Impact Of Heart Rate And Heart Rate Variation On Image Quality In 64-slice CT Coronary Angiography With Prospective ECG-Gating

Objective1.Using a pulsating cardiac phantom to evaluate the effect of heart rate (HR) and HR variation on image quality in 64-slice CT coronary angiography (CTCA) with prospective ECG-gating. To compare image quality between prospective and retrospective ECG-gating CTCA. The aim is to explore how to use prospective ECG-gating technique.2.When HR<65 beats/minute(bpm), to confirm the effect of HR and HR variation on image quality of prospective ECG-gating CTCA though the clinic research.Material and Methods1.An adjustable pulsating cardiac phantom(GE)containing was scanned using 64-slice CT scanner with cardiac pulsating rates of 45,50,55,60,65,70,and 75bpm.and HR variations of 0,2,4,6,8,and 10 bpm respectively. The quality of images reconstructed with different R-R phase was evaluated by three radiologists on a 4-point scale. To analyze the best reconstruction phase by Friedman test and SNK test. Effects of HR and HR fluctuation on image quality of prospective ECG gating CTCA were analyzed by using Spearman correlation. Mann-Whitney U test was used to compare image quality between prospective and retrospective ECG-gating CTCA.2.80 patients were scheduled for CTCA using prospective ECG triggering.β-blockers were oral administered if necessary to achieve a target HR<65 bpm before scanning. The image quality of all coronary segments was rated on a 4-point scale by two independent readers. Effects of HR and HR variability on image quality were analyzed by using Pearson correlation.Results1.The image quality using prospective ECG-gating was inversely related to HR. When HR≤60bpm, no significant correlation was found between image quality and HR fluctuation(≤10bpm),and the quality of all the images reconstructed with 75%R-R phase was diagnostic satisfactory. When HR≥65bpm, there was significant correlation between HR fluctuation and image quality. When HR=50bpm, HR fluctuation=10bpm and HR=70bpm, HR fluctuation=2,4bpm, image quality scores with the prospective ECG-gating CTCA were significantly higher than that with the retrospective ECG-gating. When HR=70bpm, HR fluctuation=10bpm, there was a significant improvement in image quality of retrospective ECG-gating compared with that of the prospective ECG-gating.2.80 patients completed CTCA.1039 coronary segments were evaluated, and the imaging quality of 1003 segments (96.54%) was diagnostic. Image quality of the RCA, the LCX, and overall coronary segments was inversely related to HR(P< 0.05), while no significant correlation was found between HR and image quality of the LAD and the LM. There was no significant correlation between HR variability and image quality of each coronary artery or overall segments.Conclusion1.When HR≤60bpm and HR fluctuation≤10bpm, there is no significant corrclation between HR fluctuation and image quality. In this case, it is suggested to apply prospective ECG gating CTCA instead of retrospective ECG gating. Moreover, the value of padding can be setted as 0 for decreasing radiation dose sharply. When HR≥65bpm, it's better to use retrospective ECG gating CTCA.2.Prospective ECG-triggering 64-slice CTCA can reduce the radiation dose. In patients whose HRs<65 beats/min, there is no significant impact of HR variability on image quality, while HR still plays a key role in obtaining diagnostic image quality.