ABSTRACT
Objective:To explore the application of energy spectrum CT single energy combined with adaptive statistical iterative reconstruction-Veo (ASIR-V) for optimizing inferior vena cava imaging.Methods:Thirty patients with negative diagnosis or minimal inferior vena cava lesions who underwent CT venography (CTV) of inferior vena cava in the Second Hospital of Harbin Medical University from August 2021 to April 2022 were enrolled in the study, including 11 males and 19 females with the age of (55.4±8.8) years and the body mass index of (23.2±2.8) kg/m2. The mixed energy group images and 5 single energy groups of 50, 55, 60, 65 and 70 keV images were reconstructed from the images in the inferior vena cava phase. The subcutaneous fat noise, CT values, signal to noise ratio (SNR) and contrast to noise ratio (CNR) for each segment of the inferior vena cava in 5 sets of single-energy images were measured and evaluated subjectively to determine the best single energy level. The images were reconstructed by combining different weight ASIR-V (20%, 30%, 40%, 50%, 60%, 70% and 80%) algorithms, and images from different weight groups and mixed energy groups were evaluated objectively to determine the best ASIR-V weights which was matched with the best single energy level. All images were scored subjectively by 2 senior radiologists based on image noise, uniformity of vessel filling, sharpness of vessel margins and diagnostic confidence.Results:There were significant differences in subcutaneous fat noise and objective evaluation indexes of each segment of inferior vena cava among the monoenergetic groups (all P<0.05), each objective evaluation index increased with the decrease of energy level, the maximum value was obtained in the 50 keV group. The subjective scores of the 5 groups were consistent by the 2 radiologists(all κ≥0.75). The highest subjective scores were obtained in the 60 keV group, the best single energy level is 60 keV in a comprehensive analysis. The differences in objective evaluation indicators among the 7 groups of best single energy combined with different weights ASIR-V image group and the mixed energy group were all statistically significant (all P<0.01). Image noise decreased with increasing ASIR-V weights for different weight groups, all differences among groups were statistically significant (all P<0.01), and the minimum noise was minimal in 80% weight group. There was no significant change in CT value of each segment of inferior vena cava (all P>0.05). The SNR and CNR of each segment of inferior vena cava increased, all differences among groups were statistically significant (all P<0.01), and the SNR and CNR of 80% weight group was the highest. The subjective scores of the 8 groups were consistent evaluated by the 2 radiologists (all κ≥0.75), and the subjective score of 60% weight group was the highest, 60% was the best ASIR-V weight for matching 60 keV in a comprehensive analysis. Conclusions:The study indicates that the best energy level for optimizing energy spectrum CT single energy imaging of the inferior vena cava is 60 keV, on the basis of which the best weighting for combined ASIR-V is 60%.