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.
