Charged particle equilibrium effects on the electron absorbed fraction in the extrathoracic airways

Abstract

Estimates of the dose to the extrathoracic airway (nasal vestibule) from inhaled beta-emitting radionuclides, obtained using the respiratory tract model presented in Publication 66 of the International Commission on Radiological Protection, frequently predict that the basal cells in this region are the most highly irradiated tissues of the body. The dose to the basal cells is averaged over a layer of tissue 10 microm thick located at a depth of 40 microm into the airway assuming that charged particle equilibrium exists. Since the target (basal cell layer) is very small and thin (10 cm(2) area and 10 microm thickness), charged particle equilibrium does not exist. In this work the effect on the absorbed fraction of the lack of charged particle equilibrium is investigated.

The minimum crystal size needed for a complete diffraction data set

“…Perhaps the most important caveat is that photoelectron escape formally violates the fundamental dosimetric principle of charged-particle equilibrium (CPE; Attix, 1986;Moussa et al, 2006), making simulation results difficult to interpret. The concern over violating CPE arises because more than half of the energy 'deposited' by a photoelectron is not in the form of ionizations but rather charge-neutral electronic excitations.…”