Dual-source CT coronary angiography in patients with medium and low heart rate: imaging quality and radiation doses at a low tube voltage

Objective: To evaluate the imaging quality and radiation doses of dual-source computed tomography (DSCT) coronary angiography at a low tube voltage in patients with medium and low heart rate. Methods: Eighty-five patients [heart rate (HR) < 91 beats per minute (bpm); body mass index (BMI) 17.51-30.00 kg/m2] suspected of coronary artery disease received retrospectively ECG-gating coronary angiography with dual-source CT scanner (Somatom Definition, Siemens) at a tube voltage of 100 kVp. For all patients, no beta-blocker was used before CT scan. According to the HR, the patients were divided into three groups: Group A, HR ≤ 59 bpm, n=27; Group B, HR 60-69 bpm, n=29; Group C, HR ≥ 70 bpm, n=29. All images were transferred to a workstation for postprocessing. 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 (ED) 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 HR on image quality and. radiation doses of coronary artery was analyzed. Results: The value of pitch in Group A, Group B and Group C was 0.241±0.025, 0.286±0.034 and 0.335±0.036, respectively. The mean score of imaging quality of coronary artery segments in Group A, Group B and Group C was 4.78±0.26, 4.66±0.56 and 4.70±0.46, respectively. The value of CTDIvol in Group A, Group B and Group C was (18.06±5.16), (19.62±7.15) and (17.50±7.13) mGy, respectively. The value of ED in group A, Group B and Group C was (4.23±1.16), (4.59±1.75) and (4.12± 1.39) mSv, respectively. There was statistical difference in value of pitch among the three groups (F= 60.00, P=0.00). There were no statistical difference in score of imaging quality, CTDIvol and value of ED among the three groups (F=0.53, P=0.59; F=0.83, P=0.44; F=0.86, P=0.43). Conclusion: Medium and low HR have little influences on image quality of dual-source CT coronary angiography at a low tube voltage. When the auto ECG-gating is selected, there is little influence on radiation dosage as well. (authors)