Theoretical modeling of yields for proton-induced reactions on natural and enriched molybdenum targets
Recent acute shortage of medical radioisotopes prompted investigations into alternative methods of production and the use of a cyclotron and 100Mo(p,2n)99mTc reaction has been considered. In this context, the production yields of 99mTc and various other radioactive and stable isotopes which will be created in the process have to be investigated, as these may affect the diagnostic outcome and radiation dosimetry in human studies. Reaction conditions (beam and target characteristics, and irradiation and cooling times) need to be optimized in order to maximize the amount of 99mTc and minimize impurities. Although ultimately careful experimental verification of these conditions must be performed, theoretical calculations can provide the initial guidance allowing for extensive investigations at little cost. We report the results of theoretically determined reaction yields for 99mTc and other radioactive isotopes created when natural and enriched molybdenum targets are irradiated by protons. The cross-section calculations were performed using a computer program EMPIRE for the proton energy range 6-30 MeV. A computer graphical user interface for automatic calculation of production yields taking into account various reaction channels leading to the same final product has been created. The proposed approach allows us to theoretically estimate the amount of 99mTc and its ratio relative to 99gTc and other radioisotopes which must be considered reaction contaminants, potentially contributing to additional patient dose in diagnostic studies.