We present a fast method to create interstitial oxygen concentration maps from resistivity calibrated photoluminescence images prior to and after a heat treatment at 450 degrees C. The method utilizes the influence of thermal donors on the effective doping concentration of a sample. Although the determination of thermal donor concentrations from conductivity measurements is customary in literature, we found that implementation of a mobility model is necessary to determine accurate concentrations of thermal donors. Therefore an iterative correction algorithm is presented, which allows precise determination of thermal donor concentrations from resistivity measurements. The determination of interstitial oxygen concentrations from thermal donor concentrations is based on an updated parameterization based on a model of Wada et al. (Phys. Rev. B: Condens. Matter 30 (1984) 5884-5895) that is also presented in this paper. The method is demonstrated on a 1.3 Omega cm p-type Czochralski grown silicon sample with an interstitial oxygen concentration in the range of 7.5 x 10(17) cm(-3) and yields good agreement with FTIR measurements. (C) 2014 Elsevier B.V. All rights reserved.