Iterative Model Reconstructions Application In Ultra-low Radiation Dose CTPV In Patients With Cirrhosis

Objective To explore the application value of iterative model reconstr-uction（IMR）in low radiation dose CTPV in patients with cirrhosis,and t o provide a new method for further reducing the CTPV radiation dose in patients with cirrhosis.Methods 100 patients with liver cirrhosis who underwent upper abdominal venous imaging in the second affiliated hospital of guangxi medical university from January 2018 to March 2019 were selected for the study.100 patients were randomly divided into the control group（group A）and the experimental group（group B）,each group have 50 patients.All patients were performed by Philips256 spiral CT（Brilliance iCT）for upper abdominal enhancement scanning,and the contrast agent was iohexol（350mgI/ml）at a flow rate of 4.0ml/s and a dose of 1.2ml/kg.The scanning range was from the right phalanx to the plane of bilateral anterior superior iliac spine.The arterial scanning started at the beginning of the abdominal aorta using contrast agent tracking detection technology.The monitoring point was the beginning of the abdominal aorta,triggering the scanning threshold of 120HU.The beginning time of portal phase scan was 28S after the end of arterial phase scan.Group A used 100kV,DoseRight Index（DRI）20 and combined iDose4 reconstruction technology,group B used 80kV,DRI17 and combined IMR technology.Independent sample T test was used to compare and analyze the differences in the following data between groups A and B:（1）noise（SD）,signal noise radio（SNR）,contrast noise ratio（CNR）and subjective score of the main portal vein and left and right branches in the two groups;（2）noise（SD）and signal noise radio（SNR）of liver;（3）Volume CT dose index(CTDI_VOL),radiation dose length product（DLP）and Effective radiation dose（ED）of two groups patients.Results 1.The SD,SNR and CNR of the main portal vein,left branches and right branches in group A and group B were statistically different（P=0.000）.The SD,SNR and CNR of the main portal vein in group A were respectively14.53±2.91,13.72±3.14,8.92±3.74;The SD,SNR and CNR of the left branches in group A were respectively 13.63±2.81,14.64±4.13,8.34±3.15;The SD,SNR and CNR of the right branches in group A were respectively 14.58±2.61,13.46±2.76,8.01±2.60;The SD,SNR and CNR of the main portal vein in group B were respectively10.44±2.36,23.85±5.74,19.18±6.32;The SD,SNR and CNR of the left branches in group B were respectively 9.58±1.66,27.88±7.29,19.36±7.18;The SD,SNR and CNR of the right branches in group B were respectively 9.69±1.59,26.76±7.13,17.95±6.35;The final subjective scores of group A and B were respectively 4.17±0.45,4.12±0.62 which has no significant difference.2.The SD and SNR of liver in group A and group B were statistically different（P=0.000）.Group A:The SD and SNR were respectively 12.46±2.05、8.97±2.22;Group B:The SD and SNR were respectively 7.93±2.07、16.27±5.25.3.The CTDI_VOL,DLP and ED of the patient in group A and group B were statistically different（P=0.000）.The CTDI_VOL,DLP and ED in group A were respectively 9.36±1.18mGy,198.83±51.30mGy*cm,3.38±0.87mSv.The CTDI_VOL,DLP and ED in group B were respectively 6.13±1.48mGy,136.85±39.34mGy*cm,2.33±0.67mSv.Conclusion Iterative model reconstruction can significantly improve the liver parenchyma and CTPV image quality of patients with liver cirrhosis at low radiation dose,which can be used in low radiation dose CTPV of patients with liver cirrhosis.