Theoretical and experimental evaluation of phase‐dispersion effects caused by brain motion in diffusion and perfusion MR imaging
Theoretical and experimental evaluation of phase‐dispersion effects caused by brain motion in diffusion and perfusion MR imaging
复制标题
扩散和灌注磁共振成像中脑运动引起的相色散效应的理论和实验评估
DOI：
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发表时间：
1996
影响因子：
4.4
通讯作者：
F. Ståhlberg
中科院分区：
文献类型：
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作者：
R. Wirestam;D. Greitz;C. Thomsen;S. Brockstedt;M. Olsson;F. Ståhlberg
我们研究了扩散自旋回波脉冲序列中由脉动的脑运动引起的体素内相位色散。数学模型用于描述人脑运动的空间和时间速度分布。脑组织速度的空间分布在一个体素上引入了相位扩散，导致信号丢失。从理论上估计了这一信号损失，并评估了对观测扩散系数和灌流毛细血管分数的影响。当使用没有运动补偿的扩散脉冲序列的参数，并假设心电信号以不适当的延迟时间触发时，由脑运动引起的相位离散造成的最大信号损失为21%。这相当于高估了95%的扩散系数，并且灌注分数误差很小。对运动补偿脉冲序列的相应计算预测，由于不希望的相位色散，信号损失为1%到1.5%，而实验结果表明，与大脑运动有关的信号损失为4%。
We investigated intravoxel phase dispersion caused by pulsatile brain motion in diffusion spin‐echo pulse sequences. Mathematical models were used to describe the spatial and temporal velocity distributions of human brain motion. The spatial distribution of brain‐tissue velocity introduces a phase spread over one voxel, leading to signal loss. This signal loss was estimated theoretically, and effects on observed diffusion coefficient and perfused capillary fraction were assessed. When parameters from a diffusion pulse sequence without motion compensation were used, and ECG triggering with inappropriate delay times was assumed, the maximal signal loss caused by brain‐motion‐induced phase dispersion was predicted to be 21%. This corresponds to a 95% overestimation of the diffusion coefficient, and the perfusion‐fraction error was small. Corresponding calculations for motion‐compensated pulse sequences predicted a 1% to 1.5% signal loss due to undesired phase dispersion, whereas experimental results indicated a signal loss related to brain motion of 4%.