Flash Dual-source CT With Low-concentration Contrast Material And Low Tube Voltage For Preoperative Evaluation In Living Renal Donors

Objective To investigate the feasibility of using low concentrations of isotonic contrast agent (270mgI/ml) combined with low voltage(80kVp) in preoperative Flash dual-source CT examination of living-donor kidney transplantation and evaluate the influence on image quality of reduced radiation dose and reduced contrast agent.Materials and methods Collect 45 cases (BMI18.5～28kg/m2) who underwent living-donor kidney transplantation during march 2013 to february 2015,including 9 male cases and 36 female cases, age range from 46 to 68, these cases were randomly divided into A,B,C three groups(each 15 cases),groupA; (4 male cases,11 female cases,age 54.7±5.6),iodixanols 320mgI/ml, the tube voltage 120kV, automatic mA, iterative reconstruction technique.group B;(1 male case,14 female cases,age 55.8±6.5),iodixanols 320mgI/ml, the tube voltage 80kV, automatic mA, iterative reconstruction technique.group C;(4 male cases,11 female cases,age 56.0±5.7),iodixanols 270mgI/ml, the tube voltage 80kV, automatic mA, iterative reconstruction technique.Three groups of cases underwent dual-source CT (Siemens SOMATOM Definition FLASH) respectively including unenhanced scan and enhanced multi-phase scan(arterial、venous and excretory phase),inject isotonic contrast agent by antecubital vein,the dose is 1.0ml/kg, the contrast agent injection rate is 4ml/s.Images reconstructed was done on arterial phase,record the CT value(average value±SD) of abdominal aorta in renal artery level、proximal part of right renal artery、proximal part of left renal artery、paraspinal muscles and the rectus abdominis.Calculate CNR and SNR,all above can be as objective analysis indicators of image quality,CNR=(SI vessel-SI muscle)/noise,SNR=SI vessel/noise,vascular enhancement CT value(SI vessel) is an average CT value of the region of interest of abdominal aorta in renal artery level,proximal part of right renal artery and proximal part of left renal artery,SI muscle is the average CT value of the central position of the rectus abdominis and the deep paraspinal muscles,noise is defined as the average standard deviation of the above CT value measurements.Four point criteria was used as subjective evaluation of image quality.1 point represents the image quality can not meet the diagnosis.2-4 point represents the image quality can meet the diagnosis. Statistic three groups of cases who underwent nephrectomy surgery and evaluate the compliance rate between the intraoperative findings and the CTA results.Record CT volume dose index,Dose-length product,Effective dose(ED).SPSS 13.0 statistical software is used for data analysis, chi-square test and ANOVA analysis are used for technical data.ANOVA anylysis is used for SI vessels, noise, SNR,CNR and radiation dose, t test is used for pairwise comparisons, P<0.05 means the difference was statistically significant.Results All images can meet the diagnostic requirements (both>2 point), and no significant adverse reactions. (1)Three groups cases had no statistical significance in age,sex and BMI (2)SI vessel in selected segments were statistically significant among the three groups,group A (242.43±41.87) is lower than group B、C (416.05±47.70、 375.71±39.02).(3)The CT value of rectus abdominis muscle in arterial phase had no statistical significance among the three groups;the paraspinal muscles had statistical significance and group A (49.62±5.26)>group B (47.24±3.27)>group C (46.23±3.27).(4)The noise of the vessels and muscles in each group were statistically significant, group C were greater than group A. (5)SNR and CNR showed no statistical difference among the three groups (P> 0.05).(6)four phase CT scans (unenhanced, arterial, venous and excretory phase) of three groups the volume CT dose index (CTDIvoI) were 20.85mGy,10.59 mGy,9.46 mGy. group B declined by 49% compared with group A, group C decreased by 55% compared with group A.(7)Renal vessels of the intraoperative findings are consistent with the CTA results before surgery.Conclusion Low tube voltage (80kVp) combined with low concentrations of the contrast agent isotonic (270mgI/ml) that used in the renal artery CTA was feasible.Under the premise of the image quality assurance,the radiation dose decreased by 50%, iodine intake was significantly lower.