1. Compare the effect of virtual single energy imaging and virtual single energy combined with MAR technology to remove metal artifacts in the spine. 2. Discuss the most suitable KeV of virtual single energy imaging combined with MAR technology to remove metal artifacts.

The virtual single-energy imaging of energy spectrum CT combined with the metal artifact reduction technology MARS Multi Artifact Reduction System] can effectively reduce the interference of metal artifacts. This is because MAR technology corrects the image through an iterative algorithm, improves the spatial resolution, and restores the details of the adjacent tissue of the metal object. Virtual single-energy imaging technology can effectively reduce hardening artifacts. The two are used in combination to achieve the purpose of reducing metal artifacts. There have been articles about virtual single energy combined with MAR technology to reduce metal artifacts. However, the current researches mostly focus on the comparison of virtual single energy combined with MAR technology and conventional CT examination and virtual single energy imaging. There are few evaluations on the severity of metal artifacts after spinal surgery. According to different surgical methods, metal The difference in the number of implants will result in different artifact reduction effects. Secondly, the current research on the suitable KeV of virtual single energy combined with MAR technology to reduce metal artifacts is less discussed and reported.

Inclusion Criteria:

• Patients undergoing surgery due to lumbar disc herniation or prolapse
• Patients undergoing surgical correction due to vertebral deformities.

Exclusion Criteria:

• The scan image quality caused by the patient's movement and other factors is too poor to meet the diagnostic requirements.
• Patients with only spinous processes and intervertebral spaces undergoing metal fixation after spine surgery
• Patients after spinal cord tumor surgery.

The subjects were selected from patients who planned to undergo routine spinal postoperative CT examinations in the radiology department from December 2018 to February 2019 in Peking University Third Hospital.