Decay correction is a method of estimating the amount of radioactive decay at some set time before it was actually measured. Decay correction is a method of estimating the amount of radioactive decay at some set time before it was actually measured. Researchers often want to measure, say, medical compounds in the bodies of animals. It's hard to measure them directly, so it can be chemically joined to a radionuclide - by measuring the radioactivity, you can get a good idea of how the original medical compound is being processed.