Tran-Gia Johannes, Wech Tobias, Bley Thorsten, Köstler Herbert
Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany.
Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany; Comprehensive Heart Failure Center (CHFC) Würzburg, University of Würzburg, Würzburg, Germany.
PLoS One. 2015 Apr 10;10(4):e0122611. doi: 10.1371/journal.pone.0122611. eCollection 2015.
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成像在临床磁共振成像（MRI）中有着广泛应用，因为它有望对不同受试者和扫描仪之间的组织特性进行定量比较。然而，由于传统方法扫描时间长，定量MRI在临床常规检查中的应用仍然非常有限。在这项工作中，我们提出了一种对反转恢复锁相环（IR-LL）T1成像的加速方法。我们使用基于模型的算法，将指数弛豫模型迭代应用于在施加单个全局反转脉冲后获得的高度欠采样的径向采集IR-LL数据集中。使用所提出的技术，仅需6秒采集的数据就能重建出平面分辨率为1.6mm、层厚为4mm的单一层面的T1图谱。在这项工作中，耗时的分段IR实验被用作T1成像的金标准。在随后的验证研究中，对于由T1值在200ms至3000ms之间的小瓶组成的模型，单反转IR-LL数据集基于模型的重建与分段IR-LL参考相比，T1差异小于2.6%。在体内，7名健康志愿者的白质和灰质中的T1差异小于5.5%。此外，T1值与标准文献值相当。尽管加速程度很高，但所有基于模型的重建在视觉质量上都与全采样参考相当。最后，通过重复采集证明了T1成像方法的可重复性。总之，所提出的方法代表了一种有前景的方式，可使用径向IR-LL采集进行快速准确的T1成像，而无需任何分段。
