Hu Shuowen, Olulade Olumide, Tamer Gregory G, Luh Wen-Ming, Talavage Thomas M
School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, USA.
J Magn Reson Imaging. 2009 May;29(5):1234-9. doi: 10.1002/jmri.21767.
To assess and model signal fluctuations induced by non-T(1)-related confounds in variable repetition time (TR) functional magnetic resonance imaging (fMRI) and to develop a compensation procedure to correct for the non-T(1)-related artifacts.
Radiofrequency disabled volume gradient sequences were effected at variable offsets between actual image acquisitions, enabling perturbation of the measurement system without perturbing longitudinal magnetization, allowing the study of non-T(1)-related confounds that may arise in variable TR experiments. Three imaging sessions utilizing a daily quality assurance (DQA) phantom were conducted to assess the signal fluctuations, which were then modeled as a second-order system. A modified projection procedure was implemented to correct for signal fluctuations arising from non-T(1)-related confounds, and statistical analysis was performed to assess the significance of the artifacts with and without compensation.
Assessment using phantom data reveals that the signal fluctuations induced by non-T(1)-related confounds was consistent in shape across the phantom and well-modeled by a second-order system. The phantom exhibited significant spurious detections (at P < 0.01) almost uniformly across the central slices of the phantom.
Second-order system modeling and compensation of non-T(1)-related confounds achieves significant reduction of spurious detection of fMRI activity in a phantom.
评估并建立可变重复时间（TR）功能磁共振成像（fMRI）中与非T(1)相关混淆因素引起的信号波动模型，并开发一种补偿程序以校正与非T(1)相关的伪影。
在实际图像采集之间以可变偏移量执行射频禁用的容积梯度序列，从而在不干扰纵向磁化的情况下对测量系统进行扰动，以便研究可变TR实验中可能出现的与非T(1)相关的混淆因素。利用每日质量保证（DQA）体模进行了三次成像实验以评估信号波动，然后将其建模为二阶系统。实施了一种改进的投影程序以校正由与非T(1)相关的混淆因素引起的信号波动，并进行了统计分析以评估有无补偿情况下伪影的显著性。
使用体模数据进行的评估表明，由与非T(1)相关的混淆因素引起的信号波动在整个体模中的形状是一致的，并且可以很好地用二阶系统建模。体模在几乎整个体模的中央切片上均表现出显著的伪检测（P < 0.01）。
对与非T(1)相关的混淆因素进行二阶系统建模和补偿可显著减少体模中fMRI活动的伪检测。
