| Part1Quantitative assessment of different iron concentration in vitro model:a comparative study between1.5T and3.0T MRObjective:To investigate the feasibility of quantitative assessment of iron concentration in vitro model using MRI and compare the accuracy between1.5T and3.0T MR.Materials and Methods:Two sets of iron concentration in vitro models, ranging from0mg/ml to5.0mg/ml and from0mg/ml to1.00mg/ml, respectively. The two sets models were performed both on1.5T and3.0T MR in the same day. The scanning protocol included FSE/T1WI, FRFSE/T2WI, T2map and T2*map on axial section, and scanning range were from top to bottle of the solution. Two radiologists independently evaluated the MR images of the models.T1WI signal to noise ratio (SNR), T2WI SNR, T2, R2, T2*and R2*values were measured. Intraclass correlation coefficient (ICC) was used to evaluate the agreements of the parameters and Pearson correlation analysis was used to calculate the correlation between iron concentration and MR measurement indexes.Results:The ICCs of T1WI SNR, T2WI SNR, T2, R2, T2*and R2*values evaluated by two radiologists were all more than0.900(P<0.001). The relation between iron concentration and T2WI SNR, T2and T2*values demonstrated function relation. When iron concentration was less than1.5mg/ml, T1WI SNR and R2correlated positively with iron concentration in1.5T MR(P<0.05); while iron concentration was more than1.5mg/ml, T1WI SNR and R2correlated negatively with it(P<0.05). When iron concentration was less than2.5mg/ml, R2*had a positive correlation with it (P<0.001); while more than 2.5mg/ml, R2*had a negative correlation with it (P=0.008).When iron concentration was less than1.5mg/ml, T1WI SNR had no significant correlation with it(P=0.301) in3.0T MR; while iron concentration was more than1.5mg/ml, T1WI SNR had a significantly positive correlation with it(P=0.001). When iron concentration was less than0.900mg/ml, R2and R2*were positively correlated with it(P<0.05); while it was more than0.900mg/ml, R2and R2*were negatively correlated with it(P<0.05).Conclusion:MRI is able to quantitatively evaluate iron concentration in vitro model accurately, reproducibly and stably, and it is better on1.5T MR. Part2Quantitative assessment of myocardial iron overload rabbit model by MRIObjective:To discuss whether it is feasible for magnetic resonance T2*map to evaluate myocardial iron concentration of myocardial iron overload rabbit model.Materials and Methods:Eleven rabbits were divided into two groups, myocardial iron overload group (n=10) and control group (n=1). Iron dextrin (concentration of50mg/ml, dose of50mg/kg) was injected in muscles of thigh once a week, totally12weeks. Before iron dextrin ejection, all the11rabbits were performed MRI. The myocardial iron overload group underwent MRI1week after iron dextrin injection. MRI scanning protocol included cardiac short axial Double inversion recovery-FSE (DIR), Triple inversion recovery-FSE (TIR) and T2*map, as well as liver and kidneys FSPGR/T1WI, SSFSE/T2WI and T2*map on axial section. Myocardial to erector spinae signal intensity ratio, liver to erector spinae signal intensity ratio, kidney to erector spinae signal intensity ratio, as well as T2*and R2*of myocardial, liver, kidney and erector spinae were evaluated. After animal models killed, heart, liver and kidneys were fixed in order to undergo MRI and excise for pathological slices. All rabbits were withdrawn blood to test serum iron, one day before performed MRI. Pearson correlation analysis was used to evaluate relations among measurement indexes.Results:Myocardial T2*, R2*values and DIR myocardial to erector spinae signal intensity ratio had linear correlation with injecting iron content(P<0.05), while TIR myocardial to erector spinae signal intensity ratio had no significant correlation with injecting iron content. Myocardial T2*and R2*values had no significant correlation with liver T2*and R2*values(P<0.05). Liver T2*and R2*values were not significantly correlated with injecting iron content(P>0.05). Kidney T2*, R2*had significant correlation with injecting iron content(P<0.001),while TIWI and T2WI kidney to erector spinae signal intensity ratio had no significant correlation(P>0.05). MR measurement indexes were not significantly correlated with serum iron(P>0.05). T2*and R2*of heart and kidney in vitro had linear correlation with injecting iron content(P<0.05), while T2*and R2*of liver had no significant correlation with injecting iron content(P>0.05). The change of myocardial T2*value was consistent with myocardial pathological resultsConclusion:MR T2*map is able to evaluate myocardial iron concentration of myocardial overload rabbit model accurately, and to provide a simple, safe, noninvasive and complete modality for iron load diagnosis and follow-up supervision. Part3Assessment of cardiac function with myocardial iron overload:a rabbit model MR studyObjective:To determine the relationship between cardiac function parameters and myocardial iron load of myocardial iron overload rabbit model, and the relationship between cardiac function and hepatic iron concentration.Materials and Methods:Eleven rabbits were divided into two groups, myocardial iron overload group (n=10) and control group (n=1). Iron dextrin (concentration of50mg/ml, dose of50mg/kg) was injected in muscles of thigh once a week, totally12weeks. Before iron dextrin ejection, all the11rabbits were performed MRI. The myocardial iron overload group underwent MRI1week after iron dextrin injection. MR scanning protocol included cardiac short axial cine, Double inversion recovery-FSE (DIR), Triple inversion recovery-FSE (TIR) and T2*map, as well as liver FSPGR/T1WI,SSFSE/T2WI and T2*map on axial section. Cardiac function parameters, myocardial to erector spinae signal intensity ratio and liver to erector spinae signal intensity ratio, as well as T2*and R2*of myocardial, liver and erector spinae were evaluated. After animal models killed, heart and liver were fixed to excise for pathological slices. All rabbits were withdrawn blood to test serum iron, one day before performed MR. Pearson correlation analysis was used to evaluate relations among cardiac function indexes, injecting iron content, serum iron and T2*map measurement indexes.Results:LVEDD, LVEDV, LVESV and LVEF had significant linear correlation with injecting iron content(P<0.05) and LVSV as well as LVCO has moderate correlation with serum iron(P<0.05). RVEDV, RVESV and RVEF were correlated with injecting iron content significantly(P<0.05), as well as RVEDV and RVESV were correlated with serum iron significantly(P<0.05). LVESD, LVEDV, LVESV and LVEF had a significant linear correlation with myocardial T2*, as well as LVEDD, LVESD, LVEDV, LVESV and LVSV had a linear correlation with myocardial R2*(P<0.05). RVEDV and RVESV were moderate correlated with myocardial T2*and R2*(P<0.05).Cardiac function parameters had no significant correlation with liver T2*and R2*(P>0.05).Conclusion:MRI is a simple, convenient, complete and effective modality to evaluate iron load in vivo, and can evaluate cardiac function simultaneously. LVESV may be better than LVEF to predict cardiac function of myocardial iron overload. Part4Clinical application of MR-T2*evaluating myocardial iron overloadObjective:To evaluate myocardial load of patients with iron overload by MR T2*map, and relationship with their cardiac function.Materials and Methods:Eight patients with iron overload (iron overload group) were enrolled in this study from October2010through October2012. The control group were healthy volunteers (n=22). Iron overload group and control group both underwent the examination in1.5T MR scanner. The MR protocol included short axial cine, T2*map of left ventricle and axial T2*map of abdomen. Two radiologists independently measured all the MR images. Cardiac function parameters, T2*and R2*values of left ventricle16segments, as well as T2*and R2*values of liver, pancreas, spleen and erector spinae were measured. The agreements of two radiologists were evaluate by intraclass correlation coefficient (ICC). The differences between iron overload group and control group were calculated by independent sample t-test, as well as relationship between T2*values of myocardial and liver and cardiac function parameters were calculated by Pearson correlation analysis.Results:The ICCs of T2*and R2*of myocardial, liver, pancreas, spleen and erector spinae and cardiac function parameters measured by two radiologists were all more than0.900(P<0.001). Four iron overload patient with myocardial iron overload, and T2*values of30myocardial segments were less than20ms. Of eight patients with iron overload, seven cases had hepatic iron overload and five cases had spleen iron overload. T2*values of liver and spleen between iron overload group and control group had significant differences (P<0.05). Pancreas and erector spinae had no iron overload in iron overload group. Left ventricle wall thickness, dimensions of right ventricle, stroke volume of chambers and ejection fraction were all within the reference ranges. Left ventricle end-systolic dimension was significantly larger than the control group one (P=0.005). End-diastolic dimension, end-systolic volume and end-diastolic volume were larger than the control group ones, but the differences had no significance (P>0.05). Left ventricle shortening fraction was in reference range, though it was significantly lower than the control group one (P=0.004). It had no significant correlations between myocardial T2*and hepatic T2*(P>0.05), and also no significant correlations between cardiac function parameters and T2*values of myocardium and liver(P>0.05).Conclusion:MR T2*is able to diagnose and supervise myocardial iron load promptly, reliably, sensitively and noninvasively. LVESD ad LVFS may substitute LVEF to predict cardiac function of patients with myocardial overload. |
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