Year: 2016
Type: article
Abstract: ICTR-PHE 2016 S7two scenarios defined by different tissue parameter values (α/β)x representing high and low radio-sensitivity.We systematically compared RBE predictions as a function of (α/β)x and proton linear energy transfer (LET) values in a spread-out Bragg peak (SOBP) in water and analysed results on patient-CT anatomy for cranial irradiation in terms of absorbed dose-to-water, dose-averaged LET (LETD), RBEweighted dose-to-water and biological range shift distributions.Results: Different levels of agreement depending on (α/β)x and LET values were found in the systematic comparison of RBE predictions.The SOBP study emphasizes a variation of LETD and RBE not only as a function of depth but also of lateral distance from the central beam axis.Applying the different models to cranial treatment plans we observe consistent discrepancies from the values obtained for a constant RBE of 1.1 when using the variable RBE scheme in tissues with low (α/β)x, regardless of the model.An example is reported in figure 1. Biological range shifts of (0.6-2.4) mm (high (α/β)x) and (3.0-5.4)mm (low (α/β)x) were found in the fall-off analysis of individual profiles of RBE-weighted fraction dose along the beam penetration depth.Conclusions: Although more experimental evidence is required to validate the accuracy of the investigated models, their consistent trend suggests that their main RBE dependencies should be included in treatment planning systems.Evaluation of the impact of a variable RBE scheme on the plan optimized using a constant RBE would thus be enabled, constituting a first step towards a more robust choice of biological dose delivery in proton therapy.
Source: Radiotherapy and Oncology
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,770
OpenAlex ID: W2292019254