摘要目的 评估双能量CT虚拟去钙(VNCa)图像诊断膝关节外伤性骨髓损伤的价值.方法 连续选取80例因膝关节急性外伤而怀疑有骨折的患者行双能量CT检查,根据膝关节骨挫伤诊断标准及排除标准,最终纳入32例患者.32例患者均行MRI检查.运用双能量CT软件去除钙质生成VNCa图像,将股骨下端及胫骨上端各分成6个区域,2名医师对VNCa图像和MRI图像上每个区域骨髓损伤进行分级(4级,非常明显的损伤;3级,较明显的损伤;2级,VNCa图像有轻微或可疑损伤,MRI图像上有轻微损伤;1级,表示无损伤).对VNCa和MRI图像显示的骨髓损伤行对照分析,以MRI图像为参考标准,将3、4级骨髓损伤视为骨挫伤,评估VNCa图像诊断膝关节骨挫伤的预测值.测量所有分区的骨髓CT值,作基于骨髓CT值的VNCa图像诊断骨挫伤的ROC曲线分析,并比较VNCa图像上真阳性和真阴性骨挫伤区骨髓的CT值.2名医师对骨髓损伤分级的一致性及VNCa与MRI图像显示骨髓损伤的一致性分析采用Kappa检验,骨髓CT值比较采用Mann-Whitney U检验.结果 VNCa及MRI图像上骨髓损伤分级在2名医师间的一致性均非常好(VNCa和MRI的Kappa值分别为0.850和0.869,P值均＜0.05),VNCa和MRI图像显示骨髓损伤的一致性好(股骨下端、胫骨上端Kappa值分别为0.659、0.799,P值均＜0.05).以MRI图像为参考标准,93.7％(119/127)骨髓损伤在VNCa图像上显示.将3、4级骨髓损伤视为骨挫伤时,VNCa图像诊断股骨下端骨挫伤的敏感度、特异度、阳性预测值和阴性预测值分别为73.5％(36/49)、98.6％(141/143)、94.7％(36/38)和91.6％(141/154),胫骨上端相应的各值分别为91.0％(61/67)、100.0％(125/125)、100.0％(61/61)和95.4％(125/131).基于骨髓CT值,VNCa图像诊断股骨下端和胫骨上端骨挫伤的ROC曲线下方的面积分别为0.875和0.939.VNCa图像上股骨下端骨挫伤真阳性区和真阴性区的骨髓CT值的中位数和范围分别为-43.0(-81.2～ 47.4)HU和-91.3(-162.1-50.4)HU,胫骨上端相应CT值分别为-54.6(-96.6～55.4)HU和-103.1(-170.2-70.5)HU,差异均有统计学意义(股骨下端及胫骨上端Z值分别为-8.561和-10.365,P值均＜0.01).结论 双能量VNCa图像可显示膝关节外伤性骨髓损伤CT值变化,可用于诊断膝关节骨挫伤.

abstractsObjective To evaluate dual-energy CT virtual noncalicium (VNCa) images in the diagnosis of traumatic injury of bone marrow in the knee.Methods Eighty consecutive patients suspected for fractures due to acute knee trauma were included in this study and underwent dual-energy CT examinations.According to the diagnostic criteria of bone bruise and exclusion criteria,32 patients were included in the study eventually.These 32 patients underwent MR examinations.The VNCa images were generated by subtracting calcium using the dual-energy CT software.Inferior femur and superior tibia on images were segmented into 6 regions each.The bone marrow lesions on VNCa and MR images were rated with a 4-point scale for each region by two radiologists (4=significant bone marrow lesion; 3=not significant but yet clearly visible bone marrow lesion; 2=mild or suspicious bone marrow lesion on VNCa images or mild bone marrow lesion on MR images; 1=normal bone marrow).Bone marrow lesions on VNCa images were compared to those on MR images,which served as the standard of reference.The bone marrow lesions with scores of 3 and 4 were regarded as bone bruise.The predictive values of VNCa images in the diagnosis of bone bruise were evaluated.CT values of bone marrow were measured for each region and subjected to receiver operating characteristic (ROC) curve analysis for diagnosis of bone bruise.CT values of bone marrow with true positive and true negative bone bruise were also compared.Kappa statistics was used to evaluate the agreement of rating of bone marrow lesions between the two radiologists and the agreement of bone marrow lesions between VNCa and MR images.Mann-Whitney U test was used for comparison of CT values of bone marrow.Result Rating of bone marrow lesions between the two radiologists showed very good consistency (Kappa values were 0.850 and 0.869 for VNCa and MR images,respectively,all P values＜0.05),and bone marrow lesions shown on VNCa and MR images had good consistency (Kappa values were 0.659 and 0.799 for the inferior femur and superior tibia,respectively,all P values＜0.05).When MR images served as the standard of reference,93.7％ (119/127) bone marrow lesions were detected on VNCa images.The sensitivity,specificity,positive predictive value and negative predictive value for diagnosis of bone bruise using VNCa images were 73.5％ (36/49),98.6％ (141/143),94.7％ (36/38) and 91.6％ (141/154) for the inferior femur and 91.0％ (61/67),100.0％ (125/125),100.0％ (61/61) and 95.4％ (125/131) for the superior tibia,respectively.Based on the CT values of bone marrow,the areas under the ROC curves for the diagnosis of bone bruise using VNCa images were 0.875 in the inferior femur and 0.939 in the superior tibia.The CT values of bone marrow in true positive and true negative bone bruise regions on VNCa images were-43.0 (-81.2-47.4) HU and-91.3 (-162.1--50.4) H U in the inferior femur and-54.6(-96.6-55.4)HU and-103.1 (-170.2--70.5)HU in the superior tibia,respectively,and there were statistical differences in the CT values of bone marrow between the true positive and true negative bone bruise regions (for inferior femur Z=-8.561; for superior tibia Z=-10.365,both P values＜0.01).Conclusion The VNCa images can reveal the changes of CT values in the traumatic bone marrow lesions,which can be used to diagnose the bone bruise in the knee.