Ultrafast and robust mapping using optimized single-shot multi-echo planar imaging with alternating blips.

PURPOSE

To develop a rapid, motion-robust mapping technique suitable for clinical use across the body, including traditionally challenging, motion-prone patient populations or body parts.

METHODS

A novel single-shot multi-echo spin-echo EPI sequence with alternating phase encoding direction on each echo was implemented. This sequence acquires multiple echoes to measure from a single RF excitation. The alternating phase encoding gradient polarity enables the correction of geometric distortions in EPI using post-processing software. Stimulated echoes were removed by optimizing spoiler gradients. Diffusion MRI can also be achieved by incorporating diffusion-encoding gradients.

RESULTS

Phantom experiments showed no significant difference between measured and reference values, indicating high precision and repeatability. In vivo, brain maps exhibited similar anatomical detail and tissue contrast as a reference sequence, with values of 70.0   4.0 ms for gray matter, 56.8   3.4 ms for the white matter at a magnetic field strength of 3 Tesla. High-quality diffusion-weighted images with minimal distortion were generated, even at high b-values. mapping results from the kidney and fetal brain showcased the method's applicability across different anatomical regions and patient populations.

CONCLUSION

The single-shot multi-echo EPI sequence provided a basis for rapid, accurate relaxation mapping by correcting distortion and mitigating motion artifacts. This sequence enhances the clinical feasibility of quantitative mapping across diverse patient populations and body areas.