Objective To investigate the diagnostic efficacy of mDixon histogram parameters in distinguishing grade of primary lymphedema of lower extremity.Methods Seventy-four patients with primary lymphedema of lower extremity,21 cases were mild(Ⅰ degree),18 cases were moderate(Ⅱ degree),35 cases were severe(Ⅲ degree).In the mDixon im-age of the patient,the subcutaneously and intramuscular area of the edema was filled with the semi-automatic threshold method in ITK-snap software,the doctor erases the tissue out of the region layer by layer and generates the region of interest(VOI).Parameters of VOI were extracted by FAE software:percentile(10％,90％),maximum,minimum,mean,range,skewness,root mean square difference,kurtosis,variance.One-way ANOVA and nonparametric tests were used for analysis of differences between groups,with pairwise comparisons using the LSD method and all paired methods.Receiver operating characteristic(ROC)curves were used to identify and calculate the diagnostic efficacy of statistically significant parameters between groups for mild and non-mild,severe and non-severe sensitivity and specificity.Results In the histogram pa-rameters of Ⅰ degree,Ⅱ degree and Ⅲ degree patients:percentile(10％,90％),maximum,minimum,mean,range,skewness,root mean square difference,the differences among the three groups were statistically significant.There was no significant difference in peak degree and variance among the three groups.The parameters with statistical difference among the three groups were selected for ROC analysis.The AUC of the 10th percentile was 0.74,the 95％confidence interval was 0.62-0.87,the sensitivity was 54.7％,and the specificity was 90.5％.The sensitivity of 90th percentile and root mean square was 73.6％.The parameters with significant difference among the three groups were selected for ROC analysis.The AUC of the 10th percentile was 0.86,95％confidence interval was 0.77-0.95,the sensitivity was 71.4％,and the specificity was 92.3％.The highest value and range specificity were 94.9％,and the highest value,root mean square value and skewness sensitivity were 85.7％.Conclusion mDixon histogram parameters are useful in the diagnosis of primary lymphedema of lower extremity.
Primary lymphedema of lower extremityMagnetic resonance imagingHistograms
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