Liver-Buda-Sage: Simultaneous Whole Liver T2 And T2* Mapping In One Breath-Hold

We propose liver-BUDA-SAGE (liver Blip Up-Down Acquisition for Spin And Gradient Echo imaging), an efficient echo-planar imaging (EPI) sequence to rapidly obtain high resolution T2 and T2* quantitative mapping of human liver at 3.0 Tesla (T) with high-coverage and high geometric fidelity. This multi-shot navigator-free acquisition includes multiple T2* -, T2'- and T2-weighted contrasts with alternating phase-encoding polarities across the interleaved shots. A field map estimated from interim reconstructions was incorporated into the joint multi-shot EPI reconstruction with a structured low-rank constraint to eliminate geometric distortion. An adapted quantitative multi-parametric mapping method was established using combined least-square solution and Bloch dictionary matching to obtain maps based on the reconstructed echoes. In-vivo results demonstrate the ability of liver BUDA-SAGE to provide high-coverage, distortion-free, multi-contrast images and quantitative T2/T2* maps at 1.5Г—1.5 mm2 in-plane resolution in ~20s for 16 slices. Estimated quantitative maps showed good agreement in phantom compared to conventional mapping methods with slight biases of 2.6 ms and -0.2 ms for T2 and T2*. Measured in-vivo liver values (meanВ±SD) for T2 and T2* were 21.26В±2.37 ms and 30.59В±3.70 ms which are consistent with those reported in the literature.