Evaluation Of The CT Value Of The Lumbar Vertebrae For Prediction Of Bone Mineral Density Using A New Automatic Phantom-less Quantitative Computed Tomography System

Background:The purpose of this study is to investigate the correlation between the volume bone mineral density(v BMD)measured by quantitative computed tomography(QCT)and the corresponding vertebral attenuation value(CT value)in routine lumbar CT scans,and identified a threshold CT value to predict osteoporosis to guide clinical diagnosis and treatment.Methods:We retrospectively selected 530 patients who received lumbar CT scans at spinal surgery department of China-Japan Union Hospital of Jilin University from July 2022 to September 2022.All patients were assessed using a new automatic phantom-less QCT(PL-QCT)system to reconstruct three-dimensional lumbar CT scans;the regions of interest(ROI)on the L1–L4 vertebrae were selected,and CT value and v BMD were measured.SPSS and Graph Pad Prism software were used to statistically analyze the characteristics between age,sex and v BMD,investigate the correlation between the CT value and v BMD,analyze the receiver operating characteristic(ROC)curve basing on the diagnostic criteria of QCT,calculated the area under the curve(AUC),95%confidence interval(CI),sensitivity,and specificity,and determine the optimal threshold CT value for diagnosing osteoporosis and identifying normal bone.Results:In total,168 men(40.7%)and 245 women(59.3%)(aged 20-88[56.9±13.5]years)were finally included.The CT value and v BMD of1652 vertebrae in 413 patients were measured.The results showed that the v BMD decreased with age in both sexes,women’s decline rate was faster,and v BMD was lower than that of men after age 50.Based on the diagnostic criteria of QCT,1652 vertebral bodies were divided into 418(25.3%)in osteoporosis group,543(32.9%)in osteopenia group and 691(41.8%)in normal bone group,and the average CT value were 68.8±21.5HU,117.5±17.5 HU,and 183.7±33.8 HU,respectively.The scatter plot showed a good correlation between CT value and v BMD(R~2=0.9776),and the linear equation was y=1.174x+0.2118(x=v BMD,y=CT value).ROC analysis showed that the optimal threshold CT value for determining normal bone was≥137.5HU,the AUC was 0.984(95%CI,0.986-0.993).The optimal threshold CT value for diagnosing osteoporosis was≤96.5HU,the AUC was 0.990(95%CI,0.980-0.988).Conclusions:The CT value and v BMD of lumbar vertebrae were significantly correlated.The CT value can be used to indirectly assess the lumbar vertebral v BMD for timely diagnosis of osteoporosis and assist in clinical diagnosis and treatment.