Whole pancreas water T1 mapping at 3 Tesla.

PURPOSE: A fast T1 mapping method of the whole pancreas remains a challenge, due to the complex anatomy of the organ. In addition, a technique for pancreas water T1 mapping is needed, since the T1 is biased in the presence of fat. The purpose of this work is to accelerate the acquisition of water selective T1 (wT1) mapping for the whole pancreas at 3 T.

METHODS

The proposed method combines a continuous inversion-recovery Look-Locker acquisition with a single-shot gradient echo spiral readout, water-fat separation and dictionary matching for wT1 mapping of the whole pancreas at 3 T. The bias of T1 in the presence of fat was evaluated in a phantom by comparing the modified Look-Locker inversion-recovery (MOLLI) and the proposed method to MRS measurements. The present method was validated in 11 volunteers by evaluating its pancreas coverage and repeatability and by comparing it to MOLLI. Four pancreatitis patients were evaluated using the proposed method and clinical scans.

RESULTS

The phantom wT1 results are in better agreement to MRS ( wT 1 = 1.02 *wT 1 MRS - 47.81 , R 2 = 0.99 ) than MOLLI ( T 1 MOLLI = 1.13 ∗ wT 1 MRS - 74.65 , R 2 = 0.98 ) . The volunteer wT1 results demonstrate the whole pancreas coverage capability for different fat fractions, good repeatability ( wT 1 , 2 ∘ = 0.98 ∗ wT 1 , 1 ∘ + 17.40 , R 2 = 0.69 ) and lower T1 values than MOLLI ( wT 1 = 0.34 *T 1 MOLLI + 383.65 , R 2 = 0.26 ) . The wT1 maps in patients captured diverse pancreatitis regions with higher values ( wT 1 Patients = 831 - 1696 ms ) than in the volunteers wT 1 Volunteers = 605 - 799 ms , thus showing their potential clinical feasibility.

CONCLUSION

The present work proposes a wT1 mapping methodology of the whole pancreas at 3 T, where 24 slices ( 2 × 2 × 5 mm 3 ) were acquired in three short breath-holds of 12 s each.