Traceable dosimetry for molecular radiotherapy

The therapeutic effect from molecular radiation therapy (MRT) on tumour tissue and its adverse effect on normal tissue are both determined by the radiation quantity absorbed dose. Recent research indicates that, as a consequence of biological variation across patients, the same activity administered to different individuals may deliver a very wide range of absorbed dose. Within the European Metrology Research Program (EMRP) joint research project - Metrology for molecular radiotherapy -MetroMRT- is addressing the extent to which absorbed dose can be quantified on a customised basis. The MetroMRT project aims to formulate a dosimetry concept for MRT in terms of calibration and verification of dose planning tools, with a measurement chain that is traceable to primary standards with known measurement uncertainties. The project consists of three parts investigating the three key links in the dosimetry chain: activity measurement, quantitative imaging measurement of uptake, and verification of absorbed dose estimates. The third part explores both experimentally and theoretically ways in which the calculated absorbed dose can be verified against measurements using geometrical configurations and radionuclides that are relevant to MRT treatments. It is expected that the outcome from this research will be formulated guidelines on best practice, and dose verification/audit services provided to clinics. The dosimetry techniques that have been investigated and developed by National Metrology Institutes within the project will be discussed and the results of feasibility studies, measurements and Monte Carlo calculations will be presented. (authors)