Six-echo Dixon And Histo Technique To Quantify The Vertebral Bone Marrow Fat Content In Rabbit Model Under Iron Overload

Objective: 1.By establishing a rabbit model of lumbar iron overload,the accuracy of Qdixon and Histo techniques in quantifying fat fraction(FF)in the condition of iron overload was discussed.2.To compare the difference and correlation of Qdixon and Histo in the quantitative bone marrow fat content.Materials and methods: Sixteen rabbits were randomly divided into experimental group and control group(8 rabbits and 8 rabbits).The 8experimental groups were injected with dextran iron(30mg/kg)once a week into the hind leg muscle of rabbits,while the control group was not injected with iron.One week after iron injection,1 experimental group and 1 control group were randomly selected for lumbar MRI scanning,which included routine spin echo pulse sequence,Qdixon,Histo sequence scanning.One ml of Serum Iron(SI)was taken from the two groups of rabbits upon examination of the anterior auricular vein.The 5th and 6th lumbar vertebrae were dissected for pathological examination.The remaining lumbar vertebrae were sent to Guangxi Analysis and Test Research Center to measure the iron content and bone marrow fat content.MR scanning and autopsy were performed on 8 rabbits in the control group and the experimental group at the same time point.The experiment lasted eight weeks.SPSS20.0 software was used for analysis,and W test(national standard GB4880-85)was used for measurement of normality.Two independent samples with normal distribution and homogeneous variance were tested by t-sample T-test,and the differences between the experimental group and the control group were compared by Qdixon and Histo sequence measurements.Pearson or Spearman correlation analysis: 1.The relationship between serum iron,bone marrow iron content,liver iron concentration and total injected iron;2.2.The relationship between the lumbar bone marrow fat fraction measured by Qdixon sequence 5 and 6 and the corresponding lumbar bone marrow fat fraction measured by Histo;3.Correlation between bone marrow fat content,bone marrow fat percentage and fat fraction determined by Qdixon and Histo by atomic spectrophotometer.The test standard was P=0.05,P<The difference was statistically significant(0.05).Result:The total amount of injected iron was highly positively correlated with the iron content in the bone marrow(R =0.976,P < 0.001),the total amount of injected iron was highly positively correlated with the iron concentration in the liver(r=0.901,P =0.002),and the iron concentration in the bone marrow was highly positively correlated with the iron concentration in the liver(r=0.934,P=0.001).There was no correlation between total iron injection and SI(R =0.592,P =0.120).There was no difference between the control group and the experimental group(T =-1.895,P =0.088)in the fat score of the 5th lumbar spine bone marrow,and there was a difference between the 6th fat score(T=-2.559,P =0.023).No difference was found between the control group and the experimental group(T =-0.983,P =0.342,T =-482,P =0.637).The lumbar fat scores of the 5 and 6 lumbar vertebrates measured by Qdixon sequence were moderately positively correlated with those measured by Histo sequence(r=0.577,P =0.019,r=0.555,P =0.026).By atomic spectrophotometer instrument measurement of bone marrow fat content and Qdixon,Histo fat score no linear correlation(r = 0.369,p = 0.176,r = 0.029,p = 0.918),bone marrow fat percentage and Qdixon determination of lumbar vertebral bone marrow fat score no linear correlation(r = 0.103,p = 0.726,r = 0.067,p = 0.813),bone marrow fat percentage lumbar vertebral bone marrow fat scores were positively correlated with the measurement with Histo(r = 0.722,p = 0.002,r = 0.601,P =0.018).There was no correlation between bone marrow fat content measured by atomic spectrophotometer and bone marrow fat percentage in lumbar spine pathology(r=0.164,P =0.560).Conclusion: 1.The rabbit lumbar spinal bone marrow iron overload model could be established by injecting dextran iron into the hind leg muscle;2.Histo sequence can accurately quantify the bone marrow fat content of lumbar vertebrae 5 and 6 under iron overload in rabbits.3.The bone marrow fat fraction measured by Qdixon sequence was positively correlated with the bone marrow fat fraction measured by Histo sequence.4.It is still uncertain that Qdixon sequence can accurately quantify the lumbar bone marrow fat content under the condition of iron overload in rabbits.