Fabrication and dosimetry characteristics of intracavitary cones for radiotherapy

A high energy linear accelerator (CLINAC) has been designed exclusively of electron cones for intracavitary radiotherapy. We have designed the intracavitary cones which were made of stainless-steel and have scratched the inside of the cone to generate electron scatter. They are designed to be attached easily to the linac collimator. Dosimetry measurements were made to commission the CLINAC for 6-20 MeV electrons using the intracavitary cones. Two types of intracavitary cones are used. One is the straight end cone with circular opening on the distal end, and the other is 30° beveled end cone with elliptical opening on the distal end. Each type of intracavitary cone ranged in diameter from 2.5 to 3.5 cm and required a separate set of lower trimmer annulias cone diameter. Dosimetric measurements were made to allow the calculation of the monitor setting for delivering a prescribed dose at any depth for any irradiation condition. The characteristics of the isodose data that were analyzed for clinical use included the depth to the 90 percent dose and the geometric coverage of the treatment volume