Cohen Alexander D, Nencka Andrew S, Lebel R Marc, Wang Yang
Department of Radiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America.
GE Healthcare, Calgary, Alberta, Canada.
PLoS One. 2017 Mar 2;12(3):e0169253. doi: 10.1371/journal.pone.0169253. eCollection 2017.
A novel sequence has been introduced that combines multiband imaging with a multi-echo acquisition for simultaneous high spatial resolution pseudo-continuous arterial spin labeling (ASL) and blood-oxygenation-level dependent (BOLD) echo-planar imaging (MBME ASL/BOLD). Resting-state connectivity in healthy adult subjects was assessed using this sequence. Four echoes were acquired with a multiband acceleration of four, in order to increase spatial resolution, shorten repetition time, and reduce slice-timing effects on the ASL signal. In addition, by acquiring four echoes, advanced multi-echo independent component analysis (ME-ICA) denoising could be employed to increase the signal-to-noise ratio (SNR) and BOLD sensitivity. Seed-based and dual-regression approaches were utilized to analyze functional connectivity. Cerebral blood flow (CBF) and BOLD coupling was also evaluated by correlating the perfusion-weighted timeseries with the BOLD timeseries. These metrics were compared between single echo (E2), multi-echo combined (MEC), multi-echo combined and denoised (MECDN), and perfusion-weighted (PW) timeseries. Temporal SNR increased for the MECDN data compared to the MEC and E2 data. Connectivity also increased, in terms of correlation strength and network size, for the MECDN compared to the MEC and E2 datasets. CBF and BOLD coupling was increased in major resting-state networks, and that correlation was strongest for the MECDN datasets. These results indicate our novel MBME ASL/BOLD sequence, which collects simultaneous high-resolution ASL/BOLD data, could be a powerful tool for detecting functional connectivity and dynamic neurovascular coupling during the resting state. The collection of more than two echoes facilitates the use of ME-ICA denoising to greatly improve the quality of resting state functional connectivity MRI.
一种新的序列被引入，该序列将多波段成像与多回波采集相结合，用于同时进行高空间分辨率的伪连续动脉自旋标记（ASL）和血氧水平依赖（BOLD）回波平面成像（MBME ASL/BOLD）。使用该序列评估了健康成年受试者的静息态连接性。采集了四个回波，多波段加速因子为4，以提高空间分辨率、缩短重复时间并减少切片时间对ASL信号的影响。此外，通过采集四个回波，可以采用先进的多回波独立成分分析（ME-ICA）去噪来提高信噪比（SNR）和BOLD敏感性。基于种子点和双回归方法被用于分析功能连接性。还通过将灌注加权时间序列与BOLD时间序列进行相关性分析来评估脑血流量（CBF）和BOLD耦合。对单回波（E2）、多回波组合（MEC）、多回波组合并去噪（MECDN）和灌注加权（PW）时间序列的这些指标进行了比较。与MEC和E2数据相比，MECDN数据的时间SNR有所增加。与MEC和E2数据集相比，MECDN在相关强度和网络大小方面的连接性也有所增加。主要静息态网络中的CBF和BOLD耦合增加，并且对于MECDN数据集，这种相关性最强。这些结果表明，我们的新型MBME ASL/BOLD序列能够同时采集高分辨率的ASL/BOLD数据，可能是检测静息态功能连接性和动态神经血管耦合的有力工具。采集两个以上的回波有助于使用ME-ICA去噪，从而大大提高静息态功能连接性MRI的质量。
