153Sm, an attractive therapeutic radionuclide, was produced by neutron activation of both natural Sm2O3 and 98% enriched 152Sm2O3 targets. The production logistics and radionuclidic purity aspects of 153Sm obtained using both these targets are discussed with respect to the intended end use for metastatic bone pain palliation (MBPP) in terminal cancer patients and radiation synovectomy (RS) of medium size joints. The specific activity of 153Sm obtained was around 11 GBq x mg(-1) (approximately 300 mCi x mg(-1)) and 44 GBq x mg(-1) (approx. 1200 mCi x mg(-1)) from natural and enriched targets, respectively. The level of the long-lived radionuclidic impurity burden in 153Sm obtained from the natural Sm2O3 targets, namely, due to 154Eu (5 Bq x MBq(-1) 153Sm (5 nCi x mCi(-1) 153Sm)) and 155Eu (75 Bq x MBq(-1) 153Sm (75 nCi x mCi(-1) 153Sm)), appears low enough not to pose a problem, both in the palliative treatment of terminal cancer patients (at 1.85-2.22 GBq (50-60 mCi) dose) as well as in RS (at 74 MBq (2 mCi) dose). The 154Eu content in 153Sm from the enriched target was comparable, while, as expected, the level of 155Eu was nearly two orders of magnitude lower. There is a notable overall advantage of 153Sm over the use of 186Re, the other radionuclide of interest for the same purposes.

About a 4-fold increase in radioactive concentration of Tc was obtained (cf. approximately 10-12 ml normal saline is required for the elution of Tc from the gel column). Generators containing up to 22.2 GBq (600 mCi) Mo in 6-7 g ZrMo gel column (35 x 13 mm) were prepared and a radioactive concentration of Tc up to 4 GBq x ml (110 mCi x ml) was obtained on the first day of use. The overall recovery of Tc was >90%, Mo breakthrough was 10 to 10% and the duration of concentration was 3-5 min. The chemical impurity in terms of Al, Mo and Zr was <10 ppm each. The same procedure for the concentration of pertechnetate was applied to generators with 12-15 g ZrMo gel beds to obtain a higher capacity Tc gel generator, with similar findings.

m Tc gel generator / Zirconium molybdate / Hospital radiopharmacy evaluation / Microwave drying / Centralized radiopharmacy Summary As a sequel to the process standardization for small scale production of " m Tc gel generators based on zirconium molybdate-"Mo, extensive evaluation of the generator performance including for clinical use was carried out and is reported here. Following the procedure standardized by us earlier, 9 lots of "Mo were converted into ZrMo gel adopting aseptic practices and two different techniques for drying the ZrMo cake -heated air at 60-80 °C and microwave drying at 385 watts. 14 generators, containing up to 18.5 GBq "Mo, supplied for clinical use and evaluated at two hospital radiopharmacies showed satisfactory generator performance. The applicability for preparing larger capacity generators for centralizeid radiopharmacies and feasibility to achieve reduced process time and ease of control by using microwave oven drying have also been established.

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