DOSE CALCULATION IN STATIC OR DYNAMIC OFF-AXIS FIELDS

X-ray fields that are shifted away from the conventional central axis exhibit alterations in output, beam profile, and beam energy. An exten sion of a conventional dose calculation algorithm to correct for these perturbations is presented. This algorithm employs the product of thr ee functions describing the dose at the center of the field at d(max) the relative off-center dose at d(max) and the relative dose at depth along a fanline passing through the point of interest. The nature of t he problem is characterized, a basic data set necessary to support the algorithm is described and an abridged set of data that may assist in the development of an independent collimator dose calculation capabil ity is presented. The appropriateness of this technique for both conve ntional and dynamically collimated fields is illustrated.