Chapter 7

(226) This chapter presents morphometric data for regions of the human alimentary tract and describes the geometric models used to represent these regions for the purposes of calculating absorbed fractions (AF) and specific absorbed fractions (SAF) for non-penetrating radiation. It also outlines methods for deriving photon SAF values for both the alimentary tract and other regions of the body. A mathematical description of the method of age-dependent dose calculation is presented, and some example AF and SAF values for electrons and alpha particles are discussed. (227) Information is given in this chapter on anatomical parameter values for newborn infants, 1-, 5-, 10-, and 15-year-old children, and adults. The data are consistent with information given in Publication 89 (ICRP, 2002). These data are used to compute values of specific effective energy (SEE; see Section 7.3.1) for each age group. SEE values for intermediate ages are derived by interpolation (linear interpolation by inverse body mass is usually used). Further information on morphometry is given in Annexes A and B. (228) Throughout this chapter, ‘source’ is used to describe those regions where nuclear transformations occur, generally the contents of the lumen of the alimentary tract, or a region within the mucosal lining, and ‘target’ is used to describe regions that contain the radiosensitive cells, i.e. the salivary glands or a specified region within the mucosal lining.