Effect Of Abdominal Adipose On Spine Phantom Bone Mineral Density Measured By Dual-Energy Spectrum CT And Quantitative CT

Objective:Abdominal adipose content can have effects on the accuracy of vertebral bone mineral density(BMD)measured by dual-energy spectrum computed tomography(DECT)and quantitative computed tomography(QCT),which needs to be further investigated.Therefore,the purpose of this study was to investigate the effect of abdominal adiposity,as measured by abdominal total adipose tissue(TAT),on the accuracy of DECT and QCT measurements of bone BMD in a spine phantom model.Methods:Fresh porcine fat was wrapped around the European Spine Phantom(ESP)and divided into four groups according to the TAT cross-sectional areas,S=0,100,200,and 350 cm~2,to simulate different TAT contents.Each group of phantom was scanned 10 times using DECT and QCT respectively.The hydroxyapatite(HAP)(water)values of the L1,L2,and L3 vertebrae of the phantom were measured using the DECT material decomposition and quantitative analysis function,and the BMD values of the L1,L2,and L3 vertebrae of the phantom were measured by QCT.A one-sample t-test was used to analyze the differences between the measurements and the true values of the ESP.One-way analysis of variance(ANOVA)test followed by the post hoc Tukey honest significant difference(HSD)test was applied to compare the differences between measurements under different TAT conditions,and the root-mean-square errors(RMSEs)of the BMD measurements were calculated and compared.Moreover,Pearson’s correlation analysis was performed for the RMSE and TAT.Linear regression analysis was conducted on the BMD measurements,the phantom true values,and the TAT of DECT and QCT to obtain the correction equations of BMD for both scanning methods,which were substituted into an additional independent data set(S=320 cm~2)for validation,and to compare the RMSE before and after correction.and the RMSE before and after correction was further compared.Results:There was a significant difference between the BMD measurements and the true values of the phantom for both DECT and QCT under different TAT conditions.In the comparison between measurements under different TAT conditions,both DECT and QCT showed no statistically significant differences between measurements in the lower TAT groups(TAT=0,100,200 cm~2)(p>0.05),while at higher TAT content,the measurements of both scanning methods were more affected,and the measurements of the TAT=350 cm~2 group were significantly different from the remaining groups(P<0.05).The RMSE of the DECT measurements were smaller than those of QCT,and there was a positive correlation between the RMSE of the measurements and TAT for both scanning methods(DECT:L1 r=0.953,p<0.05;L2 r=0.957,p<0.05;L3 r=0.961,p<0.05;QCT:L1 r=0.999,p<0.01;L2r=0.996,p<0.01;L3 r=0.975,p<0.05),with the RMSE of the L1 vertebrae the largest under the same TAT content.After linear regression analysis,the equation for the correction of the BMD measurements of the DECT and QCT was derived,and the RMSE of BMD was significantly reduced after correction.Conclusions:The measurements of ESP BMD for both DECT and QCT changed with TAT content.Along with the increase of TAT,the RMSE of measurements increased and the accuracy decreased;moreover,the lower the value of BMD,the more significant the RMSE;the RMSE of DECT was smaller than that of QCT.The linear regression analysis allowed the corrected BMD measurements to be very close to true values.