Hua Jun, Qin Qin, van Zijl Peter C M, Pekar James J, Jones Craig K
The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
Magn Reson Med. 2014 Dec;72(6):1530-40. doi: 10.1002/mrm.25055. Epub 2013 Dec 12.
A new acquisition scheme for T2-weighted spin-echo BOLD fMRI is introduced.
It uses a T2-preparation module to induce blood-oxygenation-level-dependent (BOLD) contrast, followed by a single-shot three-dimensional (3D) fast gradient-echo readout with short echo time (TE). It differs from most spin-echo BOLD sequences in that BOLD contrast is generated before the readout, which eliminates the "dead time" due to long TE required for T2 contrast, and substantially improves acquisition efficiency. This approach, termed "3D T2prep-GRE," was implemented at 7 Tesla (T) with a typical spatial (2.5 × 2.5 × 2.5 mm(3) ) and temporal (TR = 2.3 s) resolution for functional MRI (fMRI) and whole-brain coverage (55 slices), and compared with the widely used 2D spin-echo EPI sequence.
In fMRI experiments of simultaneous visual/motor activities, 3D T2prep-GRE showed minimal distortion and little signal dropout across the whole brain. Its lower power deposition allowed greater spatial coverage (55 versus 17 slices with identical TR, resolution and power level), temporal SNR (60% higher) and CNR (35% higher) efficiency than 2D spin-echo EPI. It also showed smaller T2* contamination.
This approach is expected to be useful for ultra-high field fMRI, especially for regions near air cavities. The concept of using T2-preparation to generate BOLD contrast can be combined with many other sequences at any field strength.
介绍一种用于T2加权自旋回波BOLD功能磁共振成像的新采集方案。
该方案使用一个T2准备模块来诱导血氧水平依赖（BOLD）对比，随后采用具有短回波时间（TE）的单次三维（3D）快速梯度回波读出。它与大多数自旋回波BOLD序列的不同之处在于，BOLD对比是在读出之前生成的，这消除了由于T2对比所需的长TE导致的“死时间”，并显著提高了采集效率。这种方法被称为“3D T2prep-GRE”，在7特斯拉（T）磁场下实施，具有典型的空间分辨率（2.5×2.5×2.5 mm³）和时间分辨率（TR = 2.3 s）用于功能磁共振成像（fMRI）和全脑覆盖（55层），并与广泛使用的二维自旋回波EPI序列进行比较。
在同时进行视觉/运动活动的fMRI实验中，3D T2prep-GRE在全脑显示出最小的失真和极少的信号丢失。与二维自旋回波EPI相比，其较低的功率沉积允许更大的空间覆盖（在相同TR、分辨率和功率水平下为55层对17层）、更高的时间信噪比（高60%）和对比噪声比（高35%）效率。它还显示出较小的T2*污染。
这种方法有望用于超高场fMRI，特别是对于靠近气腔的区域。利用T2准备来生成BOLD对比的概念可以与任何场强下的许多其他序列相结合。
