Biomedical Engineering Department, Pratt School of Engineering, Duke University, 136 Hudson Hall, Durham, NC 27708, USA.
Neuroimage. 2010 Oct 15;53(1):132-8. doi: 10.1016/j.neuroimage.2010.06.019. Epub 2010 Jun 16.
In this study we describe our development and implementation of a magnetization transfer (MT) prepared stimulated-echo diffusion tensor imaging (DTI) technique that can be made sensitive to the microanatomy of myelin tissue. The short echo time (TE) enabled by the stimulated-echo acquisition preserves significant signal from the short T(2) component (myelin water), and the MT preparation further provides differentiating sensitization to this signal. It was found that this combined strategy could provide sufficient sensitivity in our first attempt to image myelin microstructure. Compared to the diffusion tensor derived from the conventional DTI technique, the myelin water weighted (MWW) tensor has the same principal diffusion direction but exhibits a significant increase in fractional anisotropy (FA), which is mainly due to a decrease in radial diffusivity. These findings are consistent with the microstructural organization of the myelin sheaths that wrap around the axons in the white matter and therefore hinder radial diffusion. Given that many white matter diseases (e.g. multiple sclerosis) begin with a degradation of myelin microanatomy but not a loss of myelin content (e.g. loosening of the myelin sheaths), our newly implemented MWW DTI has the potential to lead to improved assessment of myelin pathology and early detection of demyelination.
在本研究中，我们描述了一种磁化传递（MT）准备的激发回波扩散张量成像（DTI）技术的开发和实现，该技术可以对髓鞘组织的微观结构敏感。激发回波采集所允许的短回波时间（TE）保留了来自短 T2 成分（髓鞘水）的显著信号，而 MT 准备进一步提供了对此信号的区分敏感。结果发现，这种组合策略可以在我们首次尝试成像髓鞘微观结构时提供足够的灵敏度。与传统 DTI 技术得出的扩散张量相比，髓鞘水加权（MWW）张量具有相同的主扩散方向，但各向异性分数（FA）显著增加，这主要是由于径向扩散率降低所致。这些发现与髓鞘鞘围绕白质中的轴突的微观结构组织一致，因此阻碍了径向扩散。鉴于许多白质疾病（例如多发性硬化症）始于髓鞘微观结构的退化而不是髓鞘含量的丧失（例如髓鞘鞘的松动），我们新实施的 MWW DTI 有可能改善髓鞘病理评估和脱髓鞘的早期检测。
