DETERMINATION OF SOURCE-POSITION TIMES IN INTRACAVITARY RADIOTHERAPY.
Prior to treatment using a single source remote afterloading system the source-position times must be determined. Initially the ideal but theoretical source-position times are calculated using a system of linear equations. In most cases however, one or more of the solutions are negative. Assuming that the best physical answer may be obtained if these negative values are held at zero, the matrices are reduced using linear regression techniques. The reduced set of equations is then used to solve for the new times. This procedure is repeated until no further negative solutions are obtained. Using these final values, dose distributions are plotted, and are found to correspond to within 5% of those initially requested.