Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands.
Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.
NMR Biomed. 2021 Jul;34(7):e4531. doi: 10.1002/nbm.4531. Epub 2021 Apr 26.
In this work, we propose a free-breathing magnetic resonance fingerprinting (MRF) method that can be used to obtain B -robust quantitative T maps of the abdomen in a clinically acceptable time. A three-dimensional MRF sequence with a radial stack-of-stars trajectory was implemented, and its k-space acquisition ordering was adjusted to improve motion-robustness in the context of MRF. The flip angle pattern was optimized using the Cramér-Rao Lower Bound, and the encoding efficiency of sequences with 300, 600, 900 and 1800 flip angles was evaluated. To validate the sequence, a movable multicompartment phantom was developed. Reference multiparametric maps were acquired under stationary conditions using a previously validated MRF method. Periodic motion of the phantom was used to investigate the motion-robustness of the proposed sequence. The best performing sequence length (600 flip angles) was used to image the abdomen during a free-breathing volunteer scan. When using a series of 600 or more flip angles, the estimated T values in the stationary phantom showed good agreement with the reference scan. Phantom experiments revealed that motion-related artifacts can appear in the quantitative maps and confirmed that a motion-robust k-space ordering is essential. The in vivo scan demonstrated that the proposed sequence can produce clean parameter maps while the subject breathes freely. Using this sequence, it is possible to generate B -robust quantitative maps of T and B next to M -weighted images under free-breathing conditions at a clinically usable resolution within 5 min.
在这项工作中，我们提出了一种自由呼吸的磁共振指纹成像（MRF）方法，可用于在可接受的临床时间内获得腹部的 B 稳健定量 T 图。实现了具有径向堆叠星轨迹的三维 MRF 序列，并调整了其 k 空间采集顺序，以提高 MRF 背景下的运动稳健性。使用克拉美罗下限优化了翻转角模式，并评估了具有 300、600、900 和 1800 个翻转角的序列的编码效率。为了验证该序列，开发了一个可移动的多腔室幻影。使用先前经过验证的 MRF 方法在静止条件下获取参考多参数图。使用幻影的周期性运动来研究所提出序列的运动稳健性。最佳性能序列长度（600 个翻转角）用于在自由呼吸志愿者扫描期间对腹部进行成像。当使用 600 个或更多翻转角系列时，静止幻影中的估计 T 值与参考扫描具有良好的一致性。幻影实验表明，定量图中可能会出现与运动相关的伪影，并证实运动稳健的 k 空间排序至关重要。体内扫描表明，该序列可在 5 分钟内以临床可用的分辨率在自由呼吸条件下生成 M 加权图像旁边的 B 稳健定量 T 和 B 图。
