抄録
Spatial coordinates of interest points for intracavitary radiotherapy is usually decided on the basis of radiographic projections obtained in two different directions. Errors or inconsistencies in the image coordinates read from the radiographs happen for such reasons as patient's movement between the two images, uncertainties in magnification and the mutual angle between the two radiographic projections. A position calculated by a theoretically correct geometrical formula sometimes has a greater error than one obtained by the approximation method with constant magnification because of a large propagation of the errors. This report indicates useful geometrical solutions and least squares methods for an optimun determination of spatial coordinates.
