目的:了解扇区重建技术在冠状动脉CT成像中的应用价值.方法:58例受检者,根据心率分为3组,A组,心率＜75次/min,单扇区重建；B组,心率75～94次/min,双扇区重建；C组,心率95～115次/min,四扇区重建.分别测量冠状窦开口处增强前后CT值的变化,并计算强化率,同时测量受检者的受辐射剂量CTD和DLP值.对三维冠状动脉重建图像质量按5个等级进行主观评分:5分无伪影；4分轻微伪影,仅主干的某一段轻微模糊,诊断不受影响；3分为中等伪影,某一支冠状动脉主干的1/2以上模糊,但可以诊断；2分为严重伪影,某一支冠状动脉主干全长均模糊不清或不连续,诊断受限；1分为冠状动脉主干不能识别,不能作出诊断.其中4分以上因伪影的干扰较少定为优良.结果:①主观评分:A组:共29例,优良率为100％；B组:共20例,优良率为85％;C组:共9例,优良率为56％；②客观评估:3组病例的强化均值、强化率、CTD和DLP值之间均存在显著差异(P＜0.05),单扇区扫描获得的图像的强化效果最佳,且受检者在检查过程中的所受到的辐射剂量最小.结论:受检者在检查前服用β受体阻滞剂控制心率,并采用单扇区重建技术能获得理想的冠状动脉诊断图像.%Objective:To evaluate the effect of different segment image reconstructions for different heart rates(HRs) on 64-multislice computed tomographic (MSCT) coronary angiography. Methods: Fifty-eight patients were categorized into 3 groups based ondifferent sinus rhythms heart rate (HR). Group A, HR<75 beats per minute, single-segment image reconstruction) Group B, HR 75-94 beats per minute, two-segment image reconstruction) Group C, HR 95-115 beats per minute with four-segment image reconstruction. Mean attenuation values of the coronary sinus were measured before and after contrast enhancement and the enhancement ratio were also calculated. Weighted CT dose indexes (CTDI) and dose-length product (DLP )were obtained for all protocols and the image quality were graded on a 5-point confidence scale,Grades 4 and 5 were accepted as good and excellent for the image quality. Results: The ratio of good and excellent image quality were 100% (29/29) for group A, 85%(17/20) for Group B and 56% (5/9) for Group C. The values of mean attenuation, enhancement ratio, CTDI and DLP showed significant difference among the 3 groups(P<0. 05). The best image quality and the least radiation dose were achieved at single-segment image reconstruction. Conclusions: Oral administration of β-blockers to control patients' HR and use of single-segment image reconstruction are very important to get the best diagnostic image in 64-MDCT coronary angiography.
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