Given potential worldwide shortages of fission sourced 99Mo/99mTc medical isotopes there is increasing interest in alternate production strategies. A neutron activated 99Mo source was utilized in a single center phase III open label study comparing 99mTc, as 99mTc Methylene Diphosphonate ([99mTc]Tc-MDP), obtained from solvent generator separation of neutron activation produced 99Mo, versus nuclear reactor produced 99Mo (e.g., fission sourced) in oncology patients for which an [99mTc]Tc-MDP bone scan would normally have been indicated. Despite the investigational [99mTc]Tc-MDP passing all standard, and above standard of care, quality assurance tests, which would normally be sufficient to allow human administration, there was altered biodistribution which could lead to erroneous clinical interpretation. The cause of the altered biodistribution remains unknown and requires further research.