[Questions of accuracy when using "not therapy-specific" computer systems for irradiation planning (author's transl)].

The conditions were examined under which little and medium computer systems not having been primarily developed for radiotherapy can be used in order to make sufficiently precise calculations of dose distributions. The adapted accuracy of the principal factors influencing the dose distribution renders possible a time-saving calculation of several dose distributions and a final calculation. By comparison with a reference calculation made as accurately as possible, the isodose curve shows only little deviations. The following factors were examined in order to find out an eventual influence exerted upon an isodose displacement: number of scan points in the cross-section, correction of the oblique ray incidence, inhomogeneities, dissociations of the rotation field. To our opinion, the isodose displacements found for a dose calculation with adapted accuracy are acceptable when related to influencing factors depending on the individual patients.