Multiplexed echo planar imaging for sub-second whole brain FMRI and fast diffusion imaging.
Multiplexed echo planar imaging for sub-second whole brain FMRI and fast diffusion imaging.
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DOI：
10.1371/journal.pone.0015710
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发表时间：
2010-12-20
期刊：
影响因子：
3.7
通讯作者：
Yacoub E
中科院分区：
文献类型：
--
作者：
Feinberg DA;Moeller S;Smith SM;Auerbach E;Ramanna S;Gunther M;Glasser MF;Miller KL;Ugurbil K;Yacoub E
回声平面成像(EPI)是一种对神经科学具有特殊价值的磁共振成像技术，它用于几乎所有的功能磁共振成像(FMRI)和人脑中纤维连接的扩散成像。EPI在不到一秒的时间内生成一张2D图像；然而，fMRI需要2-3秒才能获得多层全脑覆盖，扩散成像需要更长的时间。在这里，我们报告了在3特斯拉和7特斯拉时EPI全脑扫描时间的大幅减少，而没有显著牺牲空间分辨率，同时获得了功能敏感性。多路传输EPI(M-EPI)脉冲序列结合了两种形式的多路传输：利用同时回波重聚焦(SIR)EPI的时间多路传输(M)和具有多频带RF脉冲(MB)的空间多路传输(N)，以获得EPI回波序列中的m×n个图像，而不是正常的单个图像。这使得在3特斯拉下进行全脑功能磁共振成像的EPI扫描时间空前缩短，与更传统的2.5秒扫描时间相比，可实现400毫秒和800毫秒的扫描时间，并将神经元纤维轨迹的哈迪成像扫描时间缩短2-4倍。在7特斯拉的SIR成像的同时SE重聚焦通过使用更少的RF重聚焦脉冲和通过将FAT信号移出图像平面从而不需要脂肪抑制脉冲来有利地降低了SAR。在通过独立成分分析确定的静息状态功能网络的初步研究中，6倍高的采样率使峰值功能灵敏度增加了60%。这种新的M-EPI脉冲序列显著提高了全脑fMRI的时间分辨率，因此，这种新的方法可以用于研究网络中的非平稳性，并普遍用于扩展和丰富功能信息。
Echo planar imaging (EPI) is an MRI technique of particular value to neuroscience, with its use for virtually all functional MRI (fMRI) and diffusion imaging of fiber connections in the human brain. EPI generates a single 2D image in a fraction of a second; however, it requires 2–3 seconds to acquire multi-slice whole brain coverage for fMRI and even longer for diffusion imaging. Here we report on a large reduction in EPI whole brain scan time at 3 and 7 Tesla, without significantly sacrificing spatial resolution, and while gaining functional sensitivity. The multiplexed-EPI (M-EPI) pulse sequence combines two forms of multiplexing: temporal multiplexing (m) utilizing simultaneous echo refocused (SIR) EPI and spatial multiplexing (n) with multibanded RF pulses (MB) to achieve m×n images in an EPI echo train instead of the normal single image. This resulted in an unprecedented reduction in EPI scan time for whole brain fMRI performed at 3 Tesla, permitting TRs of 400 ms and 800 ms compared to a more conventional 2.5 sec TR, and 2–4 times reductions in scan time for HARDI imaging of neuronal fibertracks. The simultaneous SE refocusing of SIR imaging at 7 Tesla advantageously reduced SAR by using fewer RF refocusing pulses and by shifting fat signal out of the image plane so that fat suppression pulses were not required. In preliminary studies of resting state functional networks identified through independent component analysis, the 6-fold higher sampling rate increased the peak functional sensitivity by 60%. The novel M-EPI pulse sequence resulted in a significantly increased temporal resolution for whole brain fMRI, and as such, this new methodology can be used for studying non-stationarity in networks and generally for expanding and enriching the functional information.
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影响因子：
4.4
作者：
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通讯作者：
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作者：
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DOI：
10.1098/rstb.2005.1634
发表时间：
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