Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Magn Reson Imaging. 2011 Feb;33(2):287-95. doi: 10.1002/jmri.22437.
To quantitate cerebral blood flow (CBF) in the entire brain using the 3D echo planar imaging (EPI) PULSAR (pulsed star labeling) technique.
The PULSAR technique was modified to 1) incorporate a nonselective inversion pulse to suppress background signal; 2) to use 3D EPI acquisition; and 3) to modulate flip angle in such a manner as to minimize the blurring resulting from T1 modulation along the slice encoding direction. Computation of CBF was performed using the general kinetic model (GKM). In a series of healthy volunteers (n = 12), we first investigated the effects of introducing an inversion pulse on the measured value of CBF and on the temporal stability of the perfusion signal. Next we investigated the effect of flip angle modulation on the spatial blurring of the perfusion signal. Finally, we evaluated the repeatability of the CBF measurements, including the influence of the measurement of arterial blood magnetization (a calibration factor for the GKM).
The sequence provides sufficient perfusion signal to achieve whole brain coverage in ≈ 5 minutes. Introduction of the inversion pulse for background suppression did not significantly affect computed CBF values, but did reduce the fluctuation in the perfusion signal. Flip angle modulation reduced blurring, resulting in higher estimates of gray matter (GM) CBF and lower estimates of white matter (WM) CBF. The repeatability study showed that measurement of arterial blood signal did not result in significantly higher error in the perfusion measurement.
Improvements in acquisition and sequence preparation presented here allow for better quantification and localization of perfusion signal, allowing for accurate whole-brain CBF measurements in 5 minutes.
使用 3D 回波平面成像（EPI）脉冲星标记（PULSAR）技术定量测量全脑脑血流（CBF）。
对 PULSAR 技术进行了修改，以 1）纳入非选择性反转脉冲来抑制背景信号；2）使用 3D EPI 采集；3）以最小化沿切片编码方向的 T1 调制引起的模糊的方式调制翻转角。使用通用动力学模型（GKM）计算 CBF。在一系列健康志愿者（n=12）中，我们首先研究了引入反转脉冲对测量的 CBF 值和灌注信号的时间稳定性的影响。接下来，我们研究了翻转角调制对灌注信号空间模糊的影响。最后，我们评估了 CBF 测量的可重复性，包括动脉血磁化测量的影响（GKM 的校准因子）。
该序列提供了足够的灌注信号，大约 5 分钟即可完成全脑覆盖。引入反转脉冲进行背景抑制不会显著影响计算出的 CBF 值，但确实降低了灌注信号的波动。翻转角调制减少了模糊，导致灰质（GM）CBF 的估计值更高，白质（WM）CBF 的估计值更低。重复性研究表明，测量动脉血信号不会导致灌注测量的显著更高误差。
此处提出的采集和序列准备方面的改进可更好地量化和定位灌注信号，从而在 5 分钟内实现准确的全脑 CBF 测量。
