Chen W, Ackerman J J
Department of Chemistry, Washington University, St Louis, MO 63130-4899.
NMR Biomed. 1990 Aug;3(4):147-57. doi: 10.1002/nbm.1940030402.
The use of a current-generated, inhomogeneous, surface-spoiling magnetic field gradient for enhancing magnetic resonance spatial localization, by rapidly inducing spin phase incoherence in surface lying regions of a sample is examined theoretically. A geometrically simple surface-spoiling magnetic field gradient coil design is presented and its gradient field characterized via computer simulations. Mathematical expressions describing the time dependence of net sample spin phase coherence under influence of the spoiling gradient are developed for application with homogeneous (B1) volume coils. The dependence of spoiling efficiency on the magnetogyric ratio of the nuclide under investigation and on the current driving the gradient field is described. Spoiling periods of ca 1-2 ms with driving currents of ca 0.5-1.0 A are predicted to be adequate for surface-spoiling experiments with rat, e.g., for noninvasive monitoring of liver. A companion article (W. Chen and J.J.H. Ackerman, NMR Biomed., 3, 158-165 (1990)) describes implementation of the surface-spoiling technique with multicompartment models (phantoms) and with rat in vivo.
理论上研究了利用电流产生的非均匀表面破坏磁场梯度来增强磁共振空间定位，该方法通过在样品的表面区域快速诱导自旋相位不相干来实现。提出了一种几何结构简单的表面破坏磁场梯度线圈设计，并通过计算机模拟对其梯度场进行了表征。针对均匀（B1）体积线圈的应用，推导了描述在破坏梯度影响下净样品自旋相位相干性随时间变化的数学表达式。阐述了破坏效率与所研究核素的旋磁比以及驱动梯度场电流之间的关系。预计对于大鼠的表面破坏实验，例如用于肝脏的无创监测，在约0.5 - 1.0 A的驱动电流下，约1 - 2 ms的破坏时间就足够了。一篇配套文章（W. Chen和J.J.H. Ackerman，《NMR Biomed.》，3，158 - 165（1990））描述了表面破坏技术在多隔室模型（体模）和大鼠体内的实施情况。
