Department of Radiology, University Hospitals Cleveland Medical Center, Case Western Reserve University, Cleveland, OH, USA.
Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
Skeletal Radiol. 2019 Dec;48(12):1981-1990. doi: 10.1007/s00256-019-03248-3. Epub 2019 Jun 1.
Metal artifacts limit the diagnostic utility of computerized tomography (CT) for implant-related complications. Dual-layer spectral detector CT imaging has been suggested for artifact reduction. Our objective was to evaluate the utility of spectral CT in artifact reduction in patients with small and large metal implants.
In this prospective study, patients with metallic orthopedic implants underwent CT imaging using a prototype spectral detector CT scanner. Conventional images were generated with iterative reconstruction at 120 kVp, and virtual monochromatic images were generated at 20-keV intervals between 40 to 200 keV. Conventional and monochromatic images were compared quantitatively using signal-to-noise ratio (SNR) and artifact improvement. Qualitative analysis was performed independently by two musculoskeletal radiologists and included six image quality indicators.
A total of 12 patients were scanned. In monochromatic images, as the energy level increased, the artifact size decreased progressively (p < 0.01). When conventional and monochromatic images were compared, maximum reduction was seen at 200 keV. Using qualitative assessments, 160 and 180 keV levels had the best overall diagnostic image quality. With increased energy level, there was improvement in qualitative ratings of bone-metal interface conspicuity (p = 0.002), degree of streak artifact (p = 0.010) and trabecular bone definition at 1 cm from implant (p = 0.023), and a trend towards significance for bone definition at 5 cm, soft tissue detail and overall diagnostic quality. Subgroup analysis revealed superior artifact reduction in small implants compared to large hardware.
Our results support the utility of dual-layer spectral CT in metal artifact reduction. Virtual monochromatic images were diagnostically superior, especially for smaller implants. Virtual monoenergetic images at 160-180 keV are ideal for reducing artifacts.
金属伪影限制了计算机断层扫描（CT）在植入物相关并发症诊断中的应用。双层能谱探测器 CT 成像技术已被用于减少伪影。我们的目的是评估光谱 CT 在减少小和大金属植入物患者伪影方面的作用。
在这项前瞻性研究中，有金属骨科植入物的患者使用原型能谱探测器 CT 扫描仪进行 CT 成像。使用 120 kVp 的迭代重建生成常规图像，在 40 至 200 keV 之间以 20 keV 的间隔生成虚拟单能量图像。使用信噪比（SNR）和伪影改善程度对常规图像和单能量图像进行定量比较。两位肌肉骨骼放射科医生独立进行定性分析，包括六个图像质量指标。
共扫描了 12 名患者。在单能量图像中，随着能量水平的增加，伪影大小逐渐减小（p < 0.01）。当比较常规图像和单能量图像时，在 200 keV 时最大程度地减少了伪影。使用定性评估，160 和 180 keV 水平具有最佳的整体诊断图像质量。随着能量水平的增加，骨-金属界面清晰度（p = 0.002）、条纹伪影程度（p = 0.010）和植入物 1 cm 处的小梁骨清晰度的定性评分有所改善，而在植入物 5 cm 处、软组织细节和整体诊断质量的改善具有统计学意义。亚组分析显示，在小植入物中，双层能谱 CT 减少伪影的效果优于大植入物。
我们的结果支持双层能谱 CT 在减少金属伪影方面的作用。虚拟单能量图像具有更好的诊断效果，尤其是对于较小的植入物。160-180 keV 的虚拟单能量图像是减少伪影的理想选择。
