Cyclotron production of Ac-225 / Bi-213 for targeted alpha therapy

Due to its physical characteristics the generator system Ac-225 / Bi-213 appear to be a very suitable and convenient method of producing an alpha-emitter for targeted alpha therapy. However, the production of Ac-225 is not so trivial and that is why not a great quantity of this interesting isotope is available for clinical applications. Till recently it was produced by the decay of Th-229, which itself is generated by the decay of U-233 (half life of 159200 years). Alternative method of production of Ac-225 is by irradiating a target of Ra-226 with protons in a cyclotron through (p,2n) reaction. By making use of our isotopic yields data we have shown that, through (p,2n) reaction on Ra-226, the thick-target production yields of Ac-225 would be around 1.1 x 1010 Bq, 1.85 x 1010 Bq and 2.04 x 1010 Bq respectively at proton bombarding energies of 20, 30 and 34 MeV respectively at incident proton currents of 100 μA, but irradiation time of only one day which is a lot more practical than the quoted 10 days by others. Similarly production yields of Ac-225 through the (d,3n) reactions on Ra-226 have also been estimated to be 4.2 x 109 Bq, 1.1 x 1010 Bq and 1.4 x 1010 Bq respectively at deuteron energies of 20, 30 and 34 MeV for irradiation time of 1 day at beam intensities of 100 μA. The production yields data is presented in graphical form from which the production of Ac-225, from a thick, moderately thick or even a thin Ra-226 target can be obtained for any irradiation conditions. Furthermore , production yield curves of various other isotopes being simultaneously produced through (p,n), (p,3n), (d,n) and (d,2n) reactions on Ra-226, are also presented from which any impurities or unwanted activities, could be estimated. All these curves would help to select the optimum irradiation conditions for producing Ac-225 with cyclotrons