磁共振-R_2~＊值无创评估铁过载肝脏铁含量的初步研究

The Experiment Study of MRI R_2~＊ Value for Noninvasive Measurement of Liver Iron Content in Iron Overload Rabbit

目的以病理学结果为对照,研究磁共振R2*成像定量评估铁过载家兔模型肝脏铁含量的可行性及R2*值与肝脏铁含量(LIC)之间的关系。材料与方法成年健康新西兰大白兔32只,随机分成4组,每组各8只(n=8)。A、B、C组每周注射一次铁剂,注射剂量分别为5、10、25 mg/kg体重,共4周。D组不予任何处理。应用MR扫描仪行肝脏的R2StarMap成像,经后处理生成R2*图,由一名经R2*Map成像后处理技术培训的放射科医师采用设置多个小的感兴趣区(ROI)求平均值法测得肝脏的R2*值。MR扫描结束后随即取兔肝作铁含量分析,得到LIC。采用Kruskal-Wallis Test分别对R2*值、肝组织铁含量各组之间的差异性进行分析,多重比较使用Tamhane’sT2法。采用两变量相关分析和曲线拟合分析R2*值和LIC之间的相关性。结果 (1)建模过程中,LIC随注射剂量增加而增加。(2)R2*值与LIC之间符合指数曲线关系,拟合的曲线回归方程为Y=EXP(1.950+16.200X),R=0.894。但当LIC>20.00 mgFe/g干重时,曲线的拟合度差,R仅为0.186。结论 R2*值能较好地反映兔肝脏铁浓度,并与组织学研究得到的肝铁含量呈明显的指数曲线相关。但当LIC较高(>20.00 mgFe/g干重)时,R2*值与LIC之间的相关性明显下降。

Objective To study the feasibility of MRI R2＊ for measurement of liver iron content（LIC） in iron overload rabbit compared with the pathological findings and laboratory data,and explore the relationship between R2 ＊ and LIC.Materials and Methods32 adult healthy New Zealand rabbits were randomly divided into four groups,group A（n=8）,group B（n=8）,group C（n=8） and control group（n=8）.Three iron overload groups received intravenous injection of iron sucrose of different dose every one week for four weeks.All experimental animals underwent liver scan with 2D MFGRE sequence by using GE Signa HDx 3.0 T MR.The R2＊ value were measured on R2＊ Map with small region of interest（ROI） methods by one observer who had been trained to use the technology proficiently.The liver of experimental animals were sent for LIC assessment immediately after MR scan.SPSS 13.0 for Windows statistical software was used to compare the relationship between R2＊ value with small ROI methods and LIC.Results（1）The LIC increased with the increased in total dose of iron.（2）There was a significant exponent curve association between the R2＊ value and LIC.Curve regression equation of the R2＊ value and LIC was Y=EXP（1.950＋ 16.200X）,R=0.894.A weak correlation（R=0.186） was displayed in animals with high LIC（above 20.0 mg/g dw）.ConclusionR2＊ value can accurately predict LIC with a significant exponent curve association,the correlation become weak with increased LIC（above 20.0 mg/g dw）.