Barsky D, Pütz B, Schulten K
Department of Biophysics, University of Illinois at Urbana/Champaign, Urbana, USA.
Magn Reson Med. 1997 May;37(5):666-75. doi: 10.1002/mrm.1910370507.
A new model of compartmentalized relaxation--that which occurs for spins (protons) exchanging between compartments of different relaxation rates--is presented. This model generalizes previous ones by allowing spatially dependent relaxation within compartments. Solutions for the diffusion-Bloch equations are found via an efficient numerical technique known as the generalized moment expansion, and they agree well with the solutions to the standard two-site exchange equations (TSEE) for many typical situations. Specific models are developed for liposomes, red blood cells, capillaries, and arteries with respect to applied contrast agents. A parameter derived from tissue characteristics is introduced to predict the nature of the solutions. A new method is proposed for using contrast agents to detect capillaries, which exploits their high surface-to-volume ratio relative to the other elements of the vasculature.
提出了一种新的分隔弛豫模型——即自旋（质子）在具有不同弛豫率的隔室之间交换时发生的弛豫模型。该模型通过允许隔室内存在空间相关的弛豫，对先前的模型进行了推广。通过一种称为广义矩展开的有效数值技术，找到了扩散 - 布洛赫方程的解，并且在许多典型情况下，这些解与标准双位点交换方程（TSEE）的解非常吻合。针对脂质体、红细胞、毛细血管和动脉，结合应用的造影剂，开发了具体模型。引入了一个从组织特征导出的参数来预测解的性质。提出了一种利用造影剂检测毛细血管的新方法，该方法利用了毛细血管相对于脉管系统其他元素的高表面积与体积比。
