Self-absorption Effects on Electron Absorbed Fraction in the Anterior Nose

Moussa, Hanna; Eckerman, K.F.; Townsend, L.

doi:10.1093/oxfordjournals.rpd.a006836

Cited by 3 publications

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“…The materials used in the estimations were air and water (a surrogate for tissue). The effects of attenuation by dust particles in the ICRP 66 cylinder model have been addressed elsewhere (Moussa et al 2002).…”

Section: Methodsmentioning

confidence: 99%

“…Although electrons traveling through the interior of the dust particle would likely be deflected before emerging from the dust particle, the analysis is simplified by assuming straight-line trajectories (Moussa et al 2002). …”

Section: Geometrical Modeling and Simulationmentioning

confidence: 99%

“…The density is 3 g cm Ϫ3 , and the element mass fractions are: H (0.021), C (0.016), O (0.577), Al (0.050), Si (0.271), K (0.013), Ca (0.041), and Fe (0.011). Following Moussa et al (2002), the range calculation is carried out using…”

Section: Parameters Usedmentioning

confidence: 99%

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Dust Particle Size Effects on Absorbed Fraction Values in the Anterior Nose

Moussa

2007

Health Physics

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The respiratory tract model introduced in Publication 66 of the International Commission on Radiological Protection (ICRP) includes consideration of extrathoracic airways, referred to as the ET region. This region comprises the anterior nose and the posterior nasal passages, larynx, pharynx, and the mouth. The deposition of inhaled particles in the airways depends on the thermal and aerodynamic properties of the particles and equations are presented to calculate the deposition efficiency in the various regions of the tract. In its dosimetric model the ICRP assumes that none of the energy emitted by the deposited source is lost in the particles itself (i.e., no self attenuation) and the deposition is assumed to be on the inner surface of the airway of the anterior nose. Therefore, the effects of various dust particle sizes on the energy deposition in the epithelium as characterized by the absorbed fraction in the anterior nose region were not addressed in ICRP 66. Since radioactive particulate matter is carried in air within dust particles, this subject should be addressed. In this paper the effects of dust particle sizes (various equivalent volume diameters) on the absorbed fraction to the anterior nose are studied using a truncated cone model for the anterior nose. The results indicate that attenuation in the dust particles has a significant effect on the electron absorbed fraction. This effect depends on the dust particle size and the energies of the electrons emitted by the radionuclides carried within dust particles.

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Section: Methodsmentioning

confidence: 99%

Section: Geometrical Modeling and Simulationmentioning

confidence: 99%

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Dust Particle Size Effects on Absorbed Fraction Values in the Anterior Nose

Moussa

2007

Health Physics

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

Moussa¹,

Eckerman²,

Townsend³

2006

Radiation Protection Dosimetry

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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.

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Electron Absorbed Fractions Based on a New Model of the Anterior Nasal Passage

Moussa

Kf²,

Lw³

2004

Health Physics

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In a previous work we reported that the fraction of the electron energy absorbed in the basal cell layer of the anterior nasal passages was not very sensitive to changes in the surface area or radius of the cylindrical model adopted in Publication 66 of the International Commission on Radiological Protection. These absorbed fraction data are used in calculation of the dose to a 10-microm-thick basal cell layer located at a depth of 40 microm in the epithelial cell layer of the extrathoracic (ET1) region. However, these data may only be applicable to the assumed cylindrical geometry and may not be valid for more realistic ET1 geometries. The nose differs in size and shape from one person to another, its shape is not cylindrical but closer to a truncated elliptical cone, and in most humans the nostrils are elliptical in shape. We propose herein a more realistic geometry model, the frustum of a cone, for the anterior nose region (ET1) as an alternative to the cylinder model provided in ICRP 66. The results of absorbed fraction calculations using MCNP4B with the new model are reported. These absorbed fractions are compared to the values previously obtained using the MCNP4B code and a cylindrical model (10 cm2 surface area). We also investigate the effects of changing the size of the truncated cone to represent variations due to sex and age.

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Self-absorption Effects on Electron Absorbed Fraction in the Anterior Nose

Cited by 3 publications

References 0 publications

Dust Particle Size Effects on Absorbed Fraction Values in the Anterior Nose

Dust Particle Size Effects on Absorbed Fraction Values in the Anterior Nose

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

Electron Absorbed Fractions Based on a New Model of the Anterior Nasal Passage

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