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A simplified method of T(1)ρ mapping in clinical assessment of knee joint.

PURPOSE
we assessed the clinical utility of our proposed simplified method for T(1)ρ 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 T(1)ρ-prepared images using 5 different time of spin-lock pulses (TSL=1, 20, 40, 60, and 80 ms), produced conventional T(1)ρ maps (cT(1)ρ maps) using all TSLs, and recomputed our proposed simplified T(1)ρ maps (sT(1)ρ maps) using a decreasing number of TSLs (from 4 to 2). We then investigated the differences and correlations in T(1)ρ 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; 95% confidence interval=0.911 to 0.970) in T(1)ρ values of tissues between the cT(1)ρ and sT(1)ρ [1, 80] maps. The 2 maps were comparable, though there was a small difference in T(1)ρ 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 T(1)ρ [1, 80] map with the conventional approach reduced scan time by 60%, to 6 min 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 T(1)ρ relaxation time of the tissues.