Objective To investigate the ability of MRI-based synthetic CT (sCT), low-dose CT (ldCT) and radiography to detect spinal new bone formation (NBF) in patients with axial spondyloarthritis (axSpA). Methods Radiography of lumbar and cervical spine, ldCT and sCT of the entire spine were performed in 17 patients with axSpA. sCT was reconstructed using the BoneMRI application (V.1.6, MRIGuidance BV, Utrecht, NL), a quantitative three-dimensional MRI-technique based on a dual-echo gradient sequence and a machine learning processing pipeline that can generate CT-like MR images. Images were anonymised and scored by four readers blinded to other imaging/clinical information, applying the Canada-Denmark NBF assessment system. Results Mean scores of NBF lesions for the four readers were 188/209/37 for ldCT/sCT/radiography. Most NBF findings were at anterior vertebral corners with means 163 on ldCT, 166 on sCT and 35 on radiography. With ldCT of the entire spine as reference standard, the sensitivity to detect NBF was 0.67/0.13 for sCT/radiography; both with specificities >0.95. For levels that were assessable on radiography (C2–T1 and T12–S1), the sensitivity was 0.61/0.48 for sCT/radiography, specificities >0.90. For facet joints, the sensitivity was 0.46/0.03 for sCT/radiography, specificities >0.94. The mean inter-reader agreements (kappa) for all locations were 0.68/0.58/0.56 for ldCT/sCT/radiography, best for anterior corners. Conclusion With ldCT as reference standard, MRI-based sCT of the spine showed very high specificity and a sensitivity much higher than radiography, despite limited reader training. sCT could become highly valuable for detecting/monitoring structural spine damage in axSpA, not the least in clinical trials. Data are available on reasonable request.

中文翻译：

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基于 MRI 的合成 CT：评估中轴型脊柱关节炎患者脊柱结构损伤的新方法 – 与低剂量 CT 和 X 线摄影的比较

目的 探讨基于 MRI 的合成 CT（sCT）、低剂量 CT（ldCT）和 X 线检查对中轴型脊柱关节炎（axSpA）患者脊柱新骨形成（NBF）的检测能力。方法对17例axSpA患者进行腰椎、颈椎X线检查、全脊柱ldCT、sCT检查。 sCT 使用 BoneMRI 应用程序（V.1.6，MRIGuidance BV，Utrecht，NL）重建，这是一种基于双回波梯度序列和机器学习处理流程的定量三维 MRI 技术，可以生成类似 CT 的 MR 图像。图像由四位不了解其他影像/临床信息的读者应用加拿大-丹麦 NBF 评估系统进行匿名和评分。结果 对于 ldCT/sCT/X 线检查，四名读者的 NBF 病变平均评分为 188/209/37。大多数 NBF 发现位于椎体前角，LDCT 平均为 163，sCT 平均为 166，X 线摄影平均为 35。以整个脊柱ldCT为参考标准，sCT/X线检测NBF的灵敏度为0.67/0.13；两者的特异性都 >0.95。对于可通过放射线照相评估的水平（C2–T1 和 T12–S1），sCT/放射线照相的敏感性为 0.61/0.48，特异性 >0.90。对于小关节，sCT/放射线照相的敏感性为 0.46/0.03，特异性 >0.94。对于 ldCT/sCT/X 射线照相，所有位置的平均读者间一致性 (kappa) 为 0.68/0.58/0.56，前角最佳。结论 以 ldCT 作为参考标准，尽管读者培训有限，但基于 MRI 的脊柱 sCT 显示出非常高的特异性和远高于放射线照相的敏感性。 sCT 对于检测/监测 axSpA 的结构性脊柱损伤非常有价值，尤其是在临床试验中。可根据合理要求提供数据。