数字减影CTA图像质量影响因素探讨

目的:探讨数字减影CTA(Digital Subtraction CT Angiography,DSCTA)图像质量的影响因素.方法:用颅底骨血管模型,16层螺旋cT(Brightspeed elite)扫描:1)轴位螺旋和非螺旋同一参数重复10次扫描;(2)两组同样的参数放在同一序列内,曝光间隔时间不同(2.3s,3.5s,4.1s,4.7s,5.9s;4s,5s,6s,7s,8s)和采集层数不同(32,41,48,51,55;60,64,72,77,80),各重复1次扫描;(3)模拟注药后按(2)的参数扫描,采集80层,曝光间隔时间为2.4s,重复5次扫描.结果:非螺旋轴扫重复10次,减影成功率为100%,螺旋轴扫重复10次减影成功率为20%;同一序列相同两组扫描,球管重复曝光间隔时间为0.6的整数倍时减影成功率为100%,球管重复曝光间隔时间不为0.6的整数倍时减影均不成功.不同采集层数减影成功率为85%,不成功扫描重复后完全减影.模拟注药后球管重复曝光间隔时间为9s,5次减影成功率为100%,得到清晰的减影"血管"图像.结论:球管曝光起始位置是影响DSCTA图像质量的重要因素,控制球管重复曝光间隔时间为球管转速的整数倍可确保球管曝光起始位置相同;探测器的使用宽度不影响DSCTA的图像质量.

Digital subtraction CT Angiography( DSCTA ): influencing factors for image quality

Objective:To explore the possible influencing factors for image quality of digital subtraction CT angiography(DSCTA).Methods:Vascular model of the skull base was observed using 16-slice spiral CT(Brightspeed elite).(1)Each parameter was scanned for 10 times at both spiral and non-spiral axial view.(2)Two uniform parameters were compared in the same sequence at different exposure intervals(2.3s,3.5s,4.1s,4.7s,5.9s;4s,5s,6s,7s,8s)and different slices(32,41,48,51,55;60,64,72,77, 80)and scanned twice.(3)After injection simulation,the vascular model was scanned for 5 times using the same parameters as above and 80 slices were collected at an exposure interval of 2.4s. Results:The subtraction was 100% successful by non-spiral scanning, while 20% by spiral scanning in 10 times. Within the same sequence, the subtraction was successful only if the tube repetition exposure interval time was integrally divided by 0.6s. The subtraction rate was 85%, in different slices used. The tube exposure interval was 9s. The clear vascular image was obtained after scanning for 5 time. Conclusion Home position of tube is critical to the DSCTA image quality and can be maintained only If the tube repetition exposure interval time integrally divided by the rotation speed. Width of detector has no influence on the DSCTA image quality.