Grebenkov D S, Guillot G, Sapoval B
Dipartimento di Scienze Fisiche, Università di Napoli Federico II Complesso universitario Monte S. Angelo, Via Cintia, 80126 Naples, Italy.
J Magn Reson. 2007 Jan;184(1):143-56. doi: 10.1016/j.jmr.2006.09.026. Epub 2006 Oct 20.
A branched geometrical structure of the mammal lungs is known to be crucial for rapid access of oxygen to blood. But an important pulmonary disease like emphysema results in partial destruction of the alveolar tissue and enlargement of the distal airspaces, which may reduce the total oxygen transfer. This effect has been intensively studied during the last decade by MRI of hyperpolarized gases like helium-3. The relation between geometry and signal attenuation remained obscure due to a lack of realistic geometrical model of the acinar morphology. In this paper, we use Monte Carlo simulations of restricted diffusion in a realistic model acinus to compute the signal attenuation in a diffusion-weighted NMR experiment. We demonstrate that this technique should be sensitive to destruction of the branched structure: partial removal of the interalveolar tissue creates loops in the tree-like acinar architecture that enhance diffusive motion and the consequent signal attenuation. The role of the local geometry and related practical applications are discussed.
哺乳动物肺部的分支几何结构对于氧气快速进入血液至关重要。但像肺气肿这样的重要肺部疾病会导致肺泡组织部分破坏以及远端气腔扩大，这可能会减少总的氧气传输。在过去十年中，通过对诸如氦 - 3等超极化气体进行磁共振成像（MRI），对这种效应进行了深入研究。由于缺乏腺泡形态的现实几何模型，几何结构与信号衰减之间的关系仍然不明朗。在本文中，我们在一个现实的腺泡模型中使用受限扩散的蒙特卡罗模拟来计算扩散加权核磁共振实验中的信号衰减。我们证明，这种技术应该对分支结构的破坏敏感：肺泡间组织的部分去除会在树状腺泡结构中产生环路，从而增强扩散运动以及随之而来的信号衰减。本文还讨论了局部几何结构的作用及相关实际应用。
