How often must Mo-99 contamination in Tc-99m eluate be measured according to the NRC?

The correct answer indicates that Mo-99 contamination in Tc-99m eluate must be measured only after the first elution. This is rooted in the regulatory framework established by the Nuclear Regulatory Commission (NRC), which requires an assessment of contamination at initial production stages to ensure that any potential release of molybdenum into the technetium-99m product is within safe limits.

Measuring contamination after the first elution allows for an adequate assessment of the radioactive levels, providing reassurance that the subsequent doses being administered to patients remain within acceptable safety thresholds. This requirement reflects an understanding that the primary risk of contamination occurs during the initial elution process when Mo-99 is still present in close proximity to the Tc-99m generator system.

While ongoing monitoring is necessary to ensure product safety, the specific regulation to test only after the first elution is designed to balance safety with practical efficiency in the production process, reducing unnecessary checks that do not significantly change the contamination risk after the first measurement has confirmed acceptable levels.