Ibrahim El-Sayed H, Stuber Matthias, Schär Michael, Osman Nael F
Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21287, USA.
J Magn Reson Imaging. 2006 Nov;24(5):1159-67. doi: 10.1002/jmri.20730.
To improve the tag persistence throughout the whole cardiac cycle by providing a constant tag-contrast throughout all the cardiac phases when using balanced steady-state free precession (bSSFP) imaging.
The flip angles of the imaging radiofrequency pulses were optimized to compensate for the tagging contrast-to-noise ratio (Tag-CNR) fading at later cardiac phases in bSSFP imaging. Complementary spatial modulation of magnetization (CSPAMM) tagging was implemented to improve the Tag-CNR. Numerical simulations were performed to examine the behavior of the Tag-CNR with the proposed method, and to compare the resulting Tag-CNR with that obtained from the more commonly used spoiled gradient echo (SPGR) imaging. A gel phantom, as well as five healthy human volunteers, were scanned on a 1.5T scanner using bSSFP imaging with and without the proposed technique. The phantom was also scanned with SPGR imaging.
With the proposed technique, the Tag-CNR remained almost constant during the whole cardiac cycle. Using bSSFP imaging, the Tag-CNR was about double that of SPGR.
The tag persistence was significantly improved when the proposed method was applied, with better Tag-CNR during the diastolic cardiac phase. The improved Tag-CNR will support automated tagging analysis and quantification methods.
在使用平衡稳态自由进动（bSSFP）成像时，通过在所有心动周期阶段提供恒定的标记对比度，提高整个心动周期内的标记持久性。
优化成像射频脉冲的翻转角，以补偿bSSFP成像中较晚心动周期阶段标记对比度噪声比（Tag-CNR）的衰减。实施互补空间调制磁化（CSPAMM）标记以提高Tag-CNR。进行数值模拟以研究所提出方法下Tag-CNR的行为，并将所得Tag-CNR与更常用的扰相梯度回波（SPGR）成像所获得的Tag-CNR进行比较。使用带有和不带有所提出技术的bSSFP成像，在1.5T扫描仪上对凝胶体模以及五名健康人类志愿者进行扫描。该体模也用SPGR成像进行扫描。
使用所提出的技术，Tag-CNR在整个心动周期内几乎保持恒定。使用bSSFP成像时，Tag-CNR约为SPGR的两倍。
应用所提出的方法时，标记持久性显著提高，在舒张期心动周期阶段具有更好的Tag-CNR。改进的Tag-CNR将支持自动标记分析和量化方法。
