A simplified method of T₁ρ mapping in clinical assessment of knee joint

Purpose: We assessed the clinical utility of our proposed simplified method for TT₁ρ mapping calculations. Materials and Methods: Ten healthy subjects underwent scanning on a 3-tesla magnetic resonance system using an 8-channel phased-array coil. For each subject, we obtained sagittal T₁ρ-prepared images using 5 different time of spin-lock pulses (TSL=1, 20, 40, 60, and 80 ms), produced conventional TT₁ρ maps (cT₁ρ maps) using all TSLs, and recomputed our proposed simplified T1ρ maps (sT₁ρ maps) using a decreasing number of TSLs (from 4 to 2). We then investigated the differences and correlations in T₁ρ values of the tissues obtained using different numbers of spin-lock times. Results: There was a strong positive correlation (single measure intraclass correlation coefficient=0.948; 95z confidence interval=0.911 to 0.970) in T₁ρ values of tissues between the cT₁ρ and sT₁ρ [1, 80] maps. The 2 maps were comparable, though there was a small difference in T₁ρ value between the two. The total scan time to acquire the data from 5 spin-lock times was 16 min 15 s. Similarity of the T₁ρ [1, 80] map with the conventional approach reduced scan time by 60z, to 6min 30 s. Conclusion: The clinical relevance of our proposed simplified method is potentially similar to that of the conventional method, and our method requires a shorter examination time and generally preserves the reliability of the T₁ρ relaxation time of the tissues.