| Objective To investigate the effect of different amounts of abdominal adipose on the accuracy of low-mA quantitative computed tomography(QCT)measurements of bone mineral density(BMD)in a spine phantom model.Methods Fresh porcine fat of different areas was wrapped around the European Spine Phantom(ESP)to simulate different contents of total adipose tissue(TAT)in human abdomen,which was divided into four groups according to TAT area: TAT=0 cm~2,200 cm~2,320 cm~2,and 420 cm~2.The BMD values of the L1,L2,and L3 vertebrae were measured using routine QCT and low-mA QCT with 10 repeated scans for each group of body models.A one-sample t-test was used to analyze the differences between the measurements obtained from routine QCT and the true values of the ESP.A one-sample t-test was used to analyze the differences between the measurements obtained from lowmA QCT and the true values of the ESP.One-way ANOVA Tukey test was used to compare within-group differences in low-mA QCT measurements under different TAT conditions.The paired-sample t-test was used to compare the differences in BMD measurements for each vertebra between routine QCT and low-mA QCT.The root-meansquare errors(RMSEs)of the BMD measurements were calculated and compared;the correlation between RMSE of low-mA QCT and TAT was observed by Pearson correlation analysis.Results TAT=0cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by routine QCT were 41.13±0.78,98.48±0.76,192.98±1.04,respectively.TAT=200 cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by routine QCT were35.66±0.88,95.61±0.80,190.77±1.11,respectively.TAT=320 cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by routine QCT were 33.49±0.91,92.72±1.03,185.19±1.21,respectively.TAT=420 cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by routine QCT were 32.211±1.26,90.96±1.12,182.59±1.33,respectively.TAT = 0,200,320,420 cm~2,significant differences between BMD measurements by routine QCT and the true values of the ESP were shown(P < 0.05).TAT=0cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by low-mA QCT were 40.89±1.01,97.96±0.98,192.79±1.31,respectively.TAT=200 cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by low-mA QCT were 35.59±1.05,95.05±1.08,190.96±1.37,respectively.TAT=320 cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by low-mA QCT were 33.01±1.18,92.35±1.44,184.66±1.39,respectively.TAT=420 cm~2,the BMD values of the L1,L2,and L3 vertebrae measured by low-mA QCT were 31.01±1.48,88.78±2.69,181.84±1.51,respectively.TAT = 0,200,320,420cm~2,significant differences between BMD measurements by low-mA QCT and the true values of the ESP were shown(P < 0.05).when TAT = 0,200,and 320 cm~2,there were no statistically differences between routine QCT and low-mA QCT measurements(P > 0.05),while TAT = 420 cm~2,significant differences were shown(P < 0.05).The correlation between RMSE of lowmA QCT and TAT in L1,L2 and L3 vertebrae was 0.998,0.970 and 0.970,respectively.The highest correlation was found in the L1 vertebrae.The RMSE of low-mA QCT was positively correlated with TAT(P < 0.05): L1 vertebrae(P=0.002),L2 vertebrae(P=0.027),L3 vertebrae(P=0.028).TAT=0cm~2,the RMSE of L1,L2,and L3 vertebrae measured by routine QCT were3.13,2.07,2.16,respectively.TAT=200 cm~2,the RMSE of L1,L2,and L3 vertebrae measured by routine QCT were 3.85,2.47,2.57,respectively.TAT=320 cm~2,the RMSE of L1,L2,and L3 vertebrae measured by routine QCT were 3.94,3.00,3.43,respectively.TAT=420 cm~2,the RMSE of L1,L2,and L3 vertebrae measured by routine QCT were4.16,3.31,3.60,respectively.TAT=0cm~2,the RMSE of L1,L2,and L3 vertebrae measured by low-mA QCT were 2.90,1.85,2.05,respectively.TAT=200 cm~2,the RMSE of L1,L2,and L3 vertebrae measured by low-mA QCT were 3.57,2.34,2.50,respectively.TAT=320 cm~2,the RMSE of L1,L2,and L3 vertebrae measured by low-mA QCT were4.03,3.24,3.37,respectively.TAT=420 cm~2,the RMSE of L1,L2,and L3 vertebrae measured by low-mA QCT were4.27,3.48,3.64,respectively.TAT = 420 cm~2 group,the RMSEs using routine QCT were smaller than those using low-mA QCT;RMSEs of L1 vertebrae were constantly larger than those of L2 and L3 vertebrae under different TAT conditions.Routine QCT scanning: DLP ranged from 190.90 to 477.68 m Gy·cm,with an average of(380.15±105.19)m G y· cm;Low-mA QCT scanning: DLP was32.64～ 43.31 m G y·cm,with a mean of(38.77±3.07)m G y·cm.Conclusion Low-mA QCT is a reliable method to measure lumbar BMD as accurately as routine QCT for the general population and has a great advantage in radiation dose,while for the overweight/obese people,routine QCT is more accurate. |
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