Jia Yongjun MMed, Presenter: Nothing to Disclose

Yu Yong MMed, Abstract Co-Author: Nothing to Disclose

Yang Chuangbo MMed, Abstract Co-Author: Nothing to Disclose

Chen Xiaoxia MMed, Abstract Co-Author: Nothing to Disclose

Zhang Xirong MMed, Abstract Co-Author: Nothing to Disclose

To assess the value of spectral CT in reducing artifacts caused by metallic implants of lumbar pedicle.

20 patients with metallic implants of lumbar pedicle were scanned using dual energy spectral CT protocol. 11 sets of monochromatic images from 40-140keV with the energy interval of 10keV and a set of polychromatic 140kVp image were generated. Two regions of interest (ROI) based on the most or the less pronounced artifact in the inferior vena cava were chosen and marked as ROIa and ROIb to measure CT numbers and calculate their difference CTa-CTb. The length of metallic artifacts along the pedicle screw was measured, and the subjective image quality assessed for the 12 image sets. The CT numbers of different ROIs for the 12 sets were compared with paired-samples t Test, and the CTa-CTb value, artifact length and image quality score (5 being the best) among the 12 sets were compared using LSD-t test.

The CT numbers between ROIa and ROIb of the 120 keV monochromatic images（figure 1）had no difference (42.50±3.64HU and 42.34±3.49HU), while those of other image（figure 2）sets were statistically different. Image at 120keV had the smallest CTa-CTb value (0.16±1.65HU) and was significantly different from those of other 11 groups (all P＜0.05), indicating less CT number alternation by implants for the surrounding tissues at 120keV. The artifact length of pedicle screw was the smallest at 2.84±1.73cm in the optimal monochromatic (120keV) image set and was significantly better than the 5.12±2.51cm in the polychromatic 140kVp images (p<0.05). Image quality of spectral images was superior to the polychromatic images (4.5±0.5 at 120keV vs. 2.8±0.4 with 140kVp, P＜0.001).

Dual energy spectral CT imaging significantly reduced the artifacts caused by metallic implants of lumbar pedicle. The optimal monochromatic image was determined at 120keV.

Spectral CT provides monochromatic images at high energy to reduce metal artifacts and is useful in assessing patients with metallic implants of lumbar pedicle.

Yongjun, J, Yong, Y, Chuangbo, Y, Xiaoxia, C, Xirong, Z, Reducing Artifacts from Metallic Implants Spectral CT Imaging after Pedicle Screw Internal Fixation.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012460.html