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

We assessed the clinical utility of our proposed simplified method for T1ρ mapping calculations. 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 T1ρ 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. There was a strong positive correlation (single measure intraclass correlation coefficient=0.948; 95% 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 60%, to 6 min 30 s. 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. (author)