Combining Gemstone Spectral Imaging(GSI) And Snap Shot Freeze(SSF) Reconstruction Technique In CT Coronary Angiography:Lower Dose And Lower Injection Rate Of Contrast Agent

Objective:To investigate the feasibility of applying both gemstone spectral imaging(GSI)and snap shot freeze(SSF)reconstruction technique in CT coronary angiography(CTCA)to lower the dose and the injection rate of contrast agent in patients.Methods:CTCA were performed in 60 patients in the radiology department of Panyu Central Hospital of Guangzhou from October 2014 to April 2018.Patients were randomly divided into two groups : Energy spectrum group(group A)with 30 patients and routine group(group B)with 30 patients.The contrast agent was 370 mg/ml Ultravist,The scanning equipment was 64-layer gemstone energy spectrum CT(Discovery CT750 HD)which made by GE.The gem CT energy spectrum scanning mode was performed in group A to reduce the dosage of contrast agent and at the same time reduce the injection speed of contrast agent.The images of all patients in group A was further reconstructed as two subgroups: subgroup 1,reconstructed at 55 ke V;subgroup 2,reconstructed at 70 ke V.Patients in group B was scanned by using conventional mode.The prospective electrocardiographic gating were used in both groups,Adaptive Statistical Iterative Reconstruction(ASi R)of 50% weight combined with 55 Kev 、 70 Kev reconstruction data of group A,secondly reconstruction was conducted by combining with automatic tracking freezing(Snap Shot Freeze,SSF).The data reconstruction of Group B were conducted under 120 KVP hybrid energy scanning mode,combined with the Filter Back Projection(FBP)and SSF.The image quality was evaluated subjectively.In order to compared the coronary artery image quality of two groups,we calculate the CT value CNR 、 SNR and noise on the anterior descending coronary artery 、 left main cyclotron branch and right coronary artery.The Dose Length Product(DLP),volune CT Dose Index and CTDI,which are automatically generated by the scanning CT machine,are recorded respectively.The effective dose(ED)was calculated.The data obtained were statistically analyzed using SPSS19.0 statistical software.Result:1.There was no statistically significant difference between the two groups(P>0.05)in gender,age,height,weight,et al,thus the two groups were comparable.2.There were significant differences in CTDI,DLP and ED between the two groups,and the data of the group A was lower than that of the conventional group,with statistically significant differences(P<0.05).3.In group A which combined with 50% weight ASi R technology,the SNR and CNR of subgroup 1 were higher than that of subgroup 2,and the noise of subgroup 1 was lower than that of subgroup 2.The subjective quality score of subgroup 1 was better and there were statistically significant differences in subjective scores between the two groups.4.The image SNR and CNR obtained from subgroup 1 in group A with 50% weight ASi R were higher than group B,and the noise was lower than the group B.The statistical results of subjective quality score showed at p=0.561,and there was no statistical difference in the subjective scores of the two groups(p > 0.05).Conclusion:1.When the contrast agent has low dose and low flow rate,55 Kev single-energy reconstruction can achieve higher SNR than 70 Kev,which is more conducive to the development of SSF technology and can better correct the vascular fault and artifacts in patients with the bad heart rate.2.By slowing down the injection rate,reducing the dosage of contrast agent And Combining with 55 Kev single-energy reconstruction and technology after energy spectrum scanning can not only reduce the radiation dose of the patients,but also obtain images which are the same quality compare to conventional coronary angiography.