心率不稳定时3种不同重建算法对影像质量的影响:MSCT动态心脏体模研究

目的研究心率不稳定时,多层螺旋CT3种不同重建算法对影像质量的影响及时间分辨力,明确快速心率条件下最佳成像方式。方法对象为一个新型动态心脏体模。调节体模,模拟心率60bpm、85bpm和105bpm,各种基础心率都有0、2.5、5、10、15次几种波动。采用GE公司LightSpeed16层螺旋CT机进行扫描。基础心率为60bpm和105bpm时电流300mA,X线管旋转时间为0.5s/周;基础心率85bpm时电流250mA,X线管旋转时间为0.6s/周。将原始数据分别以Snapshot Segment、SnapshotBurst、Snapshot Burst Plus3种方式重建成层厚0.625mm,间隔0.625mm影像,标准重建算法(std),舒张期(ED)采用R-R间期的90%,在Adw4.2工作站进行VR及能显示狭窄层面的MPR重组。依影像质量优劣制定5分评分标准,由3位放射医师采用盲法对影像质量进行评分,取3位医师对重建影像的平均评分进行比较。计算不同基础心率不同重建模式下的时间分辨力。结果(1)在每种基础心率下,随波动幅度增加,3种不同算法所得影像质量都下降。(2)心率60bpm时,同一波动幅度下3种不同算法在对影像质量影响差别不大,仅波动2.5次时Snapshot Segment略差,而波动10、15次时Snapshot Segment略好。对应的时间分辨力分别为250ms、245ms、245ms。(3)心率85bpm及心率波动为0、2.5、5时Snapshot Burst Plus所得影像质量最高,而心率波动为10、15时以Snapshot Burst所得影像质量最高。相应的时间分辨力分别为为300ms、214ms、80ms。(4)心率105bpm时,心率波动为0、2.5、5、10时Snapshot Burst Plus所得影像质量最高,而心率波动为15时以Snapshot Burst所得影像质量最高。相应的时间分辨力分别为250ms、191ms、84ms。结论在每种基础心率状态下,3种不同重建算法所得最好影像质量皆随心率波动幅度的加大而下降。

The Effect of Heart Rate Fluctuation and Different Algorithm on Image Quality with Multislice Spiral CT: A Dynamic Cardiac Phantom Study

Objective To evaluate the effcct of heart rate (HR) fluctuation and different algorithm on image quality with multislice spiral CT. To confirm the best combination between different HR fluctuation and algorithm. Methods The phantom could simulate the left ventricle and coronary arteries in different condition. Adjust HR in 60, 85, 105 bpm, each conditon had shift of 0, 2.5, 5, 10, 15. The scanner was a GE Lightspeed 16-slice spiral CT, when the HR was 60 bpm and 105 bpm, the mA was 300 mA,the rotation time was 0.5 s/r,while when the HR was 85 bpm, the mA was 250 mA,the rotation time was 0.6 s/r. All the scanning data was reconstructed with three different algorithm that was Snapshot Segment,Snapshot Burst and Snapshot Burst Plus respectively. The thickness and interval were 0.625 mm, then VR and MPR images were reformatted on Adw4.2 workstation. A five grade standard was made based on the image quality. The image quality was evaluated blindly by three doctors and the mean score was compared. The time resolution was also calculated in the circumstance of 60, 85, 105 bpm.Results (1)At each base HR, with the range of fluctuation increased, the image quality of three different algorithm decreased. (2)When HR was 60bpm, the image quality had no obvious different with three algorithm in the same range of fluctuation, only at shift of 2.5, Snapshot segment was slight bad, otherwise at shift of 10,15,Snapshot Segment was slightly good. The corresponding time resolution was 250,245 and 245 ms respectively. (3)When HR was 85bpm and the range of fluctuation was 0, 2.5, 5, the image quality of Snapshot Burst Plus was the best, otherwise when the range of fluctuation was 10 and 15, the image quality of Snapshot Burst was the best. The Corresponding time resolution was 300, 214 and 80ms. (4)When HR was 105bpm and the fluctuation was 0,2.5,5 and 10, the image quality of Snapshot Burst Plus was the best, otherwise when the fluctuation was 15, the image quality of Snapshot Burst was the best. The corresponding time resolution was 250 , 191 and 84 msrespectively.Conclusion At each base HR, the image quality ofthree different algorithm is decreased with the increase of the range of fluctuation.