Clinical Trial with Sodium 99mTc-Pertechnetate Produced by a Medium-Energy Cyclotron: Biodistribution and Safety Assessment in Patients with Abnormal Thyroid Function

Abstract

A single-site prospective open-label clinical study with cyclotron-produced sodium ^99mTc-pertechnetate (^99mTc-NaTcO₄) was performed in patients with indications for a thyroid scan to demonstrate the clinical safety and diagnostic efficacy of the drug and to confirm its equivalence with conventional ^99mTc-NaTcO₄ eluted from a generator. Methods:^99mTc-NaTcO₄ was produced from enriched ¹⁰⁰Mo (99.815%) with a cyclotron (24 MeV; 2 h of irradiation) or supplied by a commercial manufacturer (bulk vial eluted from a generator). Eleven patients received 325 ± 29 (mean ± SD) MBq of the cyclotron-produced ^99mTc-NaTcO₄, whereas the age- and sex-matched controls received a comparable amount of the generator-derived tracer. Whole-body and thyroid planar images were obtained for each participant. In addition to the standard-energy window (140.5 keV ± 7.5%), data were acquired in lower-energy (117 keV ± 10%) and higher-energy (170 keV ± 10%) windows. Vital signs and hematologic and biochemical parameters were monitored before and after tracer administration. Results: Cyclotron-produced ^99mTc-NaTcO₄ showed organ and whole-body distributions identical to those of conventional ^99mTc-NaTcO₄ and was well tolerated. All images led to a clear final diagnosis. The fact that the number of counts in the higher-energy window was significantly higher for cyclotron-produced ^99mTc-NaTcO₄ did not influence image quality in the standard-energy window. Image definition in the standard-energy window with cyclotron-produced ^99mTc was equivalent to that with generator-eluted ^99mTc and had no particular features allowing discrimination between the ^99mTc production methods. Conclusion: The systemic distribution, clinical safety, and imaging efficacy of cyclotron-produced ^99mTc-NaTcO₄ in humans provide supporting evidence for the use of this tracer as an equivalent for generator-eluted ^99mTc-NaTcO₄ in routine clinical practice.

Keywords: cyclotron; efficacy; safety; sodium 99mTc-pertechnetate; thyroid imaging.