螺旋CT定位计算公式的推导与讨论

Reasoning and discussion of spiral CT localization formula

利用螺旋CT定位的几何学原理,推导出床坐标与图层坐标间的函数关系,即当机架角度为0°时,床坐标与图层坐标之间的函数关系式为Twm=S190+M;否则,为Twm=S190/Cosθ+M,结合CT定位实际操作,完成CT定位的计算公式:Twm=S190/Cosθ+M。最后,讨论了计算公式的物理含义和简化条件。

Using geometry principle of the spiral CT localization , functional relation was deduced between the bed coordinates and the diagram layers coordinates, i.e.when gantry angle is zero degree, the function relation type is Twm= S190/Cosθ ＋ M; Otherwise, it is Twin= S190/Cosθ ＋M. Combined with the actual operation of CT localization, the formula of the CT localization is：Twm=S190/Cosθ＋M. Finally, the physical meaning and the simplified condition of the formula were discussed.