Meyer C R, Williams D M
Department of Radiology, University of Michigan Hospitals, Ann Arbor 48109.
Med Phys. 1988 Jan-Feb;15(1):1-6. doi: 10.1118/1.596291.
A simple conceptual model for describing the effects of one-dimensional bulk flow on image intensities is presented and validated using a multislice imaging sequence specific to one vendor. The model allows quantitative estimates of echo amplitudes versus velocity by using the equation of motion to follow the pulse history of fluid volumes influenced by the readout pulse for any slice of interest. Each affected volume is divided into equal elemental components and the state of each component is computed at discrete times in a pulse position-timing diagram until readout occurs. The final amplitude for the composite volume is determined by the signed summation of each of the elemental components. Validation of the quantitative model was performed by imaging a rotating bulk flow phantom centered at each of the slices of a multislice, partial saturation, spin-echo sequence. Effects due to rf field inhomogeneities were normalized by dividing the results of the dynamic scans by the corresponding static one. The results presented here are relatively insensitive to odd-echo dephasing (even echo rephasing).
提出了一个用于描述一维体积流对图像强度影响的简单概念模型，并使用特定于某一厂商的多层成像序列进行了验证。该模型通过运动方程跟踪感兴趣的任何切片上受读出脉冲影响的流体体积的脉冲历史，从而对回波幅度与速度进行定量估计。每个受影响的体积被划分为相等的基本成分，并在脉冲位置 - 定时图中的离散时间计算每个成分的状态，直到读出发生。复合体积的最终幅度由每个基本成分的带符号求和确定。通过对以多层部分饱和自旋回波序列的每个切片为中心的旋转体积流体模进行成像，对定量模型进行了验证。通过将动态扫描结果除以相应的静态扫描结果，对射频场不均匀性引起的影响进行了归一化。此处给出的结果对奇数回波失相（偶数回波重聚）相对不敏感。
