An exploration of task based fMRI in neonates using echo-shifting to allow acquisition at longer TE without loss of temporal efficiency
An exploration of task based fMRI in neonates using echo-shifting to allow acquisition at longer TE without loss of temporal efficiency
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DOI：
10.1016/j.neuroimage.2015.12.025
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发表时间：
2016-02-15
期刊：
影响因子：
5.7
通讯作者：
Hajnal, Joseph V.
中科院分区：
文献类型：
--
作者：
Ferrazzi, Giulio;Nunes, Rita G.;Hajnal, Joseph V.
在新生儿和胎儿fMRI的BOLD信号的最佳对比度噪声比一直难以实现，因为更长的T-2* 值在发育中的脑组织相比，在成熟的成年人的大脑。优化fMRI序列的传统方法建议匹配新生儿和胎儿大脑的回波时间（T-E）和T-2*。然而，使用一个长的回波时间通常会增加最小重复时间（T-R），从而导致效率低下的sampling.Here我们应用回波移位的概念，以实现改善的对比度噪声比和有效的数据采样在同一时间的新生儿fMRI任务为基础。回波移位EPI（es-EPI）是标准2D-EPI序列的修改，使回波时间长于连续激励之间的时间（T-E>T-S = T-R/N-S，其中N-S是采集的切片数量，T-S是切片间重复时间）。所提出的方法进行了测试新生儿受试者使用被动感觉运动任务范例。双回波EPI数据集的读出结构与es-EPI相同，并作为对照数据来评估BOLD activation.From后一种分析的结果，平均增加78 +/- 41%，对比噪声比是观察到的，当比较晚到短回波。此外，es-EPI允许以与后期回波相同的对比度采集数据，但更有效，因为可以在相同的时间内采集更多数量的切片。(C)2015 Elsevier Inc. All rights reserved.
Optimal contrast to noise ratio of the BOLD signal in neonatal and foetal fMRI has been hard to achieve because of the much longer T-2* values in developing brain tissue in comparison to those in the mature adult brain. The conventional approach of optimizing fMRI sequences would suggest matching the echo time (T-E) and the T-2* of the neonatal and foetal brain. However, the use of a long echo time would typically increase the minimum repetition time (T-R) resulting in inefficient sampling.Here we apply the concept of echo shifting to task based neonatal fMRI in order to achieve an improved contrast to noise ratio and efficient data sampling at the same time. Echo shifted EPI (es-EPI) is a modification of a standard 2D-EPI sequence which enables echo times longer than the time between consecutive excitations (T-E>T-S = T-R/N-S, where N-S is the number of acquired slices and T-S the inter-slice repetition time). The proposed method was tested on neonatal subjects using a passive sensori-motor task paradigm. Dual echo EPI datasets with an identical readout structure to es-EPI were also acquired and used as control data to assess BOLD activation.From the results of the latter analysis, an average increase of 78 +/- 41% in contrast to noise ratio was observable when comparing late to short echoes. Furthermore, es-EPI allowed the acquisition of data with an identical contrast to the late echo, but more efficiently since a higher number of slices could be acquired in the same amount of time. (C) 2015 Elsevier Inc. All rights reserved.