Automated calculation of optimum dose distribution and irradiation condition for intracavitary treatment of uterine cervix carcinoma

Widely employed dose calculation system of the intracavitary radiotherapy for carcinoma of the uterine cervix is done according to X-ray photographs which are taken after the insertion of dummy sources. Thereafter, the radiation dose can be decided on symmetrical standard isodose curve obtained from the Manchester system, in general. In this research, the standard isodose curve of the Manchester system is simulated by applying the point source arrangement in the remote afterloader, and then, the simulated isodose curves are fitted by polynominal of higher orders using polar coordinates. The isodose curve for each patient is calculated using the geometrical arrangement of tandem and ovoids and interpolation of the simulated isodose curve. We called it a semi-standard isodose curve. Several points defined as selected ones are extracted on the semi-standard isodose curve. Moreover, the positions of the selected points are modified to fit to actual source arrangement. Optimum irradiation time is calculated to satisfy predefined dose of the selected points for therapy using quadratic programming. If predefied dose of the isodose curve and source coordinates of X-ray photograph are put in computer, it takes less than 30 seconds to obtain the following: optimum irradiation time and positions of sources, length of pull back from top of tandem source and positions and calculated dose of selected points. Our computer-aided calculation system is useful in clinical practice for remotely controlled afterloading therapy for carcinoma of the uterine cervix. (author)