Biokinetic models for radiopharmaceuticals.

Abstract

Radiopharmaceuticals administered for diagnostic or therapeutic applications in humans are selectively transported into specific organs and tissues of the body, metabolised, and finally excreted according to their biochemical and metabolic properties. Due to the presence of the radioactive label, each of the body regions containing the substance becomes an emitting source (source region), which can also irradiate the neighbouring tissues (defined as target regions). Consequently, each body organ or tissue could receive a radiation dose (absorbed dose) after administration of radiopharmaceuticals even if no activity is present in it. The absorbed dose delivered by incorporated radioactive material is called the internal dose. Direct measurements of the internal dose are not possible for evident practical reasons, so this quantity has to be calculated using a mathematical approach. Such an approach has to take into account that