磁敏感加权脑静脉成像中的磁场不均匀性伪影滤除技术

Removing the Field Inhomogeneity Background Effects in the SWI Based Brain Venography

针对磁敏感加权法(SWI)在脑静脉成像中存在高频磁场不均匀性伪影的问题,提出一种新的基于伪影滤除技术的磁敏感加权法(BER-SWI)。在原始SWI的窗函数法将低频的磁场不均匀性伪影滤除的基础上,将图像按像素值分为特定的区段,通过区域平均边界差,检测出发生2π跳变的伪影区域,再用区域生长法完全生长出此区域的伪影,并将其滤除。结果表明,BER-SWI很好地解决了原始SWI无法去除颅底部的高频磁场不均匀性伪影的问题,得到了更加准确、清晰的磁敏感加权图。

To the problem of background effects caused by the high frequency field inhomogeneity existing in the original susceptibility weighted imaging （SWI）, this paper introduced a revised method named as background-effects-removing susceptibility weighted imaging （BER-SWI）. On the basis of removing the low frequency field inhomogeneities using the window function in the original SWI,the new method employed several steps to achieve a better result. Firstly,the image was divided into specified regions according to the values of the pixels. Then, the average region boundary differences were used to detect the regions of the background effects with the phase jump of 2π. Finally the region grow method was utilized to find out all the background effects regions for removing. The results demonstrated that BER-SWI could remarkably remove the background effects caused by the high frequency field inhomogeneity near the bottom area of the skull, producing more accurate and clearer susceptibility weighted images.