Ultrafast and robust T 2 mapping using optimized single‐shot multi‐echo planar imaging with alternating blips

Abstract Purpose To develop a rapid, motion‐robustT 2$$ {\mathrm{T}}_2 $$ 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 measureT 2$$ {\mathrm{T}}_2 $$ 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 referenceT 2$$ {\mathrm{T}}_2 $$ values, indicating high precision and repeatability. In vivo, brainT 2$$ {\mathrm{T}}_2 $$ maps exhibited similar anatomical detail and tissue contrast as a reference sequence, withT 2$$ {\mathrm{T}}_2 $$ values of 70.0 ±$$ \kern0.5em \pm \kern0.5em $$  4.0 ms for gray matter, 56.8 ±$$ \kern0.5em \pm \kern0.5em $$  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.T 2$$ {\mathrm{T}}_2 $$ 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, accurateT 2$$ {\mathrm{T}}_2 $$ relaxation mapping by correcting distortion and mitigating motion artifacts. This sequence enhances the clinical feasibility of quantitativeT 2$$ {\mathrm{T}}_2 $$ mapping across diverse patient populations and body areas.