| Background With a high worldwide prevalence,NAFLD is recognized as the most common cause of chronic liver diseases.Accurate quantification of liver fat and iron content has great significance in clinical classification and pathogenesis exploration of NAFLD.Liver biopsy remains the reference standard for hepatic steatosis and iron deposition diagnosis.However it is limited by its invasiveness,sampling bias and inter-observer diagnostic variability.Therefore noninvasive methods are needed to detect and quantify hepatic steatosis and iron deposition as an alternative to liver biopsy especially in the follow-up of NAFLD patients.Technological advancements have pushed MR to new frontiers of medical application.Objective Combined customized lipid phantom with rabbit NAFLD model,to investigate the value of MRI IDEAL-IQ technology in quantification of fat and iron content.And applied to clinical practice,to evaluate liver fat content changes before and after mesenchymal stem cell infusion therapy of type 2 diabetes patients,to explore the value of its clinical application.Methods(1)Four groups(A、B、C、D)of phantoms(20ml)were constructed,each of which is composed of eight homogeneous fat-water phantoms with fat volume ratio at 0%,5%,20%,35%,50%,65%,80%and 95%respectively.Phantoms of group B were added with 0.05mg magnetic microspheres(Main components:Fe3O4),and group C with O.lmg,group D with 0.15mg.All phantoms had undergone MR examination with IDEAL-IQ technology.The MR images were processed on workstation(AW Volume Share 4;GE Healthcare)to measure the MRI-PDFF values on fat fraction maps.One-way ANOVA and Pearson correlation test were used for statistical analysis.(2)R2*values were measured on R2*maps reconstructed from IDEAL-IQ technology.For statistical analysis,one-way ANOVA,SNK-Q test and Pearson correlation test were applied.(3)This animal experiment was performed with approval of the institutional animal care and use committee.Forty rabbits were randomly divided into four groups with different diets and raising periods.MRI examinations were performed with IDEAL-IQ on a 3-T MR imaging unit.Liver PDFF and R2*relaxometry calculations were performed on fat fraction and R2*maps.Liver samples were stained with hematoxylin-eosin(HE)and Oil red O to evaluate the degree of hepatic steatosis,Prussian Blue to evaluate the degree of liver iron content.The histopathology results of liver fat was calculated by ratio of fatty content in liver to liver volume(VP value)using image pattern analyzer.Kruskal Wallis test and Pearson correlation coefficient were used for statistical analysis.(4)We recruited T2MD patients participated in clinical trials in PLA General Hospital from Aug.6th,2015.IDEAL-IQ technology was employed to evaluate liver fat content changes before and after mesenchymal stem cell infusion therapy,to explore the value of its clinical application,and to observe the liver fat content change trend.Results(1)Evaluated MRI-PDFFs of four groups acquired by IDEAL-IQ have no significant difference with the true fat contents(F value 0.011,p value 1.0).The existence of magnetic microspheres did not affect measurement accuracy of IDEAL-IQ.Close correlation between MRI-PDFFs of each group and true fat contents were observed(r values were 0.998,0.998,0.999,0.998).(2)Mean R2*relaxometrys of the four phantom groups were 28.77 ± 14.62,71.37±35.00,108.08±24.38,144.22±41.86.R2*values showed significant differences between each two groups,while no correlation between R2*and iron level.(3)A total of 37 rabbits were included in this study.At histological analysis of the rabbits,livers were categorized by steatosis severity as normal,mild,moderate and severe.MRI-PDFF was significantly higher in rabbits with NAFLD than those with a normal liver.MRI-PDFF and VP showed significant differences between normal and NAFLD groups,whereas this was not observed in R2*relaxometry.Close correlation between MRI-PDFF and histological steatosis was observed(r =0.78,p<0.01).Hepatic iron deposit was not found in any rabbits from Prussian Blue staining results.And no correlation between either liver MRI-PDFF or histological steatosis and R2*was observed.(4)A total of 9 cases of patients T2MD were included in this clinical collection,5 males,4 females,with an average age of 49 years old.The average collection period was 138.4 days,and mean MRI-PDFF values before and after the treatment were 7.61±4.30%、6.80±3.72%.And MRI-PDFF did not show significant differences before and after the treatment(p = 0.672).Conclusion:Fat-water Phantoms and rabbit NAFLD model have confirmed quantification feasibility and accuracy of IDEAL-IQ of fat research.R2*measurement and classification for iron deposition need further experimental investigaton.MRI-PDFF created from IDEAL-IQ provided a noninvasive,accurate estimation of hepatic fat deposition in rabbits with NAFLD,and should be considered as a new reference standard.The relationship of iron deposition and NAFLD needs to be further explored.The continuous development of MRI technologies,particularly the accomplishment of IDEAL-IQ measuring MRI-PDFF and R2*simultaneously,has provided prominent measures for diagnosis and quantification of steatosis and iron deposition,especially for the NAFLD patients who need long-term clinical follow-up and observations.However,the evaluations of the reliability and accuracy of the technology are still critical in order to determine whether they can be used to substitute histological examination as the gold standard to assess NAFLD hepatic steatosis and iron deposition. |
