Dose estimate tchniques

To evaluate the potential deleterious effects of medically useful radioactive materials, the radiation absorbed by the patient during the procedure must be estimated. The quantity of energy imparted to tissue is referred to as the radiation absorbed dose, hereafter referred to as dose. It is a measure of the potential risk to the patient and must be weighed against the probable benefits from the procedure. The intent of this chapter is to define and demonstrate the MIRD formalism used to estimate the dose, to specify the information required to estimate the dose, and to cite sources for this information. Factors that affect the dose include the activity of the administered radiopharmaceutical, its chemical and physical state, the route of administration, and the energy released and imparted to the region for which the dose is calculated (target region) per nuclear transformation (disintegration). The metabolic fate of the radionuclides labeled to the radiopharmaceuticals is variable and sometimes must be evaluated with only limited data from animals and patients. The location, mass, and shape of the target and source regions will also affect the radiation dose. Usually only the mean absorbed dose for an organ as a whole can be calculated, even though the concentration of the radionuclide may be very high in certain regions of the organ. If it is known that a radiopharmaceutical concentrates in a particular region of an organ, the absorbed dose should be calculaated for that region. The absorbed dose should be calculated for the group of organs that are irradiated for the longest period or have the highest concentration of the radiopharmaceutical. The dose to the ovaries, red marrow, and testes should be estimated in order for a dose calculation to be considered adequate