Initial study of optimal reconstruction windows in 320-detector row CT coronary angiography / 中华放射学杂志

ABSTRACT

ObjectiveTo investigate the optimal reconstruction windows for coronary angiography using 320-detector row dynamic volume CT (DVCT) and evaluate their effects on image quality,radiation dose and diagnostic accuracy.MethodsFrom 77 patients [mean heart rate (70 + 13) bpm,range46-102 bmp] were scanned with retrospective ECG-gating 320-detector row DVCT.The relationship between heart rate and optimal reconstruction windows was analyzed.From 53 patients [mean heart rate ( 75 ±11 ) bpm,range57-114 bpm] were scanned with prospective ECG-gating 320-detector row DVCT.The effects of prospective ECG-gating on image quality,radiation dose and diagnostic accuracy were evaluated.Friedman test was performed for image quality scores in random groups.Linear regression and Spearman correlation were performed to test bivariate data.ResultsThe proportion of systolic duration in the cardiac cycle increased significantly with higher heart rate (r =0.78,P ＜0.01 ).The image quality in systolic and diastolic phases were significantly influenced by heart rate ( r =0.38,0.82 ; P ＜ 0.01 ).According to the regression analysis of image quality score in different heart rate groups,the optimal reconstruction windows were determined as followedwhen heart rate was ＜ 70 bpm,the optimal reconstruction windows should be preset at 65％-80％ ; 70 to 80 bpm,70％-85％ ; 81 to 90 bpm,70％-90％ ; ＞90 bpm,35％-50％.Compared with retrospective ECG-gating,prospective ECG-gating which preset reconstruction windows according to the phases mentioned above,could decrease radiation dose [(6.1 ± 3.8 )vs (12.4 ± 7.0) mSv],without deteriorating the image quality (t =6.5,P ＜ 0.01 ).However,in higher heart rate,the radiation dose of prospective ECG-gating DVCT was still higher ( r =0.64,P ＜ 0.01 ).ConclusionsDVCT can provide high image quality in a wide range of heart rate with prospective ECG gating.It is still recommended to control heart rate strictly since the radiation dose increases significantly in high heart rate.