MRI化学位移同、反相位成像的体外实验模型研究

MR Chemical-shift In-phased and Opposed-phased Imaging: An Experimental Study with Phantom

目的 通过建立同、反相位的体外实验模型,探讨与同相位相比,反相位上信号强度变化与脂肪含量的相关性,并从中确定反相位上信号强度明显下降时的确切脂肪含量的标准。材料与方法 模型建立方法:将1％琼脂糖水溶液与色拉油先后倒入一长方形水槽内,在水-脂交界处采用层厚10mm倾斜面进行同、反相位检查。测出同、反相位图像各部感兴趣区(ROI)的信号强度(SI),计算信号强度下降指数(SI指数)值,并且绘制脂肪含量与SI指数关系的曲线图。结果 最初脂肪比例较低时,随脂肪含量增加,反相位的信号强度呈逐渐下降表现;而当脂肪比例较高时,其信号强度随着脂肪含量的增加而升高,其反转点的脂肪含量为23％。结论 脂肪含量在23％左右时,反相位上的信号强度有较为明显的下降,而且脂肪含量愈接近该值,信号强度下降的程度就愈明显。

Objective To establish fat-water chemical-shift in- and opposed-phased imaging phantom, to discuss the relationship between the lipid fraction and the signal intensity index, and to determine the proportion of fat content at the point of which the relationship or signal intensity on opposed-phased image with fat content became reversed. Materials and Methods The phantom was filled with 1% agarose and salad oil. Using FMSPGR sequence, the in- and opposed-phase imaging with 10 mm oblique slice was performed at the fat-water interface, which slid along from left to right. Signal intensity at different ROIs on both in- and opposed-phase image was estimated. Results When the fat content proportion was low (within 0 ~ 23% ), the signal intensity on opposed-phased images showed a negative correlation with the fat content. Conversely, the signal intensity on opposed-phased images increased with the fat content when the fat content proportion was over 23% . The reversed point occurred at the content of fat being 23% . Conclusion The signal intensity on opposed-phased images decreases with the fat content until the fat content reaches to 23% , while the signal intensity on opposed-phased images increases with the fat content when the fat content is over 23 % .