Cameron Donnie, Higgins David M, Stehning Christian, Kouwenhoven Marc, Bouhrara Mustapha, Frenneaux Michael P, Dawson Dana K, Redpath Thomas W
The University of Aberdeen, Aberdeen, UK.
Philips Healthcare, Guildford, Surrey, UK.
Magn Reson Imaging. 2015 May;33(4):363-73. doi: 10.1016/j.mri.2015.02.004. Epub 2015 Feb 7.
The purpose of this work was to evaluate different magnetization preparation and readout sequences for modified Look-Locker inversion recovery (MOLLI) toward improved T1 mapping in the heart. Elements investigated include: catalyzation sequences to prepare the magnetization before readout, alternate k-space trajectories, a spoiled gradient recalled echo readout, and a 5b(3b)3b MOLLI sampling scheme ('b' denoting beats).
Conventional 3b(3b)3b(3b)5b MOLLI with a linear k-space trajectory was compared to four variants in simulations, in vitro and in vivo (at 3T). Variants were centric conventional MOLLI, centric-paired conventional MOLLI, linear 5b(3b)3b MOLLI and spoiled gradient recalled echo MOLLI. Each of these was applied with three magnetization catalyzation methods, and T1 measurement accuracy and precision were evaluated in simulations via a Monte Carlo algorithm, in a set of calibrated phantoms, and in ten healthy volunteers. Contrast-to-noise, heart rate dependence and B1+ dependence were also evaluated.
A linear k-space trajectory was superior in vitro to centric and centric-paired trajectories. Of the catalyzation methods, preparation of transverse magnetization only-using a linearly increasing flip angle catalyzation-improved MOLLI T1 measurement accuracy, precision, and map quality versus methods that include catalyzation of the longitudinal magnetization. The 5b(3b)3b MOLLI scheme offered comparable native T1 measurement accuracy and precision to conventional MOLLI, despite its shortened acquisition.
MOLLI T1 measurement accuracy, precision, and map quality depend on the method of catalyzation of magnetization prior to image acquisition, as well as on the readout method and MOLLI sampling scheme used.
本研究旨在评估改良Look-Locker反转恢复序列（MOLLI）中不同的磁化准备和读出序列，以改善心脏T1映射。研究的要素包括：读出前准备磁化的催化序列、交替的k空间轨迹、扰相梯度回波读出以及5b(3b)3b MOLLI采样方案（“b”表示心跳）。
将具有线性k空间轨迹的传统3b(3b)3b(3b)5b MOLLI与模拟、体外和体内（3T）的四种变体进行比较。变体包括中心传统MOLLI、中心配对传统MOLLI、线性5b(3b)3b MOLLI和扰相梯度回波MOLLI。每种变体均应用三种磁化催化方法，并通过蒙特卡罗算法在模拟中、一组校准体模中以及十名健康志愿者中评估T1测量的准确性和精密度。还评估了对比度噪声、心率依赖性和B1 +依赖性。
在体外，线性k空间轨迹优于中心和中心配对轨迹。在催化方法中，仅使用线性增加翻转角催化来制备横向磁化，与包括纵向磁化催化的方法相比，可提高MOLLI T1测量的准确性、精密度和映射质量。尽管采集时间缩短，但5b(3b)3b MOLLI方案在固有T1测量准确性和精密度方面与传统MOLLI相当。
MOLLI T1测量的准确性、精密度和映射质量取决于图像采集前磁化的催化方法，以及所使用的读出方法和MOLLI采样方案。
