Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China.
School of Medical Technology, Beijing Institute of Technology, Beijing, China.
NMR Biomed. 2022 Sep;35(9):e4755. doi: 10.1002/nbm.4755. Epub 2022 May 14.
The purpose of the current study was to develop and validate a three-dimensional (3D) free-breathing cardiac T -mapping sequence using SAturation-recovery and Variable-flip-Angle (SAVA). SAVA sequentially acquires multiple electrocardiogram-triggered volumes using a multishot spoiled gradient-echo sequence. The first volume samples the equilibrium signal of the longitudinal magnetization, where a flip angle of 2° is used to reduce the time for the magnetization to return to equilibrium. The succeeding three volumes are saturation prepared with variable delays, and are acquired using a 15° flip angle to maintain the signal-to-noise ratio. A diaphragmatic navigator is used to compensate the respiratory motion. T is calculated using a saturation-recovery model that accounts for the flip angle. We validated SAVA by simulations, phantom, and human subject experiments at 3 T. SAVA was compared with modified Look-Locker inversion recovery (MOLLI) and saturation-recovery single-shot acquisition (SASHA) in vivo. In phantoms, T by SAVA had good agreement with the reference (R = 0.99). In vivo 3D T mapping by SAVA could achieve an imaging resolution of 1.25 × 1.25 × 8 mm . Both global and septal T values by SAVA (1347 ± 37 and 1332 ± 42 ms) were in between those by SASHA (1612 ± 63 and 1618 ± 51 ms) and MOLLI (1143 ± 59 and 1188 ± 65 ms). According to the standard deviation (SD) and coefficient of variation (CV), T precision measured by SAVA (SD: 99 ± 14 and 60 ± 8 ms; CV: 7.4% ± 0.9% and 4.5% ± 0.6%) was comparable with MOLLI (SD: 99 ± 25 and 46 ± 12 ms; CV: 8.8% ± 2.5% and 3.9% ± 1.1%) and superior to SASHA (SD: 222 ± 89 and 132 ± 33 ms; CV: 13.8% ± 5.5% and 8.1% ± 2.0%). It was concluded that the proposed free-breathing SAVA sequence enables more efficient 3D whole-heart T estimation with good accuracy and precision.
本研究的目的是开发和验证一种使用 SAturation-recovery 和 Variable-flip-Angle（SAVA）的三维（3D）自由呼吸心脏 T 映射序列。SAVA 序列使用多 shot 扰相梯度回波序列顺序采集多个心电图触发的容积。第一个容积采集纵向磁化的平衡信号，其中使用 2°的翻转角来减少磁化返回平衡的时间。接下来的三个容积使用可变延迟进行饱和准备，并使用 15°的翻转角来保持信噪比。使用膈肌导航仪来补偿呼吸运动。T 通过考虑翻转角的饱和恢复模型来计算。我们在 3T 下通过模拟、体模和人体实验验证了 SAVA。SAVA 与改良的 Look-Locker 反转恢复（MOLLI）和饱和恢复单次采集（SASHA）进行了体内比较。在体模中，SAVA 的 T 值与参考值（R=0.99）吻合良好。SAVA 进行的体内 3D T 映射可达到 1.25×1.25×8mm 的成像分辨率。SAVA 的全局和间隔 T 值（1347±37 和 1332±42ms）均介于 SASHA（1612±63 和 1618±51ms）和 MOLLI（1143±59 和 1188±65ms）之间。根据标准偏差（SD）和变异系数（CV），SAVA 测量的 T 精度（SD：99±14 和 60±8ms；CV：7.4%±0.9%和 4.5%±0.6%）与 MOLLI（SD：99±25 和 46±12ms；CV：8.8%±2.5%和 3.9%±1.1%）相当，优于 SASHA（SD：222±89 和 132±33ms；CV：13.8%±5.5%和 8.1%±2.0%）。结论：所提出的自由呼吸 SAVA 序列能够更有效地进行 3D 全心 T 估计，具有良好的准确性和精度。
