Optimising The Production Process Of Wood’S Alloy End-Frames For Electron Field Shaping In Radiotherapy

Abstract

Skin cancer is commonly treated by means of electron radiation generated by a linear electron accelerator (linac). The radiation applied must be limited or shaped to the size of the cancer-affected area on the patient. This is achieved through applicators that attach to the linac unit, while more precise field shaping is made possible through end-frames that fit into the front end of the applicators. The end-frames are machined out of high-density metal such as lead or, as in recent years, cast in Wood’s alloy. Commercial jigs used to cast the Wood’s alloy present various shortcomings in terms of dimensional accuracy of the end-frames, density of the castings and high cost of the jigs. The aim of this study was to develop a Wood’s alloy casting unit that can be made available to local oncology units to produce end-frames that are superior to what can be achieved through commercial jigs. The development and manufacturing of the new casting equipment is described as well as experiments that were performed to evaluate the equipment by comparing end-frames produced to those that were cast in the commercial jig. Results of the experiments show that end-frames cast in the newly developed casting equipment are dimensionally accurate, have consistent high density and can be produced in a short timeframe.