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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。
Objective To study the effects of three different reconstruction algorithms of multi-slice spiral CT on the image quality and time resolution when the heart rate is unstable, and to find out the best imaging mode under the condition of fast heart rate. Methods The object is a new type of dynamic heart phantom. Regulate phantom, simulate heart rate 60bpm, 85bpm and 105bpm, various basic heart rate has 0,2.5,5,10,15 times several fluctuations. Scan with GE LightSpeed 16-slice CT scanner. The basal heart rate was 60bpm and the current was 105mA at 105bpm. The rotation time of the X-ray tube was 0.5s / week. The current of the basal heart rate was 85mA at 85bpm and the rotation time of the X-ray tube was 0.6s / week. The original data were reconstructed into 0.625mm slice and 0.625mm slice respectively by the methods of Snapshot Segment, SnapshotBurst and Snapshot Burst Plus. The standard reconstruction algorithm (std) was used. The diastolic phase (ED) was 90% of the RR interval. 2 workstation for VR and can display a narrow level of MPR reorganization. According to the quality of the image to develop a score of 5 points, three radiologists use the blind method to score the image quality, take three doctors to compare the average score of the reconstructed image. Calculate the time resolution of different basal heart rate in different reconstruction modes. Results (1) At each basic heart rate, the image quality of the three different algorithms decreased with the increase of fluctuation amplitude. (2) When the heart rate is 60bpm, the three different algorithms with the same fluctuation have little difference in the image quality. The Snapshot Segment is slightly worse only with fluctuations of 2.5 times, while the Snapshot Segment is slightly better with the fluctuations of 10 and 15 times. The corresponding time resolution is 250ms, 245ms, 245ms respectively. (3) Snapshot Burst Plus achieved the highest image quality with a heart rate of 85bpm and heart rate fluctuations of 0, 2.5, and 5, while Snapshot Burst was the highest quality image with heart rate fluctuations of 10,15. The corresponding time resolution were 300ms, 214ms, 80ms. (4) Snapshot Burst Plus achieved the highest image quality at heart rate of 105bpm with heart rate fluctuations of 0, 2.5, 5, and 10, while Snapshot Burst achieved the highest image quality at a heart rate of 15. The corresponding time resolution of 250ms, 191ms, 84ms. Conclusions The best image quality obtained with the three different reconstruction algorithms at each baseline heart rate declines with increasing heart rate variability.