Dosimetry in linear accelerators of medical application

In daily practice of radiotherapy it is necessary to supply patients high radiation doses: on the exactness of suministration of such doses depends the success or the failure of treatment. For this reason it is necessary to improve in every moment the certainty of measure the dose supplied by means of a high energy radiation beam. This work shows the methods used at present to measure the doses by means of gas ionization in an electron linear accelerator of high energy of medical application. The method starts with Bragg Gray theory, using it to obtain the dose by means of corrections of radiation beam when it crosses the measurement cavities. In the National Oncology Institute (Instituto Nacional de Cancerologia) the method used at present for dose measurement is the IAEA protocol issued in 1987 which is follow in this work because one of its more important contributions is direct relationship of a secondary laboratory of calibration with Medical Physics departments. (Author)