The Different Effects On Removing Metal Artifacts By Two Kinds Of Tube Voltage Combination Of DSCT

Background:As the surgical technology for fracture metal fixation is becoming more mature and the material for the metal fixator is becoming more developed, the surgical technology of fracture metal fixation is becoming more widely applicated in clinic. Therefore it is necessary to show the details of the structures at the fracture fixed with metal fixator by medical imaging. Many different methods can be used. X-ray image is the overlapping image which affects the details of structure it shows. As the metal fixator affects homogeneity of the local magnetic field when doing the MRI scan, the metal artifacts can seriously reduce the images quality. The MSCT can form beam hardening artifacts around the metal fixator which can seriously affect the observation of the important structures of the fracture parts. So the quality of images after metal fixation of fractures hadn’t been solved properly for long a time. The Dual Source CT (DSCT) has two sets of the ball-tube detector system. Using different energy levels in two sets, we can collect two different pool of data in one-time scanning, which is called dual-energy scanning sequence. The scanning data can be processed through monoenergetic technique to remove some even all of the metal artifacts and optimize the image quality. The most common used combination of voltage is100KV and140KV, or80KV and140KV. There is no literature about the comparative study on the effects in removing metal artifacts scanned by the two kinds of tube voltage combination so far.Purpose:To discuss the different effects on removing the metal artifacts of the image of the metal fixation of fractures by the two different sets of tube voltage combination(100kv and140kv,80kv and140kv) using monoenergetic technique.Materials and Methods:62patients with metal fixation of fractures were enrolled. The age range of the patients is from19to61years old. The median of age is37years old. All of the patients underwent dual-energy CT scanning twice by the two different sets of tube voltage combination respectively. We used the tube voltage combination of "100kv and140kv"(group1)to scan at the first check and the combination of "80kv and140kv"(group2) at the second check. Each scanning got two different pool of raw data. The raw data was postprocessed by monoenergrtic technique in the dual-energy scanning system software. An experienced radiological technician reconstructed the best quality images with the minimum of metal artifacts with optimised keV (optimised image quality keV, OPT-keV) in subjective vision. Then the technician transferred the best quality images to3D software to reconstruct the final images using multiplanar reconstruction (MPR). Two experienced radiologist evaluated the two groups of images using a5-point score and double-blind trials(l:non-diagnostic to5:excellent). Wilcoxon rank test was applied for the statistical analysis of the image quality produced by the two different sets of tube voltage combination. Kappa test was used to perform the consistency of score made by the two radiologists.Results:All the images were diagnostic.45images of group1were scored above or equal to4points, accounted for72.58%.33images of group2were scored above or equal to4points, accounted for62.90%. There was statistical difference between the two groups (Uc=2.037>1.96,P<0.05).Conclusion:The effect on removing metal artifacts using the tube voltage combination of "100kv and140kv" of dual-energy CT is better than that of using the tube voltage combination of "80kv and140kv".