Investigation of 124I radionuclide production for PET imaging by using a powder target

The aim of this research is cyclotron production of 124I radioisotope (Long-lived positron emitter, suitable for PET imaging) and investigation of its various production methods and calculating the production prerequisites of 124I radioisotope. In this context, cross-section data for the production of medically important radionuclide 124I via major proton, deuteron and alpha induced reactions on Te and Sb targets for the production of 124I were evaluated. The nuclear model codes, TALYS, ALICE and EMPIRE, were used for consistency checks of the experimental data. Therefrom, the integral and differential yields were calculated. This data were utilized to optimize the production processes, involves the choice of an energy range, which maximize the 124I yield and minimize the yield of the impurity 125I. Moreover, the production process was simulated by the MCNPX Monte-Carlo code. On the other hand, the heat transfer on the Te target has been simulated by the COMSOL multiphysics software for the thermal behavior of the target during the irradiation and under the different beam currents, cooling flow rates and target designing. The radioiodine 124I was produced by irradiation of powder natTeO2. The target was irradiated up to with 19 MeV protons at different currents and times. Separation of radioiodine from irradiated tellurium oxide target was investigated by the dry distillation method. According to the obtained results, by some adjustments in the nuclear model parameters, generally good agreement was achieved between calculated and measured excitation functions, for major of investigated reactions. The recommended data should be useful for optimization of various routes for the production of 124I at cyclotrons. At the first irradiation for about 4.4 h at 13.7 μA without separation, 3.33 MBq/μA.h, i.e. 72% of simulation yield was achieved. At the second and third irradiations for 0.7 h at 21.9 μA and 1.5 h at 33.7 μA, the yield of 124I amounted to 2.43 MBq/μA.h and 2.04 MBq/μA.h, respectively, after separation at the EOB. The separation yields were about 72% and 68%, respectively. We have demonstrated that when distilling 124I from natTe, it is sufficient to distil at 750 °C for 20 min. In the best conditions, i.e. 0.7 h irradiation at the current of 21.9 μA, after separation, 1 mCi of radioiodine was achieved and the separation yield was 72%.