双能量CT虚拟去钙成像在鉴别急慢性椎体压缩性骨折中的研究

Dual energy CT virtual noncalcification imaging in differentiating acute and chronic vertebral compression fractures

目的探讨双能量CT虚拟去钙成像用于鉴别急慢性椎体压缩骨折的临床价值。方法双源CT对34例胸腰椎压缩改变患者进行双能去钙成像,以MRI图像作为参照标准。由两名医师使用2分法分别对压缩椎体进行独立评价,使用Kappa检验评价二者间的一致性。由另一名医师在去钙图像上测量椎体骨髓密度(CT值),同时选取参考椎体,测量并计算两者CT值的差值。使用ROC分析检验主观评分、骨髓密度值及密度差值,使用t检验比较急性骨折和陈旧骨折骨髓的密度值及CT差值。结果在58个压缩椎体中,MRI图像发现32个有骨髓水肿,两名医师在去钙图像上分别诊断25个和30个椎体有骨髓水肿,骨髓水肿主观评分的一致性较高(Kappa=0. 829),主观评分的曲线下面积(AUC)、敏感性、特异性、阳性预测值、阴性预测值准确性较为可靠。t检验示急性骨折水肿骨髓的密度值及CT差值较慢性骨折骨髓高。骨髓密度CT值的ROC分析显示AUC为0. 901,利用约登指数计算诊断阈值为1. 6HU;对骨髓密度CT差值的ROC分析显示AUC为0. 910,诊断阈值为29. 3HU;两者联合的ROC分析显示AUC为0. 924。结论 CT双能去钙图像可用于鉴别急慢性椎体骨折,其客观定量分析的诊断的效能高于主观定性分析,CT值联合CT差值的诊断效能> CT差值>CT值。

Objective To evaluate the clinical value of dual energy CT virtual noncalcium imaging in the diagnosis of acute and chronic vertebral compression fractures. Methods Thirty-four patients with thoracolumbar compression underwent dual-energy CT（DECT） and MRI scan. Noncalcium images were obtained from DECT images. MRI images were used as reference criteria. Two independent doctors evaluated bone marrow edema in noncalcium images with a two-point scale. Kappa statistics was used to test inter-observer agreement. The bone marrow density （ CT value） of vertebral body was measured by another doctor on noncalcium image, the reference vertebral body was selected to measure and calculate the difference of CT value. ROC analysis was used to test the subjective score, bone marrow density value and density difference, and t -test was used to compare the density value and CT difference of the bone marrow with acute and old fractures. Results In the 58 compressed vertebral bodies, 32 were found to have bone marrow edema in the MRI image. Two doctors diagnosed 25 and 30 vertebrae with bone marrow edema, and the consistency of the subjective score of bone marrow edema was higher （Kappa = 0. 829）. The area under the curve of the subjective score （AUC） , sensitivity, and specificity the accuracy of heterosexual, positive and negative predictive values were 0. 817 and 0.791, 68.8% and 75% , 88.4% and 76.9% , 88% and 80, 69.7% and 71.4% , 77.6% , and 75.9%. The bone marrow density value and CT difference of acute fracture edema were higher than those of chronic bone marrow, respectively （ 37.6 ± 41.1） HU vs （-21.6±41.4） HU, （56±21.4） HU vs （13.2±41.4） HU,（ P 〈0.01）. The ROC analysis of bone marrow density CT value showed that AUC was 0.901, and the diagnostic threshold was 1.6 HU using the Jordan index. The ROC analysis of the CT difference of bone marrow density showed that AUC was 0. 910, and the diagnostic threshold was 29.3 HU. The ROC analysis of the two combinations showed that AUC was 0.924. Conclusion CT dual energy noncalcium image can be used to identify acute and chronic vertebral fractures. The effectiveness of the objective quantitative analysis is higher than the subjective qualitative analysis. The diagnostic efficiency of the CT value combined with the CT difference value was 〉 CT difference value 〉 CT value.