Evaluation of Radiobiological Effects in Intensity Modulated Proton Therapy : New Strategies for Inverse Treatment Planning

Currently, treatment planning for intensity modulated proton therapy (IMPT) usually disregards variations of the relative biological effectiveness (RBE). To investigate the potential clinical relevance of a variable RBE for beam scanning techniques, new strategies for the evaluation of radiobiological effects and for the incorporation of the RBE into the inverse planning process are presented. These strategies are based on a fast algorithm for three-dimensional calculations of the dose averaged linear energy transfer (LET) as a measure of the local radiation quality, and on a simple phenomenological approach for the RBE as a function of dose, LET and tissue type. It was found that the biological effect depended strongly on the type of scanning technique used, mainly due to differences in the LET distributions. New objective functions that account for LET and RBE were integrated into an inverse planning software, which now allows simultaneous multi-field optimization of the biological effect in a reasonable time. With these methods, unfavourable RBE effects can be identified and compensated for by direct optimization of the product of RBE and dose, which is demonstrated for several clinical examples. The proposed strategies are therefore valuable tools to evaluate and improve the quality of treatment plans in IMPT.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Heidelberg

Year

2004

Author dc:creator

• Wilkens, Jan Jakob

Contributors dc:contributor

• Oelfke, Uwe

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/4673

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:4673