1.School of Biomedical Engineering,Shanghai Jiao Tong University;2.Department of Radiology, School of Medicine, Shanghai Jiao Tong University
铁元素和髓鞘的变化间接反映了大脑结构与功能的改变，并与多种神经退行性疾病相关。在脑发育及老化过程中，铁元素沉积和髓鞘形成与脱落的过程会引起脑组织磁化率数值的改变。定量磁化率成像（Quantitative Susceptibility Mapping，QSM）是一种基于梯度回波（Gradient Recalled Echo，GRE）序列对磁化率进行定量的磁共振成像手段，可定量脑灰质中铁元素的沉积和脑白质中髓鞘的含量。有研究表明，可以基于 QSM 图像用指数和泊松函数拟合脑发育过程中铁元素与髓鞘的发展轨迹，得到与组织学等其他定量手段相似的结论。在此基础上，研究人员构建了基于 QSM 图像的全年龄脑图谱，为研究铁元素和髓鞘在脑老化及神经退行性疾病中的作用提供了基础。该文介绍了 QSM 成像原理及其在脑发育及老化定量研究中的最新进展。
Changes of iron and myelin content in the brain can indirectly indicate alterations in brain function and are often associated with various neurodegenerative diseases. The processes of iron deposition and myelination/demyelination are known to occur during brain development and aging, and are often accompanied by changes in susceptibility of brain tissue. One method for quantifying such changes is Quantitative Susceptibility Mapping (QSM), which is a magnetic resonance imaging technique based on Gradient-Recalled Echo (GRE) sequences to measure tissue susceptibility. QSM can be used to quantify the deposition of iron in the gray matter and myelination/demyelination in the white matter. The trajectory of iron and myelin during brain development can be modeled using exponential and poisson functions based on QSM images, which can yield results consistent with other quantitative tools such as histological quantification. Based on this methodology, researchers have constructed a longitudinal atlas from QSM images, which provides a basis for exploring the role of iron and myelin in brain aging and neurodegenerative diseases. In this review, we first introduce the principle of QSM and its applications to the studies of brain development and aging.