Abstract:
Radiation oncology is based on the use of ionizing radiation sources which deliver a prescribed dose to the identified tumour. The source may irradiate the tumour from outside by external radiation or, the tumour is exposed to the radiation emitted by a radionuclide, which is incorporated in the cancerous tissue. In both cases, the personnel engaged in the treatment may be exposed to some radiation doses which have to be kept as low as possible taking into account all possible circumstances. In addition to receiving a planned relatively high dose to the tumour, the patient may also be exposed to some doses affected healthy tissues which are located close to the tumour. This exposure, although comparatively much lower that the dose to the tumour, has also to be reduced to a very minimum possible. The requirement follows a very basic principle of radiation protection aimed at the reduction of undesirable exposure as much as possible since any dose, whatever low, can be harmful due to stochastic radiation effects which lead to the development of cancer with the probability proportional to the radiation exposure.