BASIS FOR A REVISION OF THE GASTROINTESTINAL-TRACT MODEL

The current ICRP model of the gastrointestinal tract is described in P ublication 30 as a four-compartment model, including the stomach (ST), small intestine (SI), upper large intestine (LLI) and the lower large intestine (LLI) and allows only absorption to the body fluids from th e SI. This model is intended for a reference man which is a 70 kg heal thy adult Caucasian male and does not allow for variation of condition s such as age, gender, the element considered and its physical and che mical form. On the other hand, it has become more important to assess realistic doses to the GI tract because explicit weighting factors hav e been assigned to the oesophagus, the stomach and the colon in ICRP P ublication 60. This paper shows an expanded GI tract model based on pu blished information, including nine compartments. The mouth and oesoph agus as a part of the ingestion pathway are included and the different radiation sensitive cells of the SI are taken into account. In additi on, the absorption of the liquid phase of elements into the blood and the transport of solid phase into the lymphatic system as well as the excretion pathway through the colon is described more accurately by ad ditional compartments.