Simulation of thermal responses of 125TeO2 solid target to energetic proton bombardment from cyclotron when fabricating 124I nuclear medicine

With nuclear medicine receiving greater attention due to its unique characteristics in both diagnostics and therapeutics during recent decades, finding a highly controllable fabrication method becomes more urgent. The radioisotope 124I (T1/2=4.18d; Eβ+=2.13MeV; Iβ+=25%) has gained plentiful interests in the medical usages such as functioning imaging of cell proliferation in brain tumors using [124I]iododeoxyuridine (IUdR), imaging of immunoreactions in tumors using 124I-labelled monoclonal antibodies, the in-vivo imaging of 124I-labelled tyrosine derivatives, and the classical imaging of thyroid diseases with 124I, among others. Furthermore, it is because that thermal response of target during the fabrication process may affect the production of 124I to some extent and needs thorough investigations. Hence, the compact cyclotron located in the Institute of Nuclear Energy Research was employed in this study to generate 20MeV protons to irradiate TeO2 solid targets in which the radioisotopes 124I were produced through the 125Te(p, 2n)124I nuclear reaction. In addition, the widely-used ANSYS computer code was adopted to theoretically analyze thermal responses of TeO2 to irradiation cases with variations in ion beam current and its thermal conductivity. The results indicate that TeO2 temperature is strongly dependent on its thermal conductivity and ion beam current. In particular, TeO2 surface temperature is extremely sensitive to the air-gap size between TeO2 and target holder. Thus the target holder is suggested to be re-designed in order to prevent TeO2 from melting and a high efficiency production of radioisotopes 124I for nuclear medical diagnostics can be successfully achieved. (author)