无体模法定量CT测量腰椎骨密度的可信度及可重复性研究

Reproducibility of measurement of lumbar vertabal bone mineral density using quantitative CT without external reference phantom

目的评价无体模法定量CT(quantitative computed tomography,QCT)测量腰椎骨密度(bone mineral density,BMD;QCT-BMD)的同一位测量者内和3位测量者间BMD测量值的一致性和可重复性。方法将31例患者的腰椎螺旋CT扫描数据传输至工作站进行BMD测量。由3位经过培训的脊柱外科医生(分别为测量者A、B、C)独立进行腰椎QCT-BMD测量,每位测量者对患者均测量2次。同一位测量者的2次测量和3位测量者间BMD测量值的差异用重复测量的方差分析比较,一致性分析用组内相关系数(intraclass correlation coefficient,ICC)描述。3位测量者间BMD测量值的可靠性分析用Cronbach’sα系数描述。结果测量者A的2次腰椎BMD测量值分别为(67.14±26.71)mg/cc、(66.37±26.69)mg/cc,差值率为4.22%±2.55%(P=0.12,ICC=0.995);测量者B的2次腰椎BMD测量值分别为(68.89±29.37)mg/cc、(68.54±28.98)mg/cc,差值率为5.08%±3.83%(P=0.56,ICC=0.994);测量者C的2次腰椎BMD测量值分别为(69.31±26.72)mg/cc、(69.83±27.90)mg/cc,差值率为4.16%±3.03%(P=0.31,ICC=0.995)。3位测量者所测量的腰椎BMD平均值分别为(66.76±26.66)mg/cc、(68.71±29.13)mg/cc、(69.57±27.28)mg/cc(P=0.15,ICC=0.957,Cronbach’sα系数=0.985)。结论无体模法QCT测量腰椎BMD具有较高的一致性和可重复性。

Objective To evaluate the intra- and inter-observer consistency and reproducibility of bone mineral density （BMD） in lumbar vertebrae measured by quantitative CT without external reference phantom. Methods The CT data of 31 cases were transferred to a work station to measure lumbar BMDs. The BMDs were measured by three trained spine surgeons. Each observer performed the measurements of all subjects twice. Intra-observer and inter-observer variability was calculated using analysis of variance of the repeatedly measured results. The consistency was analyzed with the intra-class correlation coefficient （ICC）. Reliability analysis in inter-observer was performed with Cronbach＇s α coefficient. Results Data measured by Observer A were （67.14 ± 26.71） mg/cc and （66.37 ± 26.69） mg/cc[difference： （4.22 ± 2.55） %, P=0.12, ICC=0.995], Observer B （68.89 ± 29.37） mg/cc and （68.54 ± 28.98） mg/cc[difference：（5.08 ± 3.83）%, P=0.56, ICC=0.994], Observer C （69.31 ± 26.72） mg/cc and （69.83 ± 27.90） mg/cc[difference：（4.16 ± 3.03）%, P=0.31, ICC=0.995], respectively. The mean lumbar BMDs by the three observers were （66.76 ± 26.66）, （68.71 ± 29.13） and （69.57 ± 27.28） mg/cc, respectively （P=0.15, ICC=0.957, Cronbach＇s α coefficient=0.985）. Conclusion High reproducibility and consistency in the measurement of lumbar BMD can be achieved with quantitative CT without external reference phantom.