Snapshot whole-brain T relaxometry using steady-state prepared spiral multislice variable flip angle imaging.

PURPOSE

Variable flip angle (VFA) imaging is widely used for whole-brain T quantification. Because of the requirement to acquire at least two sets of MR images at different flip angles, VFA relaxometry is relatively slow. Here, whole-brain VFA T mapping at 1.5 T is accelerated by using efficient spiral non-Cartesian imaging METHODS: To quantify T in the human brain, radiofrequency spoiled gradient-echo imaging is performed at two optimized flip angles using an interleaved 2D multislice sequence with high spoiling efficiency. The acquisitions are accelerated by using a spiral trajectory with 10 interleaves combined with a dedicated magnetization preparation to ensure steady-state conditions in minimal time.

RESULTS

The investigated MR scan protocol allowed the acquisition of whole-brain T maps at a clinically relevant resolution in only 40 s (0.7 s per slice) with high reproducibility. White and gray matter T peaks clearly could be delineated by calculation of whole-brain T histograms, and the delivered T values showed good agreement with the reference method in selected regions of interest.

CONCLUSION

Due to the use of a fast spiral k-space trajectory, whole-brain VFA T mapping could be accelerated by an order of magnitude compared to conventional Cartesian sampling. Magn Reson Med 79:856-866, 2018. © 2017 International Society for Magnetic Resonance in Medicine.