The Evaluation of Imaging Quality of Abdominal Vein by Combining Spectral CT Optimal Monotromatic Imging and ASiR Technique

Objective: To compare the imaging quality of different levels of the adaptive algorithm of iterative reconstruction (ASiR) in abdominal venous optimal single energy image to optimize imaging parameters of abdominal vein. Materials and Methods: Retrospective analysis was performed on 30 patients who underwent CT upper abdomen enhancement scan. All the subjects were scaned with spectral model and optimal single energy images were calculated using postprocessing workstation, and then reconstructed with ASiR 30%, ASiR 40% and ASiR 50% algorithm respectively. Finally, three group images of different ASiR levels were acquired. The CT value, image noise, contrast noise ratio (CNR) and signal noise ratio (SNR) of all abdominal vein were compared among the images of the three single energy groups and one mixed energy group by using single factor analysis of variance (ANOVA). The data of four groups were subjectively evaluated by two professional diagnostic physicians using double blind method. Results: The original spectral CT data were processed to acquire the 65 keV images, which were reconstructed with 30% ASiR, 40% ASiR and 50% ASiR, respectively. Together with the mixed energy group, finally four groups were obtained. There were statictically significant differences of CT value, image noise, CNR and SNR between the mixed energy group and the other three single energy groups (P<0.01). There was no significant difference in CT value among 30% ASiR group, 40% ASiR group and 50% ASiR group (P>0.05). For the portal vein trunk, mesenteric vein and splenic vein, there were significant differences of image noise, CNR and SNR between the 30% ASiR group and the 50% ASiR group (P<0.05), while no differences of that parameters between the 30% ASiR group and the 40% ASiR group, as well as 40% ASiR group and the 50% ASiR group (P>0.05); For the inferior vena cava trunk, the left renal vein, the right renal vein, the left hepatic vein, the middle hepatic vein and the right hepatic vein, there were significant differences of image noise and CNR between the 30% ASiR group and the 50% ASiR group (P<0.05), while no differences of that parameters between the 30% ASiR group and the 40% ASiR group, as well as 40% ASiR group and the 50% ASiR group (P>0.05); There were significant differences of SNR among the three groups (P<0.05). Conclusion: For the abdominal veins, the imaging quality of the optimal single energy (65keV) +40% ASiR is better than that of the 65keV+30% ASiR, 65keV+50% ASiR and the mixed energy group, which can be widely used in clinical abdominal venous angiography.