends of decreasing T1 rho and T2* values of both NP and AF with increasing Pfirrmann grades was significant (P<0.01), particularly between Pfirrmann grade II and III (P<0.001), whereas T2* mapping was additionally able to detect changes in the AF between Pfirrmann grade I and II (P<0.05). Pfirrmann grades were inversely significantly correlated with both T1 rho and T2* values in the NP (r=-0.69, P<0.001; r=-0.56, P<0.001) and AF (r=-0.45, P<0.001; r=-0.26, P<0.001). Conclusions: The process of IVDD can be detected by T1 rho and T2* mapping, particularly at early stage, and both methodologies displayed roughly comparable performance.