A novel 99mTc delivery system using (n,gamma)99Mo adsorbed on a large alumina column in tandem with Dowex-1 and AgCl columns.

99Mo of specific activity 7.4-14.8GBq (200-400mCi)/g was adsorbed on a 'jumbo' alumina column (40g, 90mm(H) x 20mm (dia.); 50g, 65mm(H) x 35mm(dia.). [99mTc]TcO4-, eluted with 50-70ml normal saline and applied to a tiny column of a strong anion exchanger, Dowex-1 x 8, 10-15 mg, 8-12 mm(H) x 1 mm(dia.). Pertechnetate was eluted from the Dowex-1 column with 5-6 ml of 0.2M Nal followed by washing with 1.5-1.8 ml water. Iodide was removed from this eluate by passage through a 1 g AgCl column (12 mm (H) x 8 mm (dia.)). The final product, pertechnetate, was recovered in 6.5-7.8 ml, while the NaCl content was close to that of normal saline. Each elution operation was complete in approximately 45 min. The mean practical yield was approximately 86% (n = 5). Closed cycle operation with sterile connecting tubes and multi-way stop-cocks was practised. The quality of the [99mTc]NaTcO4 thus obtained complies with the specifications applicable for radiopharmaceutical use. The major merit over other post-elution concentration methods is that the new procedure can function nearly independently of the volume of the primary eluate (in normal saline) from the alumina column generator (ACG). 99mTc generators containing as much as 80-100 g alumina for holding 14.8-18.5GBq (400-500 mCi) 99Mo (at the reference time) are feasible using approximately 15 mg Dowex-1 bed mass. A relatively user-friendly--cum--producer-friendly 99mTc generator system has been demonstrated making use of the inexpensive and easy to prepare (n,gamma)99Mo. The method is also applicable for the more costly 188W-188Re generator.