Study On The Application Of Low-dose CT Technique In Right Adrenal Vein Imaging

Objective:Using contrast-enhanced Multi-detector computed tomography（MDCT）to evaluate the detective rate of right adrenal vein（RAV）under different acquisition phases as well as evaluate its image quality.Under the premise of satisfying the detective rate of RAV,the radiation dose of RAV imaging by different scanning techniques was evaluated by changing the scanning period,reducing the tube voltage and tube current.Method:A total of 124 patients were enrolled in the study who were suspected as primary aldosteronism and requiring a contrast enhanced CT examination on adrenal glands.Four patients were excluded according to the exclusion criteria（BMI≥25kg/m²）,so that the rest 120 patients were divided equally into three groups.Group A was a control group with conventional tube voltage of 120kV and automatic mA.It was divided into A₁,A₂ and A₃ groups according to arterial phase,portal venous phase and parenchymal phase.Group B was a experimental group with conventional tube voltage of 120kV and automatic mA,which was divided into B₁,B₂,and B₃ groups according to arterial phase,late arterial phase and portal venous phase.Group C was a low-dose experimental group with a tube voltage of 100 kV and a tube current of150mA only in the second phase,the remaining scanning parameters and methods,as well as grouping method,were the same as group B.Part 1:Two imaging physicians used double-blind method to score the right adrenal vein images of the group A and B,respectively.The subjective scores of the images of groups A and B were statistically analyzed,and the CT values of the right adrenal vein（RAV）,the right adrenal gland（RAG）,and the fat of anterior abdominal wall at different scan phases were measured.Part 2:The relevant objective evaluation parameters of group C were measured and calculated,and the subjective and objective evaluations of the three groups were compared.Calculate and compare the difference between C₁ and C₂ in effective radiation doses.Statistical analysis was performed using SPSS 19.0 software.P<0.05 was considered statistically significant.Results:Part 1:The A₂ and B₂ groups were the best period of RAV detective rate in group A and B respectively.The detective rate and subjective score of B₂ were significantly higher than that of A₂,which the difference was statistically significant（H=6.38,P<0.05）.The objective scores,including the CT value of RAV,SNR,CNR of the B₂group were higher than those of the A₂ group（t/t’=-5.59,-2.85,-3.27,P<0.05）.Part 2:The subjective scores of the A₂,B₂,C₂ images were statistically significant（H=7.18,P<0.05）.Difference of subjective scores between B₂ and A₂ was statistically significant（t=-18.03,P<0.05）.The objective scores,including the CT value of RAV and RAG,background noise,SNR,CNR of the A₂,B₂,C₂ images were statistically significant（F=18.77,18.86,1.90,5.03,3.10,P<0.05）.The CT values of RAV,RAG and background noise of the C₂ group were higher than those of the B₂group（t=56.85,26.48,2.00,P<0.05）.The radiation dose comparison showed that the dose length production（DLP）and effective radiation dose（E）was 46.20%and45.52%lower in the low-dose group（C₂）than the conventional dose group（C₁）,which the difference was statistically significant（t=12.30,12.19,P<0.05）.Conclusions:Part 1:The right adrenal vein shows a higher detective rate in the late arterial phase than in the venous phase.Part 2:Using MDCT scanning technique with low tube voltage and low tube current of 100 kV-150 mA,the detection rate of right adrenal vein can reach 95%in the late arterial phase,and the effective radiation dose can be reduced about 45.52%on the basis of ensuring image quality.This study is helpful for physicians to estimate the location of RAV before AVS,as well as improving the success rate of AVS.