Experience on the neutron activation of natural/enriched Re,Sm, and Ho nuclides in a reactor for the production of radiotherapeutic radionuclides

In recent years, much effort has been concentrated on the use of Β-emitting radionuclides for the treatment of various cancers. The reports suggested the application of¹⁸⁶Re and¹⁵³Sm as radiotherapeutic radionuclides for the treatment of palliative widespread skeletal métastases, whereas¹⁶⁶Ho was suggested as an agent for radiation synovectomy. Hence, a study on the production of¹⁸⁶Re,¹⁵³Sm, and¹⁶⁶Ho radionuclides was carried out by neutron activation of the appropriate target materials using a Pakistan Atomic Research Reactor (PARR-1) at a neutrons flux of 1 x 10⁴ n/cm² s. These radionuclides were then converted to appropriate radiopharmaceuticals for their use on animals and patients. The targets of natural Re (metal), natural Sm₂O₃, enriched Sm₂O₃ (99.06%), Sm(NO₃)₃ (solid), Sm(NO₃)₃ (liquid), and Ho₂O₃ were irradiated in the PARR-1. After irradiation, the purity of these radionuclides were checked by a multichannel analyzer, Canberra series 85 (MCA) coupled with HPGe detector and then measured in radioisotope calibrator Capintec ionization chamber model CRC-5RH. The effect of the irradiation time and amount of target material was investigated on the production yields of the radionuclides. The results showed an increase in the specific activity of Re with an increase in the irradiation time from 1 to 72 h, whereas a decrease in the specific activity was observed with increase in the amount of Re from 10 to 100 mg. Similar results were obtained for¹⁵³Sm and¹⁶⁶Ho radionuclides. The results further indicated that the specific activity of powder target was much less than the liquid targets for¹⁵³Sm. Their conversion to the appropriate radiotherapeutic radiopharmaceuticals were also carried out by investigating the experimental conditions and acceptable quality of¹⁸⁶Re-HEDP and¹⁵³Sm-EDTMP complexes were prepared. These complexes were then used on animals and patients which showed good performance.