Automatic diagnostic system for identifying individuals with osteoporosis on panoramic radiographs

最近的研究表明，牙科全景片上的下颌骨下皮质形态可能是识别骨质疏松个体的有用指标。然而，该指标的诊断性能在很大程度上取决于观察者的经验，因为全景X线片上皮质形状的分类是主观确定的。为了客观地诊断皮质形态，我们开发了计算机辅助诊断(CAD)系统，该系统能够自动确定全景X线片上皮质形态的分类。采用双能X线骨密度仪对200例绝经后妇女进行腰椎和股骨颈骨密度(BMD)测定。利用数学形态学方法构建了计算机辅助设计系统。用100张全景X线片开发CAD系统，以识别低骨密度女性，并用100张全景X线片评价CAD系统的有效性。低骨密度定义为骨密度T评分为-1.0或更低。在二分二乘二表中计算CAD识别低骨量骨密度的敏感性、特异性、预测值和准确性。还计算了风险指数为正的可能性比。以腰椎骨密度为标准，其敏感性和特异性分别为73.8%(95%CI，63.1~84.5%)和68.6%(95%CI，53.2~84.0%)。以股骨颈骨密度为标准，分别为66.2%(95%CI，54.9~77.4%)和56.7%(95%CI，38.9~74.4%)。腰椎和股骨颈的似然比分别为2.35(95%CI，1.41~3.91)和1.53(95%CI，0.98~2.38)。这些结果表明，应用于全景X线片的CAD系统可能有助于识别低骨量骨密度

Recent studies suggest mandibular inferior cortical shape on dental panoramic radiographs may be the useful indicator for the identification of individuals with osteoporosis. However, the diagnostic performances of this index largely depend on the experience of observers because the classification of cortical shape on panoramic radiographs is determined subjectively. In order to diagnose the cortical shape objectively, we developed computer-aided diagnosis (CAD) system that automatically can determine the classification of cortical shape on panoramic radiographs. Two hundred panoramic radiographs of postmenopausal women who had bone mineral density (BMD) assessment at the lumbar spine and the femoral neck by dual energy x-ray absorptiometry were used for this purpose. CAD system was constructed by mathematical morphology. One hundred panoramic radiographs were used for the development of CAD system in order to identify women with low BMD, and another 100 panoramic radiographs were used to estimate the validation of CAD system. Low skeletal BMD was defined as a BMD T score of -1.0 or less. The sensitivity, specificity, predictive values, and accuracy of CAD for the identification of low skeletal BMD were calculated in dichotomous 2 by 2 tables. The likelihood ratio for a positive risk index was also calculated. The sensitivity and specificity were 73.8% (95% CI, 63.1 to 84.5%) and 68.6% (95% CI, 53.2 to 84.0%), respectively, when BMD of the lumbar spine was used as a standard. Those were 66.2% (95% CI, 54.9 to 77.4%) and 56.7% (95% CI, 38.9 to 74.4%), respectively, when BMD of the femoral neck was used as a standard. The likelihood ratio was 2.35 (95% CI, 1.41 to 3.91) at the lumbar spine and 1.53 (95% CI, 0.98 to 2.38) at the femoral neck, respectively. These results suggest CAD system applied for panoramic radiographs may be useful for the identification of low skeletal BMD