ABSTRACT
Objective To investigate the clinical feasibility of using gemstone spectral image (GSI)technique to reduce the individual dose of contrast agent in performing lower extremity angiography.Methods Among the consecutive 75 patients receiving lower extremity CTA examination,60 patients were enrolled in this study.According to the scanning method and contrast dosage,the 60 patients were prospectively and randomly divided into the conventional CT routine-dose group (n=20),GSI routine-dose group (n=20) and GSI low-dose group (n=20).In the conventional CT routine-dose group and GSI routine-dose group,the dosage of contrast medium was 2 ml/kg and the injection rate was 3.5 ml/s.Scanning with 120 kVp and reconstruction with filter back projection (FBP) technology were used in the conventional CT routine-dose group,while scanning with spectrum mode and reconstruction with 50％ adaptive statistical iterative reconstruction (ASiR) technology were used in the GSI routine-dose group.In the GSI low-dose group,the dosage of contrast medium and the injection rate were 1.6 ml/kg and 2.8 ml/s respectively,and scanning with spectrum mode and reconstruction with 50％ ASiR technology were adopted.The target vessel CT values of three sets of images were determined,the contrast-to-noise ratio (CNR),the background noise (BN),the dose length product (DLP),the effective dose (ED),the iodine intake dose and the injection rate were calculated and compared between each other among the three groups.Single factor variance analysis and Bonferroni correction method were used to statistically analyze the results.By using Kruskal-Wallis test,the subjective scores of three sets of images were compared between each other among the three groups.Results According to exclusion criteria,60 patients were finally enrolled in this study.The images of GSI routine-dose group had the best CT value,CNR and BN (P＜0.01),but there was no statistically significant difference in BN between GSI routine-dose group and GSI low-dose group (P＞0.05).Both the CT value and CNR,except anterior tibial artery (P=0.162 and P=0.376 respectivcly),in the GSI low-dose group were higher than those in the conventional CT routine-dose group (P＜0.05).The ED values of both GSI groups were lower than that of the conventional CT routine-dose group (P＜0.01),although no statistically significant difference in ED value existed between the two GSI groups (P＞0.05).The iodine intake dose and injection rate of the GSI lowdose group were strikingly lower than those of the conventional CT routine-dose group and the GSI low-dose group (both P＜0.01).The subjective scores of three sets of images evaluated by two physicians were 82,95,90 points and 80,96,89 points respectively,the differences were statistically significant (H=14.954,P＜0.01;H=17.726,P＜0.01).GSI routine-dose group had the best image quality,and the image quality of GSI low-dose group was superior to that of conventional CT routine-dose group (P＜0.05).Conclusion Compared with conventional spiral CT scanning,gemstone optimal monochromatic imaging technique can obtain more optimal CNR and image quality,meanwhile,the radiation dose can be remarkably reduced while the imaging quality of lower extremity angiography can meet the requirements of making clinical diagnosis,moreover,individual intake of iodine can be reduced.