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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。
Objective: To investigate the influential factors of image quality in Digital Subtraction CT Angiography (DSCTA). Methods: The skull base vascular model and 16-slice CT (Brightspeed elite) scan were performed: 1) The same parameters of axial helix and non-helix were repeated 10 times; (2) The same parameters of both groups were placed in the same sequence, Different time (2.3s, 3.5s, 4.1s, 4.7s, 5.9s; 4s, 5s, 6s, 7s, 8s) and different collection layers (32,41,48,51,55; 60,64,72, 77,80), each repeated 1 scan; (3) simulated injection according to (2) parameter scanning, collecting 80 layers, the exposure interval of 2.4s, repeated 5 scans. Results: The non-helical axis scan was repeated 10 times, the success rate of subtraction was 100%, and the success rate of helical axis scan was 10%. The same sequence of same scan, the repeat interval of tube was an integral multiple of 0.6 When the success rate of subtraction 100%, the tube repeat exposure interval is not an integer multiple of 0.6 when the reduction is not successful. Different acquisition layers subtraction success rate of 85%, unsuccessful scan complete subtraction subtraction. The simulated tube repeat exposure time was 9s, the success rate of 5 times subtraction was 100%, and a clear subtracted “blood vessel” image was obtained. Conclusion: The start position of the tube exposure is an important factor affecting the quality of the DSCTA image. Controlling the repeat exposure time of the tube to be an integral multiple of the tube rotation speed can ensure the same starting position of the tube exposure. The width of the detector does not affect the DSCTA Image Quality.