For how long should a dose calibrator test be carried out if it starts with 50 mCi of 99mTc-pertechnetate?

The half-life of technetium-99m (99mTc) is approximately 6 hours. When performing a dose calibrator test, the purpose is to verify the accuracy and performance of the calibration over time as the radionuclide decays.

Starting with a dose of 50 mCi of 99mTc-pertechnetate, you can calculate how long it would take for the radioactivity to decay to a specific level. The amount of radioactivity halves every 6 hours. By projecting this decay, you can determine how many half-lives pass within a certain duration.

To find out how long it would take for the activity to decay significantly, you can consider that after 6 hours, the activity drops to 25 mCi, after 12 hours to 12.5 mCi, after 18 hours to 6.25 mCi, and after 24 hours to 3.125 mCi. After 30 hours, it would have decayed to about 1.56 mCi, and by 36 hours, down to about 0.78 mCi.

Thus, if the testing needs to cover a timeframe where a substantial decay is observed and the test is useful in confirming the calibrator