National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, USA.
Systems Neuroscience and Pain Lab, Stanford University, Stanford, California, USA.
Magn Reson Med. 2022 Apr;87(4):1846-1862. doi: 10.1002/mrm.29099. Epub 2021 Nov 24.
We investigate the influence of moving blood-attenuation effects when using "delay alternating with nutation for tailored excitation" (DANTE) pulses in conjunction with blood oxygen level dependent (BOLD) of functional MRI (fMRI) at 3 T. Based on the effects of including DANTE pulses, we propose quantification of cerebral blood volume (CBV) changes following functional stimulation.
Eighteen volunteers in total underwent fMRI scans at 3 T. Seven volunteers were scanned to investigate the effects of DANTE pulses on the fMRI signal. CBV changes in response to visual stimulation were quantified in 11 volunteers using a DANTE-prepared dual-echo EPI sequence.
The inflow effects from flowing blood in arteries and draining vein effects from flowing blood in large veins can be suppressed by use of a DANTE preparation module. Using DANTE-prepared dual-echo EPI, we quantitatively measured intravascular-weighted microvascular CBV changes of 25.4%, 29.8%, and 32.6% evoked by 1, 5, and 10 Hz visual stimulation, respectively. The extravascular fraction (∆S/S) at TE = 30 ms in total BOLD signal was determined to be 64.8 ± 3.4%, which is in line with previous extravascular component estimation at 3 T. Results show that the microvascular CBV changes are linearly dependent on total BOLD changes at TE = 30 ms with a slope of 0.113, and this relation is independent of stimulation frequency and subject.
The DANTE preparation pulses can be incorporated into a standard EPI fMRI sequence for the purpose of minimizing inflow effects and reducing draining veins effects in large vessels. Additionally, the DANTE-prepared dual-echo EPI sequence is a promising fast imaging tool for quantification of intravascular-weighted CBV change in the microvascular space at 3 T.
我们研究了在 3T 下使用“延迟交替反转激发”（DANTE）脉冲结合血氧水平依赖（BOLD）功能磁共振成像（fMRI）时，流动血液衰减效应对 DANTE 脉冲的影响。基于包括 DANTE 脉冲的效果，我们提出了对功能刺激后脑血容量（CBV）变化的定量评估。
总共 18 名志愿者在 3T 下进行了 fMRI 扫描。7 名志愿者接受扫描以研究 DANTE 脉冲对 fMRI 信号的影响。11 名志愿者使用 DANTE 准备的双回波 EPI 序列定量测量了视觉刺激后的 CBV 变化。
使用 DANTE 准备模块可以抑制动脉流入效应和大静脉中血流的引流静脉效应。使用 DANTE 准备的双回波 EPI，我们定量测量了 1、5 和 10Hz 视觉刺激分别引起的血管内加权微血管 CBV 变化为 25.4%、29.8%和 32.6%。在总 BOLD 信号中，TE = 30ms 的血管外分数（∆S/S）被确定为 64.8 ± 3.4%，与之前在 3T 下的血管外成分估计值一致。结果表明，在 TE = 30ms 时，微血管 CBV 变化与总 BOLD 变化呈线性相关，斜率为 0.113，这种关系与刺激频率和个体无关。
DANTE 准备脉冲可以被整合到标准的 EPI fMRI 序列中，以最小化流入效应并减少大血管中的引流静脉效应。此外，DANTE 准备的双回波 EPI 序列是一种有前途的快速成像工具，可用于量化 3T 下微血管空间内血管内加权 CBV 的变化。
