REDUCTION OF SUSCEPTIBILITY EFFECTS IN BOLD FMRI USING TAILORED RF PULSES: BRAIN

简介：高速fMRI是可取的，因为它允许（1） 动态成像功能事件;（2）减少运动伪影。 部分k空间（PK）成像通过收集更少的相位来提高速度 编码，同时保持空间分辨率。 PK也可以用于 读出方向，以减少回波时间，从而减少流量 和/或磁化率失相。 本研究探讨了 PK功能磁共振成像技术。 方法：采用GE 1.5T磁共振成像仪采集数据 扫描仪 运动皮层激活图像通过运行 GRE-EPI（单层4 mm切片，TR/TE/FOV = 375 ms/40 ms/240 mm，4次激发，160 240帧，128 x128矩阵，手指并置在 左手和右手每20秒）和2D螺旋序列（8个切片 3 mm厚度，TR/TE/FA/FOV = 640 ms/40 ms/63 °/240 mm，4个交错， 256秒内100帧，休息状态与右手手指交替 每隔20秒敲击一次）。 将螺旋数据重新网格化到128 x128 傅立叶网格，使PK模拟可以进行。 PK 使用零差方法进行重建。 结果如下： PK激活模式与FK的激活模式高度相似。 虽然 PK图像比FK图像具有降低的SNR，它们没有降低 空间分辨率也没有显著的振铃或模糊。 讨论 结论：我们的结果证明了PK功能磁共振成像的可行性 法 2D PK技术可以节省近1/2的扫描时间，而 3D PK扫描可以获得接近4倍的时间分辨率。 节省的时间可以用来收集更多的帧，以增加 统计功效或覆盖更多切片。 每个人减少的时间 时间范围允许使用更长的TR，从而改善CNR和/或 流入特性 每帧相同的时间可用于 增加空间分辨率。 考虑到PK 成像技术是广泛可用的，它代表了一个有前途的 脑功能图的方法。

Introduction: High speed fMRI is desirable since it allows (1) dynamically imaging functional events; (2) reducing motion artifacts. Partial k-space (PK) imaging increases speed by collecting fewer phase encodes while preserving spatial resolution. PK can also be used in the readout direction to reduce echo time, leading to reduced flow and/or susceptibility dephasing. This study examines the feasibility of PK fMRI technique. Method: MR data were acquired on a GE 1.5 T scanner. Motor cortex activation images were obtained by running a GRE-EPI (single 4mm slice, TR/TE/FOV = 375ms/40ms/240mm, 4 shots, 160 frames in 240s, 128x128 matrix, finger apposition alternated between the left and right hands every 20s) and a 2D spiral sequence (8 slices of 3mm thickness, TR/TE/FA/FOV = 640ms/40ms/ 63o/240mm, 4 interleaves, 100 frames in 256s, resting state alternated with right hand finger tapping every 20s). The spiral data were regridded onto a 128x128 Fourier grid so that PK simulation could be carried out. PK reconstruction was performed using the homodyne approach. Results: The PK activation patterns are highly similar to that of FK. Although PK images have reduced SNR than the FK images, they don't have reduced spatial resolution nor significant ringing or blurring. Discussion and Conclusions: Our results demonstrate the feasibility of PK fMRI technique. A 2D PK technique can save nearly 1/2 scan time, while a 3D PK scan can obtain close to 4 times higher temporal resolution. The time savings can be used to collect more frames to increase statistical power or to cover more slices. The reduced time for each time frame allows using longer TR, leading to improved CNR and/or inflow charateristics. The same time per frame can be used to increase spatial resolution if so desired. Considering that PK imaging techniques are widely available, it represents a promising approach for brain functional mapping.