Advances in the production, processing and microPET image quality of technetium-94m.

This work involves the production, processing and imaging of the short-lived, rarely used positron emission tomography (PET) radionuclide technetium-94m (94mTc). Our procedures are an extension of methods reported in the literature and are detailed within. A key modification was the development of a single step that combines purification and concentration of an aqueous 94mTc-pertechnetate solution, which both reduces processing time and increases the final concentration of the solution. Additionally, a convenient method for the direct recovery of 94mTc into an organic solvent was developed, eliminating the solvent transfer step needed for organic syntheses using 94mTc. Each of these advances potentially extends the scope of syntheses possible with this short-lived radionuclide. To explore the imaging potential of 94mTc, we carried out phantom imaging studies on small-scale high-resolution PET scanners to estimate the limitations of detection associated with 94mTc and PET. Preliminary studies demonstrate that useful images can be obtained with modern image reconstruction algorithms when using a correction for the cascade gamma ray contamination.

Concentration of 99mTcO4-/188ReO4- by a single, compact, anion exchange cartridge.

BACKGROUND: This paper describes a simple and inexpensive post-elution anion exchange cartridge system for the concentration of 99mTcO4-/188ReO4-. METHOD AND RESULTS: The system is based on generator elution with a mixture of 0.7 M acetic acid and 0.0225 M sodium chloride instead of physiological saline to provide high specific volume solutions of 99mTc and 188Re from 99Mo-99mTc and 188W-188Re generators, respectively. The passage of the bolus through an amine-type (Accell Plus QMA Sep-Pak) anion exchange cartridge results in trapping of the microscopic levels of the pertechnetate or perrhenate. Subsequent elution of the anion exchange cartridge with 2 ml of saline then provides high specific volume solutions of pertechnetate or perrhenate. CONCLUSION: This new approach works effectively to obtain concentrated solutions of 99mTcO4- and 188ReO4- from commercially available alumina based Mo-Tc and W-Re generators, respectively.

Post-elution concentration of 99TcmO4- by a single anion exchanger column: II. Preparation and evaluation of jumbo alumina column chromatographic generator for 99Tcm.

We report on the preparation and evaluation of a large size (jumbo) alumina column (approximately 40 g, 90 x 20 mm) chromatographic generator and post-elution concentration of 99Tcm using a single column of a weak anion exchanger. The generator was eluted with approximately 40 ml of a modified single salt buffer solution of 1:1 v/v 0.025 M or 0.05 M NH4OAc:0.7 M AcOH. This eluate was then passed through a small column of DEAE cellulose, a common weak anion exchanger, to trap 99TcmO4-, which was recovered by elution in 6 ml of normal saline. This amounts to a 5- to 7-fold increase in radioactive concentration (RAC) of 99Tcm, when compared to the RAC on direct elution with normal saline from the same jumbo alumina column generator. The overall yield of 99Tcm was in the range of 70-90%. 99Mo breakthrough was 10(-3)-10(-4)%, radiochemical purity was > 98%, and chemical purity, in terms of Al and Mo content, < 10 ppm each. The compatibility of pertechnetate obtained by this method for preparing 99Tcm labelled formulations such as Tc-MDP and 99Tcm-ethyl cysteinate dimer was found to be satisfactory. These promising results open up the feasibility of using (n, gamma) 99Mo adsorbed on a large (40-60 g) alumina column as a relatively more user-friendly source of 99Tcm in comparison to methyl ethyl ketone extraction, and as a producer-friendly process in comparison to the zirconium molybdate gel method.