医用X射线CT辐射剂量影响因素研究

目的分析不同管电压、管电流、模体直径、模体内深度、螺距、准直宽度、照射野、算法及管电流调制技术等因素对多层CT辐射剂量的影响。方法用CT笔形电离室、头部和体部剂量模体及国人仿真人体模型．在CT机上测量在不同管电压、管电流、模体直径、模体内深度、螺距、准直宽度、照射野、算法及管电流调制技术条件下的CT剂量学表征量。结果当其它参数一定时．管电压与CT剂量成正比；管电流与CT剂量成线性正相关；模体直径与CT剂量成反比；CT剂量随模体内径向深度的增加而减少；螺距与剂量成反比，螺距的增加使超成像范围的剂量增加；准直宽度与剂量成反比；照射野和算法对CT剂量没有影响；采用管电流调制技术可降低CT剂量。结论降低管电压、降低管电流、增加螺距、限制分段扫描、增加准直宽度、降低体形瘦小受检者的扫描条件及采用管电流调制技术可使CT剂量降低。

An evaluation on influence factors of radiation dose for the medical X-ray computed tomography

Objective To evaluate those factors which affect on to the radiation dose of multi-slice CT, such as voltage and current of tube, diameter of phantom, depth of inside phantom, pitch, collimation, field of view, algorithm and tube current modulation technology and so on. Methods A pencil-llke ion chamber, head and body dose phantom, and Chinese anthropomorphic phantom were used to measure the characteristic quantum of CT dosimetry when different voltage and current of tube, diameter of phantom, depth of inside phantom, pitch, collimation, field of view, algorithm and tube current modulation technology were adopted. Results When all other parameters kept unchanged, the tube voltage was direct proportional to CTDI （CT dose index）, the tube current was positive linear correlation to CTDI, the diameter of phantom was inverse proportional to CTDI, radiation dose of CT was decreasing while measuring depth increased of inside phantom, pitch was inverse proportional to accumulated dose, overexposure from spiral scanning out of topogram range led to the increasing of radiation dose, collimation was inverse proportional to CTDI, CTDI was not affected by field of view and algorithm, and radiation dose of CT was decreased by using tube current modulation technology. Conclusion Radiation dose of CT can be decreased by reducing voltage and current of tube, increasing pitch,limiting the block number of helical scanning during a single CT examination, increasing width of collimation, decreasing scan parameters of slim patients rationally and adopting tube current modulation technology.