The Value Of QSM In The Diagnosis Of Mild Cognitive Impairment In Occupational Aluminum Workers

Objective:Using quantitative susceptibility mapping（QSM）to measure the susceptibility values of brain regions of occupational aluminum（Al）workers and investigating the application value of QSM in diagnosing mild cognitive impairment（MCI）.Methods:Analyzing the basic clinical data of 53 workers in an Al factory in Shanxi collected from October 2014 to November 2019.All workers underwent the Montreal Cognitive Assessment（Mo CA）Scale,and then divided into MCI group（28 cases）and normal control group（NC group,25 cases）according to their scores.All of them were further tested for blood Al concentration,conventional MRI,3D-T1WI and QSM scan.Using the3D-T1WI and T2 FLAIR as reference images,selected the region of interest（ROI）in the corresponding position of QSM images and measured value.The ROIs include bilateral caudate nucleus,putamen,globus pallidus,thalamus,hippocampus,red nucleus,substantia nigra,the dentate nucleus,the genu of corpus callosum,the splenium of corpus callosum,the cingulate gyrus,frontal white matter,parietal white matter,temporal white matter.The data obtained were tested for normal distribution and homogeneity of variances,which were in line with normal distribution and had uniform variances,two independent sample t-tests were used to compare the parameters between groups.Otherwise,non-parametric test was used to conduct statistical analysis of QSM values between the two groups.Spearman correlation analysis of statistically significant parameters was performed with Mo CA scores and serum Al concentration,respectively.The receiver operating characteristic（ROC）curve was used to assess differential diagnostic efficacy of statistically significant parameter in differentiating MCI from NC.The z-score test was used to compare the difference in area under the curve（AUC）.Results:1.Clinical characteristics:There was no difference in age and educational level（P>0.05）.The serum Al concentration of MCI group was higher than that of NC group,the difference was close to statistical significance（P=0.057）.2.Comparison of QSM values:The QSM values of left hippocampus(14.9837±2.8998 ppb(×10^-9)),left dentate nucleus(106.6973±5.6930 ppb(×10^-9)),right substantia nigra(143.6128±6.6035 ppb(×10^-9))and left putamen(70.0051±3.5767ppb(×10^-9))in MCI group were significantly higher than that of NC group(-14.4431±3.0961,86.9015±4.6743,114.1169±6.8395,55.6117±4.0072 ppb(×10^-9),P<0.05).There was no difference in other regions between the two groups（P>0.05）.When the cutoff value of left hippocampus was 6.8967 ppb(×10^-9),the AUC was 0.907（95%CI,0.819-0.996）,and the accuracy,sensitivity and specificity was 88.7%、82.1%and 96.0%.When the cutoff value of left dentate nucleus was 116.4287 ppb(×10^-9),the AUC was 0.693（95%CI,0.550-0.835）,and the accuracy,sensitivity and specificity was71.7%、53.6%and 92.0%.When the cutoff value of right substantia nigra was 114.4592ppb(×10^-9),the AUC was 0.743（95%CI,0.608-0.878）,and the accuracy,sensitivity and specificity was 75.5%、82.1%、68%.When the cutoff value of left putamen was 63.1600ppb(×10^-9),the AUC was 0.700（95%CI,0.556-0.844）,and the accuracy,sensitivity and specificity was 69.8%、64.3%、76.0%.3.Correlation analysis showed that the QSM values of left hippocampus,left dentate nucleus,right substantia nigra and left putamen were negatively correlated with Mo CA scores（r=-0.610,P<0.001;r=-0.308,P=0.025;r=-0.391,P=0.004;r=-0.366,P=0.007）.No significant correlation was found between the QSM values of all ROIs and the serum Al concentration（P>0.05）.Conclusion:1.QSM can be used to identify MCI and NC,and assess the degree of cognitive decline of occupational Al workers.The QSM values of left hippocampus,left dentate nucleus,right substantia nigra and left putamen increased,and was negatively correlated with the MOCA score.Among them,left hippocampus showed the best diagnostic efficacy.QSM is expected to become a more reliable imaging marker for the diagnosis of MCI.2.The serum Al concentration of MCI group was higher than that of NC group,and no significant correlation was found between the QSM values of all ROIs and the serum Al concentration.