Objective: To evaluate the value of virtual non-calcium (VNCa) technique of dual-energy CT (DECT) for detecting bone marrow edema (BME) around nontraumatic osteonecrosis of the femoral head (ONFH) using MRI as reference standard. Methods: Nontraumatic ONFH patients were prospectively studied in the Fourth Medical Center of Chinese PLA General Hospital from October 2022 to May 2023, and their MRI and DECT images were analyzed. The diagnostic efficiency of the subjective assessment of BME around ONFH by two radiologists in VNCa color-coded images were calculated using the MRI results as the reference standard. The BME ranges were compared between VNCa images and MRI. Traditional CT values and VNCa CT values were compared between normal bone marrow and BME. The receiver operator characteristic (ROC) curve was established based on the statistically different CT values, and the area under the curve (AUC) was calculated to find the threshold to distinguish normal bone marrow from BME and evaluate the diagnostic efficacy. Results: Thirty patients with ONFH were included, including 24 males and 6 females, aged (39±12) years. There were 18 bilateral hips and 12 unilateral hips, with a total of 48 hips, 34 hips of which showed BME on MRI. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of subjective detection of BME on VNCa color coded maps by two physicians were 97.1% (33/34) and 97.1% (33/34), 92.9% (13/14) and 71.4% (10/14), 97.1% (33/34) and 89.2% (33/37), 92.9% (13/14) and 90.9% (10/11), 95.8% (46/48) and 89.6% (43/48), respectively, with no statistical difference (all P>0.05).There was no statistical difference between VNCa color-coded images and MRI in the BME range (P=1.160). The traditional CT values measured by the two radiologists were in good agreement with VNCa CT values, with intraclass correlation coefficient (ICC) of 0.948 (95%CI: 0.908-0.971) and 0.982 (95%CI: 0.969-0.990), respectively. The traditional CT value of normal bone marrow was (400.7±82.8) HU, and that of BME was (443.7±65.7) HU, with no statistical difference (P=0.062). The VNCa CT value of normal bone marrow was (-103.1±27.8) HU, and that of BME was (-32.9±25.7) HU, with statistical difference (P<0.001). The AUC of distinguishing normal bone marrow from BME based on VNCa CT value was 0.958 (95%CI: 0.857-0.995). The best cut-off value was -74.5 HU, and when the VNCa CT value was higher than -74.5 HU, the sensitivity, specificity, PPV, NPV and accuracy of diagnosing BME were 97.1%, 92.9%, 97.1%, 92.9% and 95.8 %, respectively. Conclusion: The VNCa technique of DECT has high efficiency in detecting BME around ONFH, and can accurately demonstrate the range of BME.
目的： 以MRI为参考标准，评价双能CT的虚拟去钙（VNCa）技术对非创伤性股骨头坏死（ONFH）周围骨髓水肿（BME）的检出价值。 方法： 前瞻性纳入2022年10月至2023年5月解放军总医院第四医学中心非创伤性ONFH患者，分析其MRI及双能CT图像。以MRI图像的评价结果作为参考标准，计算两名放射科医师在VNCa彩色编码图像上主观判断ONFH周围BME的诊断效能。比较VNCa图像和MRI显示的BME范围的差异，并比较正常骨髓和BME的传统CT值及VNCa CT值的差异。对于差异有统计学意义的CT值勾画受试者工作特征（ROC）曲线，计算曲线下面积（AUC），找出区分正常骨髓和BME的阈值，评价诊断效能。 结果： 共纳入ONFH患者30例，男24例，女6例，年龄（39±12）岁；其中双侧髋关节18例，单侧髋关节12例，共48个髋关节，其中34个髋关节在MRI上显示BME。两名医师在VNCa彩色编码图上主观检出BME的灵敏度、特异度、阳性预测值（PPV）、阴性预测值（NPV）和准确度分别为97.1%（33/34）和97.1%（33/34）、92.9%（13/14）和71.4%（10/14）、97.1%（33/34）和89.2%（33/37）、92.9%（13/14）和90.9%（10/11）、95.8%（46/48）和89.6%（43/48），差异均无统计学意义（均P>0.05）。VNCa彩色编码图像与MRI对BME范围的显示差异无统计学意义（P=1.160）。两名放射科医师测量的传统CT值和VNCa CT值的一致性较好，组内相关系数（ICC）分别为0.948（95%CI：0.908~0.971）、0.982（95%CI：0.969~0.990）。正常骨髓的传统CT值为（400.7±82.8）HU，BME的传统CT值为（443.7±65.7）HU，差异无统计学意义（P=0.062）；正常骨髓的VNCa CT值为（-103.1±27.8）HU，BME的VNCa CT值为（-32.9±25.7）HU，差异有统计学意义（P<0.001）。基于VNCa CT值区分正常骨髓和BME的AUC为0.958（95%CI：0.857~0.995），最佳截断值为-74.5 HU，当VNCa CT值>-74.5 HU时，诊断BME的灵敏度、特异度、PPV、NPV和准确度分别为97.1%、92.9%、97.1%、92.9%和95.8%。 结论： 双能CT的VNCa技术对非创伤性ONFH周围BME的检出效能较高，且能准确显示BME的范围。.