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Objective To study the effect of different rate of hear on the image quality and the dose of radiation for the coronary artery by apply dual-source CT(DSCT)adaptive prospective ECG gated sequences were Scanning for the free heart rate of coronary angiography(CTCA).Methods 150 patients with free heart rate(heart rate variability is less than or equal to 5 times)suspected coronary artery disease were divided into A,B,C three groups according to the level of heart rate.50 cases in each group,A<75bpm; 75bpm≤B≤90bpm;C>90bpm;DSCT adaptive adaptive ECG gated sequences scanning was performed in all the patients.Among them,15 patients in each group were underwent conventional coronary angiography(CAG)in 1 week successively.After all of patients were adapted by the coronary angiography(CTCA),the coronary artery segments evaluation rate and image quality score image quality and radiation dose were analyzed through one-way analysis of variance.With the gold standard in CAG, sensitivity,specificity,positive predictive value and negative predictive value of CTCA diagnosis of coronary artery stenosis were evaluated in three groups respectively.and Kappa test was used for comparison CTCA with CAG in diagnosis consistency of coronary artery stenosis degree. Result A,B,C three groups of coronary angiography(CTCA),the coronary artery evaluation rate were 97.8%(752/769)、96.9%(749/773)、95.2%(731/768),there was no statistically significant(P>0.05);CTCA image quality score of three groups were(4.7±0.8)、(4.6±0.9)、(4.5±0.8)respectively,there was no statistically significant(P>0.05).the effective radiation dose were(6.0±0.31)、(5.1±0.33)、(4.1±0.33)mSv respectively in three groups,and the effective radiation dose had statistically significant(P<0.05).Sensitivity,specificity,positive predictive value and negative predictive value of CTCA in diagnosis of coronary artery stenosis in three groups were 86.0%、94.1%、83.1%、95.2%in group A and 90.1%、94.9%、84.2%、97.1%in group B and 85.2%、96.4.0%、89.7%、94.7%in group C respectively.CTCA and the CAG in the diagnosis of coronary artery stenosis degree is consistent(Kappa=0.791、0.833、0.829).Conclusion The dual-source CT adaptive ECG gated sequences scanning technique can be used in CTCA of patients with free heart rate, yielding higher image quality,accurate assessment of coronary artery stenosis degree,and significantly reducing the radiation dose with increasing level of heart rate at the same time .