Abstract: Objective  To analyze the influence of contrast medium dosage on the enhancement of coronary artery and coronary venous sinus in patients with coronary heart disease of different severity during CT coronary angiography, and to explore the diagnostic value of CT coronary angiography for coronary heart disease and the application of contrast medium in enhanced scanning.
  Methods  Ninety-eight patients detected by Philips 256-slice spiral CT coronary angiography were divided into group A(ejection fraction≥50%, n=58) and group B(ejection fraction<50%, n=40) according to the echocardiography reports. Each group was further divided into four groups by random number table method, 29 cases in group A1, 29 cases in group A2, 20 cases in group B1 and 20 cases in group B2. At the time of scanning, the dosage of contrast agent in group A1 and B1(according to body weight) was 0.7 mL/kg; the dosage of contrast agent in group A2 and B2(according to body weight) was 0.8 mL/kg; the maximum CT values of ascending aorta, proximal left anterior descending branch, distal right coronary artery, main left coronary artery and coronary sinus were measured after injection of contrast agent in four groups, and the dosage and injection rate of contrast agent in four groups were also counted. Scanning time, delay time and image quality of four groups were scored, and the values of the above indexes in each group were compared.
  Results  ①The overall difference of the 4 groups with the maximum CT value of the proximal anterior descending branch and the distal right coronary artery was statistically significant(P＜0.001). Pairwise comparison showed that there was no significant difference between the A1 group and the A2 group, while there were statistically significant differences in other groups. ②The overall difference of the 4 groups with the maximum CT value of coronary venous sinus was statistically significant(P＜0.001). Pairwise comparison showed that there were statistically significant differences among all groups. ③The overall difference of image quality scores in 4 groups was statistically significant(P＜0.001). Pairwise comparison showed that there was no significant difference between A1 group and A2 group, while there were statistically significant differences in the other groups.
  Conclusion  ①In patients with normal cardiac function, the use of low-dose contrast agents(0.7 mL/kg) did not impair the quality of coronary artery imaging. For patients with reduced cardiac function, low-dose contrast agents can reduce the quality of coronary artery imaging. ②Reducing the amount of contrast agent will reduce the CT maximum value of coronary venous sinus（P＜0.05）. With the same dose of contrast agent, the maximum CT value of coronary venous sinus in normal cardiac function group was lower than that in cardiac insufficiency group.

Key words: coronary disease； coronary angiography, diagnosis