Objective To evaluate the agreement of the bone mineral density (BMD) measurements by using a phantomless dual-energy CT compared with conventional quantitative CT (QCT) in sheep vertebral specimen. Methods Twenty-three fresh sheep vertebrae were scanned by QCT and dual-energy CT on the same CT scanner which generated dual-energy images from rapid kilovoltage switches. Trabecular BMD analyses of QCT images were performed using QCTpro software. HAP densities (namely BMD) of the same regions were measured for comparison based on HAP-water material pairs. Pearson correlation, paired t-test, intraclass correlation coefficient (ICC), and Bland-Altman plot were applied for consistency assessment. Results BMD derived from DECT images was (286.7±103.8) mg/cm3 in average, and it was significantly lower than the result of QCT, which was (321.3±123.6) mg/cm3. The two result displayed a strong linear correlation (r=0.989, P＜0.001). The ICC between the two measurements was 0.974 (P＜0.001). Bland-Altman plot was applied after log-transformation of the primary data. Most of the different values were within the range of the mean difference±1.96 SD, indicating a high agreement among measurements. Conclusion BMD measurements derived from the dual-energy CT in vitro displayed a high correlation and agreement with BMD measured by QCT. The phantomless dual-energy CT has the potential to be applied in BMD measurement and follow-up clinically.%目的 利用羊椎体标本评价快速千伏切换能谱CT物质分离技术测定的骨松质骨密度与QCT测定的骨密度的一致性.方法 新鲜羊椎体骨3副 (共23个椎体), 在快速千伏切换的能谱CT机上进行能谱模式扫描, 利用物质分离技术获得椎体骨松质的羟基磷灰石含量 (骨密度), 并在同一台CT机上对每副羊骨进行标准QCT扫描, 用QCT骨密度分析软件获得对应感兴趣区内的椎体骨密度.采用Pearson相关性分析、配对样本t检验、组内相关系数及Bland-Altman法进行两种方法测量结果的相关性及一致性分析.结果 能谱CT物质分离技术测得的羊椎体骨密度值为 (286.7±103.8) mg/cm3, 显著低于QCT测量的骨密度值 (321.3±123.6) mg/cm3, 但二者高度线性相关 (r=0.989, P＜0.001).两种方法测量的骨密度值组内相关系数为0.974 (P＜0.001).对原始数据进行对数转换后应用Bland-Altman分析, 差值大部分位于差值平均值±1.96标准差范围内, 提示两种测量一致性好.结论 能谱CT物质分离技术测定的羊椎体骨密度与QCT测定的骨密度的一致性及相关性好, 有望用于临床患者骨密度的评价及随访.
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