Metrological and treatment planning improvements on external beam radiotherapy. Detector size effect and dose calculation in low‐density media (in Spanish)

Abstract

The objective of this thesis is the improvement of the measurement and calculation accuracy for radiation therapy fields. Basically, it deals with two questions: the detector size effect and the heterogeneity dose calculation. The author analyzes both the metrological and computational effects and its clinical implications by simulation of the radiotherapy treatments in a treatment planning system. The detector size effect leads up to smoothing of the radiation profile increasing the penumbra (20%–80%) and beam fringe (50%–90%) values with the consequent clinical effect of over‐irradiation of the organs at risk close to the planning target volume (PTV). In this thesis this problem is analyzed finding mathematical solutions based on profile deconvolution or the use of radiation detectors of adequate size. On the other side, the author analyzes the dose computation on heterogeneous media by the superposition algorithms versus classical algorithms. The derived conclusion from this thesis is that in locations like lung and breast, the classical algorithms lead to a significant underdosage of the PTV with an important decrease of tumor control probability (TCP). On this basis, the author does not recommend the clinical use of these algorithms in the mentioned tumor locations.