Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

368 CHAPTER 8
Figure 8-9. Model used to describe the kinetics of radionuclides in the body. Abrreviation: GI, gastrointestinal.
(Reproduced with permission from ICRP Publication 30, Part 1: Limits for Intakes of Radionuclides
by Workers. Ann ICRP. 1979; 2(3/4):17. Copyright c○ 1979 International Commission on
Radiological Protection.)
From the particles deposited in the respiratory tract and transported to the GI tract,
the activity transferred to the blood is
(0.5 × 0.3 × f1) + (0.05 × 0.08 × f1) = 0.15 f1,
where f1 represents the fraction of the radionuclide in the GI tract that is absorbed
into the blood. Similar calculations can be made for class W and Y particles. The
results of these calculations are given in Table 8-8.
The GI tract is modeled by four distinct regions, each with its own kinetic parameters,
so that organ doses during passage of radionuclides can be calculated. Similarly,
the organs where the radionuclides are deposited are also modeled by appropriate
equations, usually one or more first-order linear differential equations that allow the
organ doses to be calculated.
TABLE 8-7. Pulmonary Deposition of 1-μm AMAD Particles
REGION PERCENT DEPOSITED
NP 30
TB 8
P 25
Total 63
Abbreviations: AMAD, activity mean aerodynamic diameter; NP, nasopharyngeal; TB, tracheobronchial; P, pulmonary.