How many hours does it take for Tc-99m activity to reach maximum levels after elution from a Mo99/Tc99m generator?

To determine how long it takes for Tc-99m to reach maximum activity levels after elution from a Mo-99/Tc-99m generator, it is important to understand the behavior of the isotopes involved. The elution process typically yields a peak concentration of Tc-99m shortly after it is extracted from the generator.

Tc-99m exhibits a relatively short physical half-life of about 6 hours, meaning that it will decay significantly over time. Immediately after elution, the activity of Tc-99m is at its highest, and it will gradually decrease as it decays.

Moreover, the Mo-99, the parent isotope, has a half-life of approximately 66 hours, which allows continuous supplies of Tc-99m; however, Tc-99m will not require an extensive delay to reach its peak given the nature of the extraction and decay. It typically achieves maximum activity levels rapidly, often within the first few hours post-elution, rather than requiring a full day or multiple days.

The correct answer reflects that while Tc-99m quickly reaches significant activity levels right after elution, it does not take as long as 24 hours or more, which is more reflective of the general operational time frame