Dosimetry from organ to cellular dimensions

While the conventional Medical Internal Radiation Dose (MIRD) approach is u seful for estimating approximate organ absorbed doses in diagnostic applica tions of isotopes, this strategy is suited neither to the exacting requirem ents of targeted radionuclide therapy nor to radiopharmaceuticals with a no n-uniform activity distribution. For the individual treatment planning of p atients treated with common radionuclides emitting high energy betas, the i ndividual activity distribution has to be obtained from CT-SPECT images and the doses to the target organs and critical tissues have to be calculated by point-kernel methods. Due to the stochastic nature, alpha-radioimmunothe rapy (alpha-RIT) requires microdosimetric calculations with Monte Carlo on a realistic model of the source and target tissue at the micrometer level. For a prediction of the biological effects of intracellular labelling with Auger electron emitters an accurate subcellular modelling including the DNA structure at the nanometre level with knowledge of the target for the cons idered biological effect is necessary. (C) 2001 Elsevier Science Ltd. All r ights reserved.