Since small amounts of radionuclides are typically being analyzed, the mechanics of manipulating tiny quantities is challenging.  This problem is classically addressed by the use of carrier ions.  Thus, carrier addition involves the addition of a known mass of stable ion to radionuclide-containing sample solution. The carrier is of the identical element but is non-radioactive.  The carrier and the radionuclide of interest have identical chemical properties.  Typically the amount of carrier added is conventionally selected for the ease of weighing such that the accuracy of the resultant weight is within 1%.  For alpha particles, special techniques must be applied to obtain the required thin sample sources.  The use of carries was heavily used by Marie Curie and was employed in the first demonstration of nuclear fission.
Isotope dilution is the reverse of tracer addition.  It involves the addition of a known (small) amount of radionuclide to the sample that contains a known stable element. This additive is the "tracer." It is added at the start of the analysis procedure.  After the final measurements are recorded, sample loss can be determined quantitatively.  This procedure avoids the need for any quantitative recovery, greatly simplifying the analytical process.