【Objective】 To investigate the value of deep learning image reconstruction (DLIR) in improving image quality and reducing beam-hardening artifacts of low-dose abdominal CT. 【Methods】 For this study we prospectively enrolled 26 patients (14 males and 12 females, mean age of 60.35±10.89 years old) who underwent CT urography between October 2019 and June 2020. All the patients underwent conventional-dose unenhanced CT and contrast-enhanced CT in the portal venous phase (noise index of 10; volume computed tomographic dose index: 9.61 mGy) and low-dose CT in the excretory phase(noise index of 23; volume computed tomographic dose index: 2.95 mGy). CT images in the excretory phase were reconstructed using four algorithms: ASiR-V 50%, DLIR-L, DLIR-M, and DLIR-H. Repeated measures ANOVA and Kruskal-Wallis H test were used to compare the quantitative (skewness, noise, SNR, CNR) and qualitative (image quality, noise, beam-hardening artifacts) values among the four image groups. Post hoc comparisons were performed using Bonferroni test. 【Results】 In either quantitative or qualitative evaluation, the SNR, CNR, overall image quality score, and noise of DLIR images were similar or better than ASiR-V 50%. In addition, the SNR, CNR, and overall image quality scores increased as the DLIR weight increased, while the noise decreased. There was no statistically significant difference in the distortion artifacts (P=0.776) and contrast-induced beam-hardening artifacts (P=0.881) scores among these groups. 【Conclusion】 Compared with the ASiR-V 50% algorithm, DLIR algorithm, especially DLIR-M and DLIR-H, can significantly improve the image quality of low-dose abdominal CT, but has limitations in reducing contrast-induced beam-hardening artifacts.

【Objective】 To investigate the value of abdominal aortic combined with routine one-stop triple rule-out computed tomography angiography (TRO-CTA) in the examination of patients with acute chest pain. 【Methods】 A total of 1 482 patients with nontraumatic chest pain were included in this retrospective study. Of them 414 patients underwent the conventional TRO-CTA scanning while 1 068 patients underwent TRO-CTA that included the abdominal aorta (TRO-CTAwAA) under the request of clinicians. All scanning parameters were the same, except the scanning range for the third phase in TRO-CTA: conventional TRO-CTA covered only the thoracic aorta, while TRO-CTAwAA extended to the entire aorta. Patient etiology was investigated and the detection rates of major vessel abnormalities (aortic dissection, aneurysm, penetrating ulcer, intramural hematoma, vascular occlusion, and thrombosis) between the two groups was compared using chi square tests. The radiation dose (CTDIvol and DLP) and scanning time between the two groups were compared using analysis of variance (ANOVA). 【Results】 The TRO-CTAwAA had significantly higher detection rate of major artery abnormalities than the TRO-CTA group (35.1% vs. 4.8%, P<0.001). In the TRO-CTAwAA group, 26.5% of the vascular anomalies were detected in both the thoracic and abdominal aortas, and another 8.6% were seen only in the abdominal aorta. With regard to the radiation dose between the two groups, the total DLP was significantly higher in the TRO-CTAwAA group than in the conventional TRO-CTA group (P<0.001). The two groups did not significantly differ in scanning time (P=0.410). 【Conclusion】 TRO-CTA with scan range including the abdominal aorta significantly improves the detection rate for major vessel abnormalities in patients with chest pain without increasing the examination process.