The application of dual-source CT coronary angiography in low tube voltage setting and the influence of heart rate on image quality and radiation doses

Objective To evaluate the application value of dual-source CT coronary angiography in low tube voltage setting and the influence of heart rate on image quality and radiation doses.Methods 323 patients suspected of coronary artery disease received retrospective ECG-gating coronary angiography with dual-source CT scanner,who were divided into low tube voltage group (100 kVp,n =201) and conventional voltage group (120 kVp,E group,n =122).No beta-blockers were taken before CT scan.All patients in low tube voltage group were divided into four groups according to the heart rate (HR):group A,HR≤59 beats per minute (bpm),n =50; group B,60≤HR ＜69 bpm,n =64; group C,70≤HR ＜91bpm,n =62;group D,HR ≥ 91 bpm,n =25.All images were transferred to a workstation for further processing.The best R-R interval reconstruction images of all groups were evaluated.The value of pitch,CT volume dosage index(CTDIvol),dose length product(DLP) and effective dose(E)were recorded.The pitch,the score of imaging quality of coronary artery segments and the radiation dose were compared with One-Way ANOVA.The influence of heart rate on image quality and radiation doses of coronary artery was analyzed.Results The value of pitch in groups A-D was 0.24 ± 0.03,0.29 ± 0.04,0.33 ± 0.05,0.38 ± 0.06,respectively,with statistical difference (F =62.57,P ＜ 0.05).The value of CTDIvol in groups A-E was (21.59±7.97),(20.24±6.03),(18.23±7.55),(18.14 ±5.75),(38.62±16.21)mGy,respectively,with statistical difference (F =85.16,P ＜ 0.05).The value of E in group A-E was (5.31 ±2.18),(4.85 ±1.70),(4.49 ± 1.86),(4.37 ±1.50),(8.75 ± 4.07) mSv,respectively,with statistical difference(F =44.83,P ＜ 0.05).The image score was (4.65 ±0.46),(4.55 ± 0.53),(4.55 ±0.53),(4.47 ±0.72),(4.66 ± 0.44) (F =1.89,P ＞ 0.05).Conclusions No beta-blockers was taken before CT scan,and a high quality image could be acquired by using dual-source CT coronary angiography in low tube voltage setting(100 kVp).When the auto ECG-gating is selected,medium and low HR have little influences on radiation dose,while the radiation dose could be decreased significantly at higher HR,but the possibility to obtain the high quality image decreased. Key words: Heart rate; Coronary artery; Tomography; Radiation dosage