Cyclotron production of technetium radioisotopes

Objectives We seek to demonstrate the practicality of the direct production of Tc-99m from isotopically enriched Mo-100, using existing cyclotron technology, from bench to bedside by developing an appropriate target system and chemical isolation method for Tc-99m.

Methods We have developed a novel electrochemical plating technique to produce coatings of Mo-100 onto a range of target plate materials. The Mo-100 targets were tested in-beam to ensure stability, and the Tc-99m production metrics (yields, isotopic composition, etc.) were established. In addition, a process for target dissolution and automated separation was developed and the chemical, radiochemical and radionuclidic purity of the cyclotron-produced pertechnetate were determined.

Results >30 µm coatings of Mo-100 were successfully plated onto Cu, Al, Ta, Ni and Rh backings, achieving around 85% theoretical density. Low-current (0.17 to 10 hour, 1 to 20 µA, 18-8 MeV) irradiations on test targets produced Tc-99m with yields of 526 MBq/µAh and 99m/99g ratios between 21 and 28%. After oxidative dissolution of the Mo-100 target the Tc-99m was separated using a custom-designed separation module. Two separate purification approaches based on anion exchange technology were developed and employed as a means to isolate Tc-99m from the bulk Mo-100 and target material; achieving over 90% extraction efficiencies. The resulting pertechnetate was found to conform to the quality control specifications required of clinical-grade generator-produced pertechnetate. Future work will examine the incorporation of cyclotron-produced Tc-99m into commercial radiopharmaceutical kits.

Conclusions Direct on-target production of Tc-99m from isotopically enriched Mo-100 targets is a viable approach to enable regional distribution of sufficient quantities of pertechnetate in the event of future supply disruptions.

Research Support This research is supported through NSERC (90%) and CIHR (10%)