【摘要】 目的探讨多层螺旋CT的扫描参数螺距的变化对辐射剂量的影响。方法对于LightSpeed16层螺旋CT和Sensation16层和64层螺旋CT,将长杆电离室分别置于16mm剂量体模的5个孔中,选用不同的螺距进行扫描并测量辐射剂量。结果3种机型轴扫和螺旋扫描的CTDIvol分别为:(1)对于lightSpeed16层螺旋CT,在轴扫及螺距分别为0·562、0·938,1·75时,分别等于28·9、51·4、30·8,16·5;(2)对于Sensation16层螺旋CT,在轴扫及螺距分别为0·5,1、1·5时,分别等于41·2、40·3、41·5,43·2;(3)对于Sensation64层螺旋CT,在轴扫及螺距分别为0·5,1·1·5时,分别等于41·2、40·3、41·5,43·2。结论对于LightSpeed16层螺旋CT,随着螺距的增加,辐射剂量降低,为保持恒定的图像质量,必须增大mAs作为补偿;Sensation16层和64层螺旋CT,因采用了mAs自动调整技术,在不同的螺距下辐射剂量相同,图像质量稳定。日常操作中当螺距改变时,应根据不同机型来确定调整管电流的方法。更多还原

【Abstract】 Objective To study the relations of radiation dose and spiral pitch for multi-slice CT system. Methods 16 mm dose phantom with solidose 300/400 pen-style ion chamber inserted into each of five holes in turn was scanned with different spiral pitch by LightSpeed 16-slice CT and Sensation 16-slice and 64-slice CT and radiation dose. Results CTDI_ vol of axial scan and spiral scan for the three types of CT system are: (1)LightSpeed 16-slice CT: 28.9(axial),51.4(pitch 0.562),30.8(pitch 0.938) and 16.5(pitch 1.75);(2)Sensation 16-slice CT: 41.2(axial) and 40.3(pitch 0.5),41.5(pitch 1) and 43.2(pitch 1.5);(3)Sensation 64-slice CT: 41.2(axial) and 40.3(pitch 0.5),41.5(pitch 1),43.2(pitch 1.5). Conclusions For LightSpeed 16-slice CT,the measured radiation dose decreased with the increase of spiral pitch,the image quality could keep constant only if we increase mAs.While for Sensation 16-slice and 64-slice CT system,the measured radiation dose was identical for different pitch,and the image quality was identical because of the use of mAs auto control technique The mAs should be adjusted in different way according to the type of CT system when the pitch is changed in daily operation.更多还原