Dosimetric verification of breathing adapted radiotherapy using polymer gel

摘要

In radiation therapy patient movement caused by respiration can be a major challenge to the ambition to deliver a high absorbed dose to the target volume while minimizing the dose to normal tissues. Large respiratory motion requires increased margins, which implies an increased risk of morbidity from late toxicity. It is therefore important to take respiratory motion into account when treating targets in the thorax region. Studies show that breathing adapted radiotherapy (BART) of breast and lung cancers reduces the dose to organ at risks, without compromising target coverage [1,5]. Respiratory gating is a BART method that allows radiation beam-on only during a certain pre-specified phase of the respiratory cycle. Depending on the length of the duty cycle, however, a certain dose smearing of the field edges due to movement during the beam-on time will remain [2]. Other factors, such as for instance accelerator output stability during switching on and off the beam, may also contribute to the uncertainty of the delivered dose [4]. In previous studies, ionization chambers, film and diode arrays have been used for dosimetric verification of gated dose delivery in 1D or 2D [2,3]. However, there is no experimental 3D data on the dosimetric benefit of respiratory gating. The aim of this study was to investigate the feasibility of using a 3D gel dosimeter for dose verification of breathing adapted radiotherapy.