相对时间分辨率在临床64层MSCT冠状动脉成像中意义的初步探讨

The Effect of Relative Temporal Resolution in Clinical 64-MSCT Coronary Angiography

目的:评价临床64层MSCT冠状动脉成像中相对时间分辨率与图像运动伪影的关系,建立冠状动脉CTA成像的心率选择标准。方法:收集496例心功能基本正常患者的64层MSCT冠状动脉成像。应用单扇区方法重建心动周期多时相的横轴位薄层图像。选择右冠状动脉垂直段单个心动周期图像运动伪影最小的时相,记录相应心率和评价图像运动伪影情况。运动伪影评分分为5级。应用有效可靠性(ER)描述相对时间分辨率。对ER与图像质量的关系进行分析,得出不同图像质量要求下的ER域值,并比较是否满足ER要求病例间最佳重建时相的差异。结果:496例患者心率范围在43bpm至103bpm(平均65.99bpm±12.389bpm)。以评分3以上为合格图像质量标准,则ER大于81是检查成功的下限。如以评分4作为合格图像质量标准,则ER大于84为检查成功的下限。不能满足ER要求组中收缩末期为重建时相的比例明显升高。结论:相对时间分辨率是冠状动脉CTA的一项关键要求,ER低于标准则不宜进行检查。

Objective： To evaluate the effect of relative temporal resolution on image quality in clinical 64- MSCT coronary angiography and establish the criteria of heart rate selection in coronary CTA. Methods： 496 patients who underwent 64-MSCT coronary angiography with approximately normal cardiac function were included in the study. Images from 30% to 80% of cardiac cycle were generated with single sector reconstruction. The images at the vertical portion of the right coronary arteries in single cardiac cycle were used for selection of the cardiac phase with minimal motion artifact, and the heart rate at the cardiac cycle was recorded for calculation of relative temporal resolution. Then the images of the middle portion of right coronary arteries at the best cardiac phase were used for scoring of motion artifacts. We used a term named effective reliability （ER） to describe effective temporal resolution. The relationship between ER and image quality was analyzed to carry out the threshold of ER for different image quality requirements. Groups with acceptable ER and unacceptable ER were compared for the cardiac phase of reconstruction for optimal image quality. Results： Among the 496 patients, heart rates ranged from 43 bpm to 103 bpm. Using the score of 3 as the acceptable image quality, an ER of Sl was considered as the lower limit for successful examination. Using score 4 as the acceptable image quality, an ER of 84 was considered the lower limit. There is significant difference in phase selection between the groups with acceptable ER and unacceptable ER, with more reconstruction in end systole in the group with unacceptable ER. Conclusion： Relative temporal resolution is a critical point for coronary CT. A patient with an ER under the threshold is not a proper candidate for coronary CT imaging.