Simultaneous T₁, T₂ and T₂^⁎ mapping of the liver with multi-shot MI-SAGE

Purpose: To apply multi-shot high-resolution multi inversion spin and gradient echo (MI-SAGE) acquisition for simultaneous liver T₁, T₂ and T₂* mapping.

Methods: Inversion prepared spin- and gradient-echo EPI was developed with ascending slice order across measurements for efficient acquisition with T₁, T₂, and T₂^⁎ weighting. Multi-shot EPI was also implemented to minimize distortion and blurring while enabling high in-plane resolution. A dictionary-matching approach was used to fit the images to quantitative parameter maps, which were compared to T₁ measured by modified Look-Locker (MOLLI), T₁ measured by variable flip angle (VFA), T₂ measured by multiple echo time-based Half Fourier Single-shot Turbo spin-Echo (HASTE), T₂ measured by radial turbo-spin-echo (rTSE) and T₂^⁎ measured by multiple gradient echo (MGRE) sequences.

Results: The multi-shot variant of the sequence achieved higher in-plane resolution of 1.7 × 1.7 mm² with good image quality in 28 s. Derived quantitative maps showed comparable values to conventional mapping methods. As measured in phantom and in vivo, MOLLI, MESE and MGRE give closest values to MISAGE. VFA, HASTE and rTSE show obvious overestimation.

Conclusions: The proposed multi-shot inversion prepared spin- and gradient-echo EPI sequence allows for high-resolution quantitative T₁, T₂ and T₂ liver tissue characterization in a single breath-hold scan.