The size of a Mo-99/Tc-99 generator is determined by the total activity of:

The size of a Mo-99/Tc-99 generator is indeed determined by the total activity of Mo-99 on the column. Mo-99 is the parent isotope that decays into Tc-99, and the generator size needs to accommodate enough Mo-99 to produce the desired amount of Tc-99 through the decay process. The activity of Mo-99 directly influences the amount of Tc-99 that can be eluted from the generator, as Tc-99 is produced at a rate based on the decay of Mo-99. Therefore, having an adequate activity of Mo-99 ensures that the generator can provide a sufficient supply of Tc-99 for clinical use.

The activity of Tc-99 itself is a result of the elution from the generator and does not dictate the size of the generator. Instead, it is a byproduct of the activity present in Mo-99. The administered dose relates to the amount of Tc-99 that a patient receives but does not determine the generator's physical size or capacity. Lastly, elution frequency pertains to how often Tc-99 is drawn from the generator, which can be adjusted based on need, but it does not influence the generator's capacity itself. Thus, understanding the relationship between Mo-