Data from: Model-based acceleration of Look-Locker T1 mapping

Mapping the longitudinal relaxation time T1 has widespread applications in clinical MRI as it promises a quantitative comparison of tissue properties across subjects and scanners. Due to the long scan times of conventional methods, however, the use of quantitative MRI in clinical routine is still very limited. In this work, an acceleration of Inversion-Recovery Look-Locker (IR-LL) T1 mapping is presented. A model-based algorithm is used to iteratively enforce an exponential relaxation model to a highly undersampled radially acquired IR-LL dataset obtained after the application of a single global inversion pulse. Using the proposed technique, a T1 map of a single slice with 1.6mm in-plane resolution and 4mm slice thickness can be reconstructed from data acquired in only 6s. A time-consuming segmented IR experiment was used as gold standard for T1 mapping in this work. In the subsequent validation study, the model-based reconstruction of a single-inversion IR-LL dataset exhibited a T1 difference of less than 2.6% compared to the segmented IR-LL reference in a phantom consisting of vials with T1 values between 200ms and 3000ms. In vivo, the T1 difference was smaller than 5.5% in WM and GM of seven healthy volunteers. Additionally, the T1 values are comparable to standard literature values. Despite the high acceleration, all model-based reconstructions were of a visual quality comparable to fully sampled references. Finally, the reproducibility of the T1 mapping method was demonstrated in repeated acquisitions. In conclusion, the presented approach represents a promising way for fast and accurate T1 mapping using radial IR-LL acquisitions without the need of any segmentation.

纵向弛豫时间T1成像（T1 mapping）在临床磁共振成像（MRI）中应用广泛，其可实现不同受试者与扫描仪间的组织特性定量对比。然而，传统方法扫描时长过长，导致定量MRI在临床常规诊疗中的应用仍极为受限。本研究提出一种针对反转恢复Look-Locker（Inversion-Recovery Look-Locker, IR-LL）T1成像的加速方案：采用基于模型的算法，将指数弛豫模型迭代适配至单次全局反转脉冲后采集的高欠采样径向IR-LL数据集。借助该方案，仅需6秒的采集数据即可重建出平面内分辨率1.6mm、层厚4mm的单层面T1图。本研究以耗时较长的分段反转恢复（IR）实验作为T1成像的金标准参照。后续验证实验结果显示，针对由T1值介于200ms至3000ms的试管组成的体模，单反转IR-LL数据集的基于模型重建结果与分段IR-LL参照相比，T1值差异小于2.6%。活体实验中，7名健康志愿者的白质（White Matter, WM）与灰质（Gray Matter, GM）的T1值差异均小于5.5%，且测得的T1值与已发表的标准文献数据具有良好一致性。尽管实现了极高的加速比，所有基于模型的重建结果的视觉质量均可与全采样参照相媲美。最后，通过重复采集实验验证了该T1成像方法的可重复性。综上，本研究提出的方法无需任何分割步骤，即可通过径向IR-LL采集实现快速且精准的T1成像，是一种极具应用潜力的方案。