Crum W R, Berry E, Ridgway J P, Sivananthan U M, Tan L B, Smith M A
Centre of Medical Imaging Research, University of Leeds, UK.
J Magn Reson Imaging. 1998 Sep-Oct;8(5):1040-50. doi: 10.1002/jmri.1880080507.
Simulation of MR images is a useful tool for offline sequence development and as an aid to understanding image formation. One particular application of simulation is MR tagging, which is used for tracking myocardial motion. Simple spatial-domain methods cannot adequately represent effects common in these images, such as motion artifact and signal wrap. An existing frequency-domain model is shown to be inappropriate for tagged images, and an extension based on the Bloch equations and Fourier shift theorem is described to correct this. Software incorporating the new model is used to generate ideal tag intensity profiles and to accurately simulate tagged images. The shifted k-space patterns associated with tagged images, and their dependence on the order of the binomial tagging sequence, are explained. An application of the Fourier shift theorem is suggested that allows more rapid simulation of static tagged images.
磁共振图像模拟是序列离线开发的有用工具，有助于理解图像形成。模拟的一个特殊应用是磁共振标记，用于跟踪心肌运动。简单的空间域方法无法充分体现这些图像中常见的效应，如运动伪影和信号包裹。已证明现有的频域模型不适用于标记图像，因此描述了一种基于布洛赫方程和傅里叶频移定理的扩展模型来纠正这一问题。结合新模型的软件用于生成理想的标记强度分布图，并准确模拟标记图像。解释了与标记图像相关的k空间偏移模式及其对二项式标记序列阶数的依赖性。还提出了傅里叶频移定理的一种应用，可实现静态标记图像的更快速模拟。
