Evaluation of a single-breath-hold radial turbo-spin-echo sequence for T2 mapping of the liver at 3T.

OBJECTIVES

T2 mapping of the liver is a potential diagnostic tool, but conventional techniques are difficult to perform in clinical practice due to long scan time. We aimed to evaluate the accuracy of a prototype radial turbo-spin-echo (rTSE) sequence, optimized for multi-slice T2 mapping in the abdomen during one breath-hold at 3 T.

METHODS

A multi-sample (fat: 0-35%) agarose phantom doped with MnCl and 80 subjects (73 patients undergoing abdomen MR examination and 7 healthy volunteers) were investigated. A radial turbo-spin-echo (rTSE) sequence with and without fat suppression, a Cartesian turbo-spin-echo (Cart-TSE) sequence, and a single-voxel multi-echo STEAM spectroscopy (HISTO) were performed in phantom, and fat-suppressed rTSE and HISTO sequences were performed in in vivo measurements. Two approaches were used to sample T2 values: manually selected circular ROIs and whole liver analysis with Gaussian mixture models (GMM).

RESULTS

The rTSE-T2s values exhibited a strong correlation with Cart-TSE-T2s (R = 0.988) and with HISTO-T2s of water (R = 0.972) in phantom with an offset between rTSE and Cart-TSE maps (mean difference = 3.17 ± 1.18 ms). The application of fat suppression decreased T2 values, and the effect was directly proportional to the amount of fat. Measurements in patients yielded a linear relationship between rTSE- and HISTO-T2s (R = 0.546 and R = 0.580 for ROI and GMM, respectively).

CONCLUSION

The fat-suppressed rTSE sequence allows for fast and accurate determination of T2 values of the liver, and appears to be suitable for further large cohort studies.

KEY POINTS

•Radial turbo-spin-echo T2 mapping performs comparably to Cartesian TSE-T2 mapping, but an offset in values is observed in phantom measurements. •Fat-suppressed radial turbo-spin-echo T2 mapping is consistent with T2 of water as assessed by MRS in phantom measurements. •Fat-suppressed radial turbo-spin-echo sequence allows fast T2 mapping of the liver in a single breath-hold and is correlated with MRS-based T2 of water.