Purpose/Objective(s): To show feasibility of an analytical conversion strategy of dose to single and double strand break damage maps. To facilitate and quantify dose painting levels based on physical parameters like dose deposited, electron spectra, and absolute estimates of oxygenation levels. Materials/Methods: An analytical expression is used that parameterizes the impact of radiation as the number of induced single (SSB) and double (DSB) DNA strand breaks as a function of electron energy (E) and the partial oxygen pressure (pO2). To test this, dose deposition volumes were registered to CT and PET (F-HX4) images containing information on oxygenation levels. The PET images were corrected for mass density to eliminate activity variations due to physical density rather than biochemical processes. Knowledge of the spectrum of the depositing electrons calculated using Monte Carlo simulations was used to convert dose to two damage maps of respectively, single and double strand breaks. To obtain a relevant comparison the same calculation is repeated using a single level of pO2 Z 30%. Dividing both distributions yielded two values per pixel (RBEs and RBEd) denoting the relative damage level commensurate with each damage type. The partial oxygen pressure was determined from the PET scan using a linear model, where a region of known normal oxygenation is used to determine the uptake in normoxic environments, which is used as a calibration set. The level of normoxicity is varied to determine the robustness of this approach to the accurate knowledge of pO2. Results: In all cases it was found that RBEs was not equal to RBEd, implying that, to correct for hypoxic conditions, the use of dose escalation is not possible if the goal is to get the exact same induced damage. The RBE factors’ dependence on the choice of the normoxic level in the PETimage was observed, but the correlation was weak. A variation of 50% introduced a RBEd of 2.5% and a RBEs of 0.8%. The levels needed to obtain the same DSB and SSB damage were respectively 2.2% and 1% dose increase. Conclusions: Using a fast biological conversion algorithm it is possible to provide quantifications of DNA damage in a clinical environment. The use of PET imaging to determine, absolute hypoxia measurements or uptake of other dose-enhancing agents will become vital in using this technology. Author Disclosure: F. Van Den Heuvel: None. D. De Ruysscher: None. W. Van Elmpt: None. S. Nuyts: None.