Effectiveness of iterative metal artifact reduction for reduction of metal artifact in chest CT scanning / 中国医学影像技术

ABSTRACT

Objective To assess the effectiveness of iterative metal artifact reduction (IMAR) on metal artifacts reduction in thorax scan.Methods Thoracic phantom with two pedicle screws implanted in both sides of the T5 vertebrae was used,with the scan parameters of 130 kV and CARE Dose 4D,the phantom was scanned with and without the screws respectively.Images without screws were reconstructed with FBP.Images with screws were reconstructed with FBP and IMAR respectively.Three ROIs were selected on tissues including aorta,pulmonary and paravertebral soft tissue on image slice adjacent to the screws.The CT value and standard deviations (noise) of ROIs were measured,and the deviation of CT value (△HU) was calculated as the difference between CT values in images with and without screws.Twenty-six cases who received chest CT examination and with pedicle screw implant in scanning range were collected.The scanning parameters and image reconstruction methods were the same as phantom scan.The CT value (HU) of metal artifacts adjacent to vertebrae and dorsal soft tissue was measured,and the image quality of reconstructed image by two skilled radiologists independently was evaluated.Results In the phantom after implanted screws,the noise were significantly reduced by IMAR compared to FBP in all the three ROIs of aorta,pulmonary and paravertebral soft tissue (P＜0.05),and the △HU was significantly smaller in IMAR compared to that with FBP (P＜0.01).In 26 patients,there were significant differences in CT value of vertebral bone tissue and dorsal soft tissue between FBP and IMAR (P＜0.05),and the subjective evaluation scores of the two image reconstruction methods showed a statistically significant difference (P＜0.05).Conclusion IMAR can significantly reduce streak artifacts of metal implant and adjuste the CT values of artifact affected tissues to make it more close to the true value without metal implant.