7.0 T高场磁共振磁敏感倍增成像效应研究

The Study of the Blooming Effect in High-Field MRI at 7 T

磁敏感性可以看作是物质的一种固有属性,不同的组织由于成分与结构的差异,磁敏感性往往各不相同,有效地利用磁化率的差异可为组织结构与功能提供额外的信息。基于这种新的成像对比机制,磁敏感加权成像技术(SWI)诞生。研究发现,在一定的条件下,由于磁敏感性差异的存在,特定组织在MR成像过程中会出现"成像倍增",这种现象被称为磁敏感倍增成像效应。作为SWI技术的研究基础,全面准确地评估磁敏感倍增成像效应对SWI技术在临床上的进一步应用有重要意义。开展磁敏感倍增成像效应的相关研究,结合计算机模拟与体外实验,以像素数量及倍增因子为评估指标,建立磁化率、回波时间及物理大小与磁敏感倍增成像效应之间的量化关系。计算机模拟实验结果显示,磁化率、回波时间与磁敏感倍增成像效应呈正相关,在实验范围内,幅值与相位得到的倍增因子最高可达37,而在半径为0.5 voxel的圆柱模型中,SWI数据得到的倍增因子最高可达51;体外实验结果显示,0.3和0.46mm为直径的圆柱模型的倍增因子最高分别为13.25以及10.75,模型半径越小,磁敏感倍增成像效应越明显。研究结果对于SWI成像技术的发展以及疾病的早期发现有重要的参考价值。

Magnetic susceptibility can be regarded as an intrinsic property of matter. Different tissues tend to have different magnetic susceptibility due to the differences in composition and structure. Effectively uses of the magnetic susceptibility may provide additional information of the structure and function of the organization.Based on this new imaging contrast mechanism,Susceptibility-weighted imaging emerged. There were some studies that have found that specific tissues could be extended under certain conditions due to the difference in magnetic susceptibility,which was called the blooming effect. As the basis,a comprehensive and accurate assessment of the blooming effect was important for the further application of SWI in clinical. In this paper,the related research of blooming effect was carried out systematically. Combined the silico and the ex-vivo experiment,we built the relationship between the susceptibility,echo times and size with the blooming effect using the number of the pixels and the blooming factor as the evaluation indexes. The silico result showed that,the susceptibility and echo times were positively correlated with the blooming effect. In this experiment,the magnitude and phase blooming factor could be up to 37. But in the model with 0. 5 voxel radius,the blooming factor obtained by SWI could be up to 51. In addition,the results of ex-vitro experiments showed that the blooming factor in the diameter of 0. 3 mm and 0. 46 mm models could be up to 13. 25 and 10. 75 respectively.So that the smaller the radius of the model,the more obvious the blooming effect could be. The results of this research has important reference value to promote the development of SWI and early detection of diseases.