螺旋CT扫描的深部剂量研究

The Study on Depth Dose in Spiral CT Examnation.

目的 研究多层螺旋CT扫描的深部剂量分布 ,并导出剂量随受照深度变化的拟合方程。方法 用热释光剂量计和改进后的CT标准剂量监测模体 ,在MX -80 0 0多层CT机上 ,按 4层常规扫描参数 ,分别在模体径向方向的中心轴 0 ,3 7 5 ,75 ,112 5和 15 0mm处测量了辐射的平均剂量。结果 CT扫描的辐射剂量随入射深度的增加而减小 ,呈指数衰减规律。结论 若已知扫描器官对应的体表剂量A ,则可根据剂量随深度变化的拟合方程 ,求得该器官的吸收剂量D =Ae- 0 0 0 4 4x。

Objective To study the depth dose distribution and to summarize the regression equation. Methods A MX-8000CT scanner is used with TLDs and modified CT standard dosimetry phantom. Under 4-slice spiral CT scan with routine clinical parameters the measurements of average radiation dose are performed at radii of Omm, 37.5mm, 75mm, 112.5mm and 150mm from the center of the phantom. Results The radiation dose is in exponential attenuation with the increasing of the depth. Conclusion Knowing the surface dose A during CT examination the radiation dose to organ in vivo could be calculated using the regression equation D=Ae -0.0044x.