Theoretical modeling of yields for proton-induced reactions on natural and enriched molybdenum targets

Abstract

Recent acute shortage of medical radioisotopes prompted investigations into alternative methods of production and the use of a cyclotron and ¹⁰⁰Mo(p,2n)(99m)Tc reaction has been considered. In this context, the production yields of (99m)Tc 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 (99m)Tc 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 (99m)Tc 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 (99m)Tc and its ratio relative to (99g)Tc and other radioisotopes which must be considered reaction contaminants, potentially contributing to additional patient dose in diagnostic studies.

Implementation of Multi-Curie Production of 99mTc by Conventional Medical Cyclotrons

“…The content of 96g Tc, 95g Tc, 94m Tc, and 94g Tc was lower using the 97.4% 100 Mo target material, which had a lower content of [92][93][94][95][96][97] Mo. The results agreed with extrapolations from experimental data (24) and showed lower amounts of long-lived impurities than predicted based on Empire III calculations (19). The quantity of 94m Tc was higher than predicted based on theoretic models.…”

“…These include nuclear reactors for neutron enrichment of 98 Mo (11), accelerators to produce spallation neutrons for enrichment of 98 Mo, linear accelerators for the fission of 238 U or the 100 Mo(g,n) 99 Mo reaction (12), and the direct production of 99m Tc through the 100 Mo(p,2n) 99m Tc reaction (13)(14)(15). This latter method was pioneered by Beaver and Hupf in 1971 (13), and experiments were later conducted by Lagunas-Solar (16), Takacs et al (17), and others (18) to measure the cross-sections for the 100 Mo(p,2n) 99m Tc reactions (19).…”

Radioisotopic Purity of Sodium Pertechnetate 99mTc Produced with a Medium-Energy Cyclotron: Implications for Internal Radiation Dose, Image Quality, and Release Specifications

“…As a result, the final formulation of the cyclotron-produced sodium pertechnetate 99m Tc will contain traces of other technetium isotopes, which may contribute to an increase in patient dose and potentially affect image quality. Theoretic calculations on the extent of 99m Tc radioisotopic purity and experimental evaluation of cross sections on thin foils made of enriched molybdenum were conducted previously by others (3,4). This work evaluated the quality of sodium pertechnetate 99m Tc produced with a cyclotron starting from thick (0.58, 0.72, and 0.88 g/cm 2 ) 100 Mo targets.…”

The present and future of medical radionuclide production

“…112], as well as the achievable radionuclidic purity as a function of the isotopic composition of the enriched 100 Mo target [cf . 112,113]. In fact they may both become the deciding factors in the use of the cyclotron-produced 99m Tc.…”

“…will occur as it has been shown in recent studies [cf . 112,113]. The radiochemical separation of 99m Tc from a 100 MoO 3 target could be performed via thermochromatography, as it was done in the case of 94m Tc from a 94 MoO 3 target [114].…”