| Objective: This study explores the value of applying individualized triggering threshold to CT coronary angiography in patients with different heart rate.It evaluates the influence of heart rates and triggering thresholds on the image quality of coronary angiography,and explores the optimal triggering threshold under different heart rates.Methods: 600 cases of patients with 256-slice spiral CT coronary angiography are screened,divided into four groups according to the heart rate speed,150 patients in each group.Group A(heart rate ≤ 70 beats / min);group B(70 beats / min <heart rate ≤ 80 beats / min);group C(80 beats / min <heart rate ≤ 90 beats / min);group D(heart rate> 90 beats / min).According to the set triggering threshold(80 HU,100 HU,120 HU,140 HU,160HU),each group is divided into five subgroups,30 patients in each subgroup.The excitation levels selected as the descending aorta in horizontal alignment with the origin of pulmonary artery trunk.The contrast mediums injected using the heart module of the Medrad Syringe P3 T.When the CT value of the excitation level reaches the threshold,it triggers scanning.The CT value and SD value of the right coronary artery opening,the left coronary artery opening,the proximal left anterior descending branch,the proximal left circumflex branch are measured.The image quality is scored though double-blind method by two radiologists.Results: Group A: Coronary artery CT value of Subgroup A1(80HU)is statistically significant compared with the other four subgroups,and there are no statistically significant differences between the four subgroups.The SD values(Image noise)of the right coronary artery opening,left main trunk opening,proximal left anterior descending artery are statistically significant.The SD value(Image noise)of the subgroup A4(140HU)is the smallest,and the SD value(Image noise)of proximal left circumflex artery of subgroup 1(80HU)is statistically significant compared with the other four subgroups,and there are no statistically significant differences between the four subgroups.Group B: Coronary artery CT value of Subgroup B1(80HU)is statistically significant compared with the other four subgroups,and there is no statistically significant difference between the four subgroups.The SD values(Image noise)of subgroups of the proximal left anterior descending artery are statistically significant,and the SD value(Image noise)of the subgroup B3(120HU)is the smallest.The SD value(Image noise)of the left main trunk opening of the subgroup B1(80HU)is statistically significant compared with the other four subgroups,and there is no statistically significant difference between the four subgroups.The SD values(Image noise)of the right coronary artery opening and the proximal left circumflex artery are not statistically significant.Group C: Coronary artery CT value of Subgroup C5(160HU)is statistically significant compared with the other four subgroups,and there is no statistically significant difference between the four subgroups.The SD values(Image noise)of the right coronary artery opening and the proximal left circumflex artery are not statistically significant.The SD values(Image noise)of the left main trunk opening and the proximal left anterior descending branch are not statistically significant.And the SD value(Image noise)of the subgroup C2 is smallest.Group D: The subgroup D1(80HU)and subgroup D2(100HU)have no statistically significant differences.Subgroup D1(80HU)is statistically significant compared with the subgroup D3 to subgroup D5,but the subgroup D3 to subgroup D5 have no statistically significant difference.The SD value(Image noise)of the right coronary artery opening and the left main trunk opening are statistically significant,and the SD value(Image noise)of the subgroup D1(80HU)is the smallest.The SD values(Image noise)of left anterior descending branch proximal and left circumflex branch proximal of the subgroup D1(80HU)are statistically significant compared with the other four subgroups,and there is no statistically significant difference between the four subgroups.The CT value,SD value(Image noise)and image score of coronary artery in group D are statistically significant compared with the other three groups(group A,group B,group C).There is no significant difference between the three groups.The CT value of group D is the lowest,the SD value(Image noise)is the highest,and the image score is the lowest.Conclusion:1 With the increase of heart rate,the scan triggering threshold decreased accordingly.When the heart rate of patients≤70beats/min,the 140 HU threshold triggers scan.The SD value(Image noise)of right coronary artery opening,left main opening,proximal left anterior descending branch is minimal and the image quality is optimal.When 70 beats/min<heart rate≤80 beats/min,the 120 HU threshold triggers scan.The SD value(image noise)of left main trunk opening,proximal left anterior descending branch is minimal and the image quality is optimal.When 80 beats/min<heart rate≤90beats / min,the 100 HU threshold triggers scan,and the SD value(image noise)of right coronary artery opening,left main trunk opening,proximal left anterior descending branch is minimum,and the image quality is optimal.When heart rate>90 beats/min,the 80 HU threshold triggers scan,the SD value(image noise)of right coronary artery opening,left main trunk opening,proximal left anterior descending branch,proximal left circumflex branch is minimal and the image quality is optimal.2 When the heart rate is greater than 90 beats/min,the CT value of each coronary artery is significantly reduced,the SD value(image noise)increases,the image quality decreases,and the image score is the lowest.But it is basically able to meet the diagnosis.3 The optimal scan trigger threshold is selected according to the heart rate.Because of its small range,it is recommended to combine the manual and automatic,trigger the scan as close as possible to the best threshold.So that it can get high quality image with good contrast,provide accurate information for the diagnosis. |
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