Quantitative Measurements Of Iron Content In Liver Fibrosis Of Rats Using MRI

Objective:To explore the mri diagnostic value of quantitative measurements of iron content in liver fibrosis,which are liver-to-muscle SI ratio of mri with multi-echo and multi-sequence and T2 values.Materials and Methods:1.iron in vitro phantom of the MRI test:1.55L plastic bottled is filled with 1460ml distilled water and surrounding with sealed 1L distilled water bag made of the phantom.After each MRI scan the phantom,injected 150mg Fe/ml of iron dextran solution 1ml and shake very well to containing different concentrations of iron model,injection 40ml dextran solution.Philips Achieva3.0T,8-channel knee coil.Scanning sequence including M-GRASE respiratory triggering fast spin echo（turbo spin echo TSE）fat suppressed T2 weighted imaging（T2 weighted imaging and T2WI）and magnetic susceptibility weighted imaging（susceptibility-weighted imaging,SWI,Philips machine with clear Ven-BOLD-HR sequence for data acquisition）,T2^*-weighted imaging(T2^*-weighted imaging,T2^*WI,Philips machine with multi echo fast field echo（multiecho fast field echo,the sequence of M-FFE-short for data acquisition）,dual echo chemical shift（dual fast field echo,dual FFE）T1 weighted imaging(T1 weighted imaging（T1WI）,multi echo gradient spin echo(multi-echo gradient and spin echo sequence.Three radiologists measured and calculated the SIR,r SI,T2 values of the phantom,Analysis of the correlation of the iron concentration and the the SIR,r SI and T2 values so that establish the corresponding regression equation.The best correlation and the highest Goodness of Fit regression equation was selected.3.Quantitative measurements of liver iron content in live fibrosis rat model using MRI:49adult male Sprague–Dawley rats,weight（226±3.6g）,which were randomly divided into two groups:the control group（n=7）with saline by subcutaneous injection（0.3 ml/100 g）,twice a week,while the experimental group（n=42）with40%ccl4 solution by subcutaneous or intraperitoneal injection（0.3 ml/100 g）.injected a total of 12 weeks.After 6 weeks,4 or 5 rats were selected of experimental groups and 1 rat was selected of control group were performed MRI scan every week.After that rats were decollated quickly and the liver were dissected out and put into normal saline solution to remove the blood.then immersed in 10%fixed in neutral formaldehyde fixative for 12 hours to hematoxylin&eosin（HE）for routine examination,Masson staining for collagen,and Prussian blue for iron.HE and Masson staining evaluated The degree of liver injury and fibrosis,Prussian blue staining was used to detect liver iron deposition in the progression of liver fibrosis.three radiologists measured SD rats Liver-to-muscle SI ratio,T2 and R2 values.assess the correlation of the Liver-to-muscle SI ratio,T2 and R2 values with the stage of liver inflammation and fibrosis.select a significant correlations to comparative with the equation which is established to the iron in vitro phantom and also have a significant correlations with iron content.iron content can be calculated.Analysis the correlation of SIR and liver inflammation and fibrosis and liver iron content.4.the reliability of MRI quantitative study of hepatic fibrosis of liver iron content:10 rats which was selected in the experimental group perfromed SWI examinations and after an interval of 30 minutes to repeat the same sequence scanning,three radiologists measured and calculated the SIR value of the first and second scanning sequence and take the average value for the last.Using a paired t-test and intraclass correlation to compares the means for the SIR value.5.SPSS17.0 statistical software package is used for data processing and analysis.Statistical analysis Data were expressed as mean±standard deviation,range and median.the difference was statistically significant（P<0.05）.result:1.iron in vitro phantom of the MRI test:three radiologists measured and calculated the SIR value of the T2WI,SWI,T2^*WI,the r SI value of T1WI and the T2 values of M-GRASE sequences and take the average value for the last.They range from（0.0027～1.1994）,（0.0233～1.4405）,（0.0085～1.8203）,（0.0082～0.3278）,（-2.0000～2047.0000）respectively.Median was 0.0082,0.1869,0.2044,19.8000 respectively.The correlation coefficients which between the SIR,r SI and T2 values and the concentrations of iron mould were(r_T2WI=-0.789,P=0.000),(r_SWI=-0.997,P=0.000),(r_T2*WI=-0.878,P=0.000),(r_{r SI}=0.942,P=0.000),(r_T2=-0.969,P=0.000)r espectively.the SIR of T₂WI,T₂^*WI and SWI sequence with different iron concentration of phantom are respectively established the compound regression equation Y=0.038×（0.541）^t（Y:the SIR values measured by T2WI sequence of the phantom,t:iron concentration of the phantom）,Y=1.368×0.260（Y:the SIR values measured by SWI sequence of the phantom,t:iron concentration of the phantom）,Y=1.182×0.374^X（Y:the SIR values measured by T₂^*WI sequence of the phantom,t:iron concentration of the phantom）.R² of the equation was 0.475,0.990,0.988 respectively.The r SI and T2 values with different iron concentration of phantom are established the linear regression equation:Y=0.045+0.074X（Y:the r SI values measured by T1WI sequence of the phantom,t:iron concentration of the phantom）,Y=46.103-15.347X（Y:the T2 values measured by the T2 map which is construction from 4 echo M-GRASE sequence,t:iron concentration of the phantom）.R² of the equation was 0.887、0.939 respectively.2.Quantitative measurements of liver iron content in live fibrosis rat model using MRI:49 adult male Sprague–Dawley rats,control group（n=7）there were no death.experimental group（n=42）there were 14 deaths during the modeling,The death rate is about 33.3%.which were divided into stage 0（S0）group（n=9）,stage 1（S1）group（n=6）,stage 2（S2）group（n=7）,stage 3（S3）group（n=6）,and stage 4（S4）group（n=7）according to their histopathological stage of liver fibrosis.three radiologists measured and calculated the SIR value of the SWI sequences and take the average value for the last.There was a positive correlation between the iron content of liver and the degree of hepatic fibrosis（r=0.951,P=0.000）,and there had statistic Significance between the hepatic fibrosis and the liver iron concentrition.（P<0.05）.3.the reliability of MRI quantitative study of hepatic fibrosis of liver iron content:three radiologists measurement and calculation the SIR values of the first and second SWI sequence and take the average value for the last.the SIR values of 10 SD rats which was selected of the experimental group rats was0.856558+0.059678,0.864447+0.078341.paired t test and the ICC value of them were not statistically significant（t=-0.416,P=0.687）,0.997（F=696.013,P=0.000）.Conclusion:1.The SIR of T2WI,SWI,T₂^*WI,the r SI values of T1WI and T2 value are correlation with iron content in the vitro phantom.the SIR value of the SWI,T2 value is significantly negatively correlated with the iron concentration of the vitro phantom.The r SI value is significantly positively correlated to the iron concentration of the vitro phantom.the curve-composite equation of which was constructed between the SIR value of the SWI and the content of the vitro phantom is highest goodness of fit（R²=0.990）.2.When the iron content in the vitro phantom is greater than or equal to 2.4590mg Fe/ml,PHILLIP3.0T MRI cannot measure the T2 value.3.The SIR of is negatively correlated with the stege of rat liver fibrosis.there is a significantly positive correlation between the stage of liver fibrosis and liver iron conten.liver iron content increasing the stage of liver fibrosis.the stege of rat liver fibrosis was positively correlated with the liver iron concentration,increasingly with the stage of hepatic fibrosis,and they have statistically significant.4.Quantitative measurements of iron content in liver fibrosis using MRI is reliable.