Ontwikkeling van 'n rekenaar numeries-beheerde radiaal freesmasjien vir gebruik in radioterapie

Abstract

Deeply situated cancer is commonly treated by means of irradiation with high energy X -rays. Problems do arise however when a tumor is irradiated below an uneven skin surface since the amount of tissue between the skin and tumor varies across the radiation field. As a result of this, the transferred radiation dose will also vary through the volume of the tumor. This effect results in inaccurate treatment that necessitate attention. An effective solution to the problem will be to fabricate a compensating filter according to the uneven treatment area on the patient. With such a compensator in the treatment field during irradiation, the effect of variation in the amount of tissue between the skin and tumor will be cancelled to ensure even dose distribution. The effectiveness of existing techniques to fabricate compensators are insufficient in some respects. This study discusses the development of an affordable computer numerical control (CNC) milling machine that is used in a revised technique to fabricate compensators. Contour data of the uneven treatment area on the patient is obtained by means of computer tomography. This data is processed by a treatment planning computer to enable the CNC milling machine to cut a negative of the compensator from a polystyrene block. The machined cavity is filled with a compensating medium with the correct density to complete a compensator. Testing of compensators that were fabricated by this means of compensator fabrication shows effective compensation for uneven treatment areas under simulated treatment conditions.