TECHNETIUM-94M-TEBOROXIME - SYNTHESIS, DOSIMETRY AND INITIAL PET IMAGING STUDIES

Technetium-94m (T1/2 = 53 min) allows the in vivo study of technetium radiopharmaceuticals with positron emission tomography (PET). PET prov ides a quantitative assay of radioactivity with excellent temporal and spatial resolution, revealing biodistributions that were previously a vailable only through in vitro assay methods. Technetium-94m, produced by the proton irradiation of natural molybdenum on an 11 MeV cyclotro n, was extracted with an electrochemical etching technique. Technetium -94m-pertechnetate was prepared to make the myocardial perfusion agent teboroxime in an identical manner as (TcO4-)-Tc-99m. The increased ab sorbed radiation dose requires a sevenfold reduction in administered a ctivity compared to Tc-99m-teboroxime. Eleven clinical PET studies wer e performed and visually compared to N-13-ammonia. The clearance half- time for Tc-99m-teboroxime was almost-equal-to 8 min, with a peak myoc ardial extraction of almost-equal-to 3% of the injected dose into a 40 0-g heart. These results confirm the potential of Tc-99m PET for quant itatively studying the pharmacokinetics of new, and old, technetium ag ents in man.