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Objective: To study the effect of different triggering thresholds on the quality of pulmonary artery CT angiography (CTA) images. Materials and Methods: A prospective study included 112 patients with suspected pulmonary embolism admitted to Tinglin Hospital in the Jinshan District of Shanghai between December 2021 to April 2023. Among them, there were 49 males and 63 females aged between 37 and 93 years, with an average age of 64.28 years. Patients were randomly assigned to three groups based on trigger thresholds. Group A included 38 cases with a trigger threshold of 120 HU, Group B included 37 cases with a trigger threshold of 200 HU, and Group C included 37 cases with a trigger threshold of 250 HU. There were no statistically significant differences in gender, age, height, or weight among the three groups. One-way ANOVA was used to compare the CT values and subjective image quality scores of the superior vena cava, main pulmonary artery, left and right pulmonary arteries, and right pulmonary vein among the three groups. Result: There were no statistical differences in the CT values of the main pulmonary artery and left and right pulmonary arteries among the three groups, but there were statistical differences in the CT values of the superior vena cava and right pulmonary vein. There was a statistical difference in the subjective score of image quality among the three groups; the subjective evaluation of the obtained image quality between the two physicians was highly consistent (κ=0.78). Conclusion: When the triggering threshold of pulmonary artery CTA is 200 HU, it can not only ensure the concentration of pulmonary artery trunk CT value meets the clinical diagnosis, but also ensures that the contrast agent is fully injected into the 5~6 grade branches, leading to less retention of superior vena cava, weak pulmonary vein development, and the highest image quality of pulmonary artery CTA.

Objective: To explore the influence on the image quality of head and neck CTA under different tube voltages. Materials and methods: A total of 67 patients with clinically suspected head and neck vascular diseases in Tinglin hospital from September 2021 to January 2022 were collected as the research objects, including 37 males and 30 females, with an average age of 68.94. According to the applied tube voltage, the patients were randomly assigned into groups A, B and C. There were 23 cases of 120 kV in group A, 24 cases of 100 kV in group B and 20 cases of 80 kV in group C. Single factor ANOVA test was used to compare the CT value, SD value, SNR, CNR of aortic arch, internal carotid artery, M1 segment of middle cerebral artery and sternocleidomastoid muscle among the three groups, and furthermore the subjective score of image quality, TDLP and ED. Kappa test was used to evaluate the consistency of subjective scores of the two physicians. Results: There were statistical differences in CT and SD values of aortic arch, internal carotid artery and M1 segment of middle cerebral artery among the three groups; The CT and SD values of aortic arch, internal carotid artery and M1 segment of middle cerebral artery increased with the decrease of tube voltage, with an increase range of 15%～55%. There was no statistical difference in SNR and CNR among the three groups; There was statistical difference in subjective score of image quality among the three groups; Group B > group A > group C, and group B showed the highest score; the kappa value of the subjective score of the two phsicianss=0. 80, which was highly consistent; There were statistical differences in TDLP and ED among the three groups, TDLP and ED decreased with the decrease of tube voltage, with the decrease ranges of 25% and 39%. Conclusion: According to the requirements of CT radiation dose diagnosis reference level, 100 kV is the best tube voltage condition for head and neck CTA.