Abstract
The International Commission on Radiological Protection (ICRP) has developed linear differential equations to define the movement of the fraction of inhaled radioactivity that goes to the gastrointestinal tract. These equations are based on assumed biological removal constants for each of three aerosol classes. The graphical method presented here allows the determination of the total number of nuclear transformations that occur in each gastrointestinal compartment when a given class aerosol is inhaled. The method takes into account the radioactive half-life of the isotope, the intestinal absorption fraction, and the aerosol size.