Cheng K H
Physics Department, Texas Tech University, Lubbock 79409.
Magn Reson Imaging. 1993;11(4):569-83. doi: 10.1016/0730-725x(93)90476-t.
The non-Einstein diffusion behavior of water in a model biological tissue system, intact duck embryos, has been investigated by the use of an in vivo proton pulsed-gradient spin-echo (PGSE) MR imaging technique. Multiple-frame MR images of the intact duck embryos and control solution (0.5 mM CuSO4 doped water) were acquired systematically at different diffusion times and strengths of the diffusion-sensitizing magnetic field gradients of the PGSE sequence. These raw images were then used to generate various dynamic (self-diffusion coefficient) and structural (fractal, residual attenuation, and compartment fraction) diffusion parameter maps of water in the imaging objects on the basis of different Einstein and higher order (non-Brownian, Residual, and 2-compartment) diffusion models. The self-diffusion coefficients of the body tissues of the embryos obtained from all diffusion models were significantly lower than those of the surrounding embryonic fluid. The structural diffusion parameter maps obtained from the higher order diffusion models revealed that water molecules exhibited either non-Brownian, restricted, or compartmentalized diffusion behavior in the embryonic tissues, but Einstein or Brownian diffusion behavior in the embryonic fluid and control solution. The diffusion parameter maps, both dynamic and structural, were found to provide much better contrasts than the conventional relaxation time (T1, T2, and biexponential T2) maps in separating the tissues from the surrounding embryonic fluid in the duck embryos. The mathematical models and procedures for generating the dynamic and structural diffusion parameter maps are also presented in this paper.
利用体内质子脉冲梯度自旋回波（PGSE）磁共振成像技术，研究了水在模型生物组织系统——完整鸭胚胎中的非爱因斯坦扩散行为。在不同扩散时间以及PGSE序列扩散敏感磁场梯度强度下，系统采集了完整鸭胚胎和对照溶液（0.5 mM硫酸铜掺杂水）的多帧磁共振图像。然后，基于不同的爱因斯坦及高阶（非布朗、残余和双室）扩散模型，利用这些原始图像生成成像对象中水的各种动态（自扩散系数）和结构（分形、残余衰减和隔室分数）扩散参数图。从所有扩散模型获得的胚胎身体组织的自扩散系数显著低于周围胚胎液的自扩散系数。从高阶扩散模型获得的结构扩散参数图显示，水分子在胚胎组织中表现出非布朗、受限或隔室化扩散行为，但在胚胎液和对照溶液中表现出爱因斯坦或布朗扩散行为。发现在将鸭胚胎中的组织与周围胚胎液分离时，动态和结构扩散参数图比传统弛豫时间（T1、T2和双指数T2）图提供了更好的对比度。本文还介绍了生成动态和结构扩散参数图的数学模型和程序。
