Effect Of Energy Spectrum CT Combined With Pre-ASiR-V And Post-ASiR-V On Image Quality And Radiation Dose Of Portal Vein Angiography

ObjectiveTo investigate the effect of spectral CT based on Revolution 256 row combined with Adaptive Statistical iterative Reconstruction V（ASi R-V）with different weights on image quality and radiation dose of portal vein angiography,in order to find the optimal pre-ASi R-V weights and post-ASi R-V weights.MethodPart I:Effects of energy spectrum CT combined with different pre-ASi R-V on image quality and radiation dose of portal vein angiographyPatients who underwent upper abdominal enhanced CT in our hospital from December 2021 to February 2023 were prospectively collected.A total of 192 patients who met the inclusion criteria were randomly divided into group A,B,C,D and F.All patients were scanned with spectral CT combined with pre-ASi R-V weight of 0%-50%（interval 10%）.The CT volume dose index and dose length product on the CT scan sheet were recorded,and the effect dose（ED）was calculated.The subjective evaluation of the images by two radiologists in a double-blind method was recorded.The CT value and standard deviation of the main portal vein,left and right branches and adjacent liver parenchyma were measured in all images.The CT value and standard deviation of all images were measured three times and averaged.The signal-to-noise ratio（SNR）and contrast-to-noise ratio（CNR）of the main portal vein and its left and right branches were calculated.After statistical analysis,the best pre-ASi R-V group was selected.Part II:Effect of different post-ASi R-V on image quality of portal vein angiographyThe best pre-ASIR-V weight（group F,50%pre-ASi R-V）images optimized in the first part were used to reconstruct F₀,F₁,F₂,F₃,F₄,F₅images with 0%-100%（interval20%）post-ASi R-V.The images of each group were subjectively scored and recorded by two senior radiologists in a double-blind method.The CT and SD values of the region of interest in each subgroup were measured in the same way as in the first part.The SNR values of liver parenchyma,main portal vein and its branches,and the CNR values of main portal vein and its branches were calculated.The objective and subjective image evaluation indexes were comprehensively analyzed to optimize the best post-ASi R-V group.Result Part I1.There was no significant difference in gender among all groups（X²=3.363,P=0.644）,and there was no significant difference in age and BMI among all groups（P>0.05）.The data of the six groups were basically consistent and comparable among all groups.2.The Effect Dose of group A,B,C,D,E and F were 5.81±0.76m Sv,5.50±0.41m Sv,4.86±0.35m Sv,4.05±0.48m Sv,3.50±0.35m Sv and 3.03±0.33m Sv,The ED decreased with the increase of pre-ASi R-V,and the effective radiation dose of group B,C,D,E and F was reduced by 5.3%,16.4%,30.3%,39.8%and 47.9%compared with group A.The difference of effective radiation dose among the five groups was statistically significant.Spearman rank correlation analysis showed that there was a negative correlation between ED and pre-ASi R-V weight:r_s=-0.924（P<0.01）.3.There was no significant difference in SNR,CNR,SD and subjective score of portal vein trunk,right and left branches among groups（P>0.05）.There was no significant difference in image background noise among groups A to F（P=0.971）.There was no significant difference in subjective evaluation between groups A and F（Z=1.674,P=0.795）.Part IIThe image background noise,vascular noise of the main portal vein and the left and right branches of the portal vein in each F₀-F₅subgroup decreased with the increase of post-ASi R-V,and the differences among the groups were statistically significant（P<0.05）.The SNR of liver parenchyma,main portal vein,left and right branches of portal vein and CNR of main portal vein,left and right branches of portal vein increased with the increase of post-ASi R-V,and the differences between groups were statistically significant（P<0.05）.The subjective score of group F₃was higher than that of other subgroups（F₀,F₁,F₂,F₄,F₅）,which was（4.65±0.60）,and the difference of subjective score among the six groups of F₀-F₅was statistically significant（Z=12.783,P<0.05）.ConclusionSpectral CT combined with 50%pre-ASi R-V and 60%post-ASi R-V for portal vein angiography can reduce the radiation dose of patients and obtain better image quality.