Estudo de parâmetros dosimétricos e dosimetria in vivo em radioterapia

Abstract

ALVA SANCHEZ, M. S. Study of dosimetric parameters and in vivo dosimetry in Radiotherapy. [Dissertation]. Ribeirao Preto: Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo; 2007. 60 p. The expected outcomes in Radiotherapy require a strict quality control program to be performed in order to evaluate the doses delivered to patients. Accordingly to the International Commission on Radiation Units and Measurements (ICRU) the possible discrepancies between prescribed and delivered doses to patients must be in a range of -5% and +7%. Treatments of total body irradiation (TBI) use large source-surface distances and broad radiation fields, showing high complexity when compared to conventional procedures and do not present a well-established protocol for the calculation of the absorbed dose. On the other hand, considering, the severe collateral effects associated to this treatment, TBI requires a rigorous control of the doses administrated to the patient and a program of verification of the treatment through in vivo dosimetry is paramount. This work presents a study of dosimetric parameters for both conventional and total body irradiation treatments as part of a quality control program in Radiotherapy. The dosimetric parameters had been determined using termoluminescente dosimetry, ionization chamber, and semiconductor dosimeters. Possible corrections for the use of the conventional conditions-obtained parameters in total body irradiation were evaluated. An in vivo dosimetry methodology had been also studied to be applied to TBI treatments. The obtained results leads to the conclusions that TBI dosimetric parameters must be obtained under proper irradiation conditions and should not be adapted from conventional conditions and that entrance dosimetry is an adequate technique to evaluate delivered doses in TBI.