Dosimetric analysis of uncertainties derived from movement and density variations evaluated with Image-Guided Radiotherapy in lung Stereotaxic Radiotherapy
DOI:
https://doi.org/10.37004/sefm/2020.21.2.003Keywords:
SBRT, IGRT, Heterogeneity, Dose verificationAbstract
Objective: To carry out an estimation in position and density variations by analysing volumes determined in cone beam images obtained during stereotactic radiotherapy lung treatments and its impact on delivered dose to tumour.
Materials and methods: Prescription dose for PTV (Planning Target Volume) and dose value obtained in tumour have been calculated, taking into account forced density override of PTV without forcing. Difference between Monte Carlo and Collapsed Cone algorithms has been studied. The treatment has been re-calculated on volumes generated by cone beam images, considering same density as tumour. Theoretical dosimetry has been carried out on cylinders with different shifts from isocenter in order to evaluate its impact on received dose comparing to other clinical cases
Results: Prescription dose for PTV forcing density override leads to greater dose calculated on tumour of 10.6% and 8.2% without forcing. Volumes delineated on cone beam images receive approximately the same dose as the tumour determined in planning, dose differences being blamed to position uncertainty.
Conclusions: Dose calculated on volumes determined on cone beam images obtained during treatment could lead to prescription dose evaluation.
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