Ultrafast T2 and T2* mapping using single‐shot spatiotemporally encoded MRI with reduced field of view and spiral out‐in‐out‐in trajectory

Abstract

AbstractBackgroundT2 and T2* mapping are crucial components of quantitative magnetic resonance imaging, offering valuable insights into tissue characteristics and pathology. Single‐shot methods can achieve ultrafast T2 or T2* mapping by acquiring multiple readout echo trains. However, the extended echo trains pose challenges, such as compromised image quality and diminished quantification accuracy.PurposeIn this study, we develop a single‐shot method for ultrafast T2 and T2* mapping with reduced echo train length.MethodsThe proposed method is based on ultrafast single‐shot spatiotemporally encoded (SPEN) MRI combined with reduced field of view (FOV) and spiral out‐in‐out‐in (OIOI) trajectory. Specifically, a biaxial SPEN excitation scheme was employed to excite the spin signal into the spatiotemporal encoding domain. The OIOI trajectory with high acquisition efficiency was employed to acquire signals within targeted reduced FOV. Through non‐Cartesian super‐resolved (SR) reconstruction, 12 aliasing‐free images with different echo times were obtained within 150 ms. These images were subsequently fitted to generate T2 or T2* mapping simultaneously using a derived model.ResultsAccurate and co‐registered T2 and T2* maps were generated, closely resembling the reference maps. Numerical simulations demonstrated substantial consistency (R2 > 0.99) with the ground truth values. A mean difference of 0.6% and 1.7% was observed in T2 and T2*, respectively, in in vivo rat brain experiments compared to the reference. Moreover, the proposed method successfully obtained T2 and T2* mappings of rat kidney in free‐breathing mode, demonstrating its superiority over multishot methods lacking respiratory navigation.ConclusionsThe results suggest that the proposed method can achieve ultrafast and accurate T2 and T2* mapping, potentially facilitating the application of T2 and T2* mapping in scenarios requiring high temporal resolution.