SWI在脑内铁定量分析中的应用

Application of SWI in quantitative analysis of brain iron

目的利用SWI相位图来对脑内铁的分布和含量以及随年龄增长的变化趋势进行量化分析,并探讨SWI对脑内铁沉积显示的优势和不足。方法使用3.0T磁共振对62例健康者进行SWI成像分析脑内各部位相位图信号表现;按年龄段进行分组,观察随年龄变化各部位相位图信号变化特征。结果黑质(SN)、苍白球(GP)、壳核(Pu)、尾状核(CA)、运动皮层(MC)出现可观察的铁沉积所致信号减低较早(6～7岁),而红核(RN)和齿状核稍晚(9～10岁),内囊后支、视放射相对无明显信号减低;RN、SN、GP、Pu、CA、MC在20岁以前铁沉积较快,RN、SN、CA、MC在20～60岁之间铁沉积有个平台期。脑内铁的分布不均匀,GP和RN、CA、SN铁含量较高。结论 SWI相位图能够较好地反映脑内铁的沉积和分布,其成像基础为顺磁性的脑内铁蛋白会导致局部磁场改变从而使质子产生相对应的相位变化。

Objective To analyze the distribution and change of brain iron with age and to evaluate the advantage and disadvantage of this quantitative analysis method. Methods SWI on 3.0T MR scanner was performed on 62 healthy subjects, which were divided into 5 groups according to the age for analysis of the change of signal with age. Results In phase image of SWI, detectable signal loss was observed in substantia nigra （ SN）, globus pallidus （ GP）, putamen （Pu）, candate nucleus （CA） and motor cortex （MC） at earlier age （6 ~ 7 years）, while comparable later detection was revealed in red nucleus （RN） and dentate nucleus （9 -10 years）. Meanwhile, no signal loss was observed in posterior branch of internal capsule and optic radiation. An aggressive iron deposition was observed in RN, SN, GP, Pu, CA and MC before the age of 20, and a platform deposition reached afterward in RN, SN, CA, and MC. Prominent iron deposition was found in GP, RN, CA and SN. Conclusion SWI effectively presents the cerebral iron distribution and deposition. The foundation of SWI in brain iron quantitative analysis is that the paramagnetic ferritin causes the local magnetic field change, which produces corresponding phase change in phase image of SWI.