Assaf Yaniv, Blumenfeld-Katzir Tamar, Yovel Yossi, Basser Peter J
Department of Neurobiology, the George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
Magn Reson Med. 2008 Jun;59(6):1347-54. doi: 10.1002/mrm.21577.
The diameter of a myelinated nerve axon is directly proportional to its conduction velocity, so the axon diameter distribution helps determine the channel capacity of nervous transmission along fascicles in the central (CNS) and peripheral nervous systems (PNS). Previously, this histological information could only be obtained using invasive tissue biopsies. Here we propose a new NMR-based approach that employs a model of water diffusion within "restricted" cylindrical axons to estimate their diameter distribution within a nerve bundle. This approach can be combined with MRI to furnish an estimate of the axon diameter distribution within each voxel. This method is validated by comparing the diameter distributions measured using the NMR and histological techniques on sciatic and optic nerve tissue specimens. The axon diameter distribution measured in each voxel of porcine spinal cord using MRI and using histological methods were similar. Applications are expected in longitudinal studies designed to follow nerve growth in normal and abnormal development, as well as in diagnosing disorders and diseases affecting specific populations of axons in the CNS and PNS.
有髓神经轴突的直径与其传导速度成正比，因此轴突直径分布有助于确定中枢神经系统（CNS）和周围神经系统（PNS）中沿束的神经传导通道容量。以前，这种组织学信息只能通过侵入性组织活检获得。在此，我们提出一种基于核磁共振（NMR）的新方法，该方法利用“受限”圆柱形轴突内的水扩散模型来估计神经束内轴突的直径分布。这种方法可以与磁共振成像（MRI）相结合，以提供每个体素内轴突直径分布的估计值。通过比较使用NMR和组织学技术在坐骨神经和视神经组织标本上测得的直径分布，验证了该方法。使用MRI和组织学方法在猪脊髓每个体素中测得的轴突直径分布相似。预计该方法可应用于旨在跟踪正常和异常发育中神经生长的纵向研究，以及诊断影响CNS和PNS中特定轴突群体的疾病和病症。
