Liu Thomas T, Wong Eric C, Frank Lawrence R, Buxton Richard B
Department of Radiology, University of California at San Diego, La Jolla, California, 92093, USA.
Neuroimage. 2002 May;16(1):269-82. doi: 10.1006/nimg.2001.1038.
Perfusion-based functional magnetic resonance imaging (fMRI) using arterial spin labeling (ASL) methods has the potential to provide better localization of the functional signal to the sites of neural activity compared to blood oxygenation level-dependent (BOLD) contrast fMRI. At present, experiments using ASL have been limited to simple block and periodic single-trial designs. We present here an adaptation of the general linear model to perfusion-based fMRI that enables the design and analysis of more complicated designs, such as random and semirandom event-related designs. Formulas for the least-squares estimate of the perfusion response and the F statistic for the detection of a response are derived. Exact expressions and useful approximations for detection power and estimation efficiency are presented, and it is shown that the trade-off between power and efficiency for perfusion experiments is similar to that previously observed for BOLD experiments. The least-squares estimate is compared with an estimate formed from the running subtraction of tag and control images. The running subtraction estimate is shown to be approximately equal to a temporally low-pass-filtered version of the least-squares estimate. Numerical simulations and results from ASL experiments are used to support the theoretical findings.
与基于血氧水平依赖（BOLD）对比的功能磁共振成像（fMRI）相比，使用动脉自旋标记（ASL）方法的基于灌注的功能磁共振成像（fMRI）有潜力将功能信号更好地定位到神经活动部位。目前，使用ASL的实验仅限于简单的组块和周期性单次试验设计。我们在此展示了通用线性模型在基于灌注的fMRI中的一种应用，它能够设计和分析更复杂的设计，比如随机和半随机事件相关设计。推导了灌注响应的最小二乘估计公式以及用于检测响应的F统计量。给出了检测功效和估计效率的精确表达式及有用的近似值，结果表明灌注实验中功效和效率之间的权衡与之前在BOLD实验中观察到的类似。将最小二乘估计与通过标记图像和对照图像的连续相减形成的估计进行了比较。结果表明，连续相减估计近似等于最小二乘估计的时间低通滤波版本。数值模拟和ASL实验结果用于支持理论发现。
