1.Department of Radiology<2./sup>3.,the First Affiliated Hospital of Nanjing Medical University,<4.sup>5.Nanjing 210029<6.,<7.China<8.<
目的：评估双层探测器光谱CT虚拟单能量图像（virtual monoenergetic image，VMI）联合去金属伪影算法（orthopedic metal artifact reduction algorithm, O-MAR)对于减少骨科金属植入物伪影的价值。方法：共纳入44例检查部位包含骨科金属植入物行光谱CT检查患者。重建传统滤波图像(conventional image，CI)、O-MAR图像、VMI和VMI +O-MAR（100～200 keV，增量为10keV）。在每组图像高密度、低密度伪影区和脂肪组织内勾画感兴趣区，测量CT值、标准差(standard deviation，SD)，计算信噪比（signal to noise ratio，SNR）和伪影指数（artifact index，AI）进行统计分析。由一名放射科医师根据5分法对金属植入物周围骨质和肌肉软组织情况进行两次主观评价。结果：与CI相比，O-MAR、100~200keV VMI和VMI +O-MAR在高密度伪影区内，AI降低（P＜0.05）；而低密度伪影区SNR升高、AI降低（P＜0.05）。相同keV下，两种伪影区内VMI +O-MAR AI均低于VMI（P＜0.05）。100~200keV VMI +O-MAR主观评分均高于VMI图像；在140～160keV时，两种图像评分均大于3分，图像质量满足诊断要求。结论：双层探测器光谱CT VMI+O-MAR可以有效减轻骨科金属植入物伪影，推荐使用140～160keV 的VMI+O-MAR算法重建图像。
Objective: To evaluate the value of a virtual monoenergetic image (VMI) combined with an orthopedic metal artifact reduction algorithm (O-MAR) for double-layer detector spectral CT to reduce orthopedic metal implant artifacts. Methods: A total of 44 patients with examination sites containing orthopedic metal implants undergoing spectral CT were included. CI (conventional image, CI), O-MAR images, VMI and VMI +O-MAR (100～200 keV, increments of 10 keV) were reconstructed. The region of interest was outlined within the and hyperdense and hypodense artifact areas and fat tissue in each group of images, and CT value, standard deviation (SD) were measured, and signal to noise ratio (SNR) and artifact index (AI) were calculated for statistical analysis. Two subjective evaluations of the bone and muscle soft tissue conditions around the metal implants were performed by a radiologist based on a 5-point Likert scale. Results: Compared with CI, O-MAR, 100-200 keV VMI, and VMI +O-MAR, AI decreased in the hyperdense artifact area (P < 0.05); whereas SNR increased in the hypodense artifact area and AI decreased (P < 0.05). In the same keV, VMI +O-MAR AI was lower than VMI in both artifact areas (P < 0.05). 100~200 keV VMI +O-MAR subjective scores were higher than VMI; At 140~160 keV, both image scores were greater than 3 points, and the image quality met the diagnostic requirements. Conclusion: Dual-layer detector spectral CT VMI + O-MAR can effectively reduce orthopedic metal implant artifacts, and the VMI+O-MAR algorithm at 140~160 keV is recommended for image reconstruction.