Effect Of Optimal Window Setting Combined With Iterative Model Reconstruction Technique On Abdominal CT Image Quality In Patients With Cirrhosis

Objective:To investigate the impact of optimal window setting combined with iterative model reconstruction(IMR)technique on the quality of abdominal CT images in patients with cirrhosis and the optimal window setting.Methods:The imaging data of 70 patients with cirrhosis who received non-contrast and enhanced upper abdominal CT scan in Baoding NO.1Central Hospital from November 2021 to July 2022 were retrospectively analyzed.The fourth generation iterative reconstruction(i Dose~4)technique and IMR technique were used to reconstruct the original images in the arterial phase,divided into group A(i Dose~4 reconstructed images)and group B(IMR reconstructed images),and the window widths of group B images were adjusted to B1(250HU),B2(200HU),B3(175HU),B4(150HU),B5(125HU),B6(100HU),B7(50HU)seven sets of images.First,the CT values,background noise,signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of liver nodules and liver tissue adjacent to the lesion in each group of images were compared to complete an objective evaluation of the image.Secondly,the image quality of each group was subjectively evaluated separately,including image contrast,subjective image noise,lesion saliency and overall image quality,and the optimal window width was preferred.Finally,the number of lesions found in the IMR reconstructions with the optimal window setting,the IMR reconstructions with the conventional abdominal window setting and the i Dose~4 reconstructions were compared.One-way ANOVA was used to compare the objective image quality assessment data,and the Kruskal-Wallis H test was used to determine whether the differences in subjective image quality scores were statistically significant.Results:Statistical analysis showed that:(1)Background noise and subjective image noise of group A were greater than those of group B1,and CNR value,SNR value,image contrast,lesion conspicuity and overall image quality score were all lower than those of group B1,with statistically significant differences(P<0.05).The differences in the CT values of the lesion and the CT values of the liver tissue adjacent to the lesion measured in each image group and the objective evaluation of the image quality in the B1-B7 group were not statistically significant(P>0.05).(2)Comparing the subjective image quality scores of the B1-B7 subgroups,it was found that when the window width was reduced from 250HU to 100HU,the image contrast and subjective image noise increased with every 50HU reduction,but the lesion conspicuity and overall image quality of the B4 group images were greater than those of the B1,B2,B6 and B7 groups,with statistically significant differences(P<0.05).(3)Comparison of the number of lesions:group A was less than group B1 and less than group B4,with statistically significant differences(P<0.05).Conclusions:1.Compared with i Dose~4 reconstruction technology,IMR technology can reduce image noise and improve the image quality of abdominal CT scanning.2.Choosing a smaller window width can improve the contrast resolution of the image and improve the detection rate and diagnostic accuracy of small lesions with low contrast.3.It is suggested that 125HU～175HU、50HU should be used as the optimal window setting for IMR reconstruction of abdominal CT scan in patients with cirrhosis.