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RBE Algorithm Parameter Optimization and Statistical Analysis

P Ambrozewicz*, C Keppel ,


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Optimization of parameters that are needed in modeling Relative Biological Effectiveness (RBE) in proton therapy treatment planning.

Methods: Experimental data were collected from existing publications and a newly created relational database was populated with these data. The data were refitted and new parameters were extracted and compared withthe published ones.

Results: While proton therapy is becoming increasingly widespread and efficient, therepersists uncertainty regarding the biological effects of proton irradiation,typically expressed in terms of relative biological effectiveness (RBE). A markedvariation in the RBE for tumor cell killing along the depth dose profile of protonbeams has been shown, while the standard is to apply a uniform factor of 1.1 intreatment planning.The development and implementation of a data-driven algorithm toaccount for RBE at the treatment planning level could alleviate this concern. Tothis end, an ongoing project has obtained an expanded RBE data set to implement RBEweighting into the Varian Eclipse treatment planning software product. Achievingthis goal has required the development of an RBE model and an application algorithm.We anticipate the introduction of biological weighting factors that are specific forthe linear energy transfer, LET, of protons at a given tissue depth to furtherimprove the therapeutic ratio of proton therapy. However, the adopted definition ofRBE turns this into a multi-dimensional problem, which can only be solved byrigorous data analysis. For this purpose a relational database has been developed tocontain and compare the results of available experimental measurements. This turnedout to be a surprisingly challenging undertaking as the available data suffers fromoften insufficient quantity reporting and statistical analysis.

Conclusion: A summary and status of this work will be presented.

Funding Support, Disclosures, and Conflict of Interest: Varian Medical Systems


Protons, RBE, Statistical Analysis


TH- External Beam- Particle therapy: Proton therapy - Development (new technology and techniques)

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