Radon progeny deliver an average annual absorbed dose of of alpha particles ( ) to…

PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Nuclear medicine, dosimetry and radiotherapy · Nuclear medicine, dosimetry and radiotherapy

The Nucleus Resolved, Ch Dose: kerma, cavity theory, and what energy does to a cell

Problem

Radon progeny deliver an average annual absorbed dose of

D = 5.0\,\mathrm{mGy}

5.5\,\mathrm{MeV}

alpha particles (

L = 85\,\mathrm{keV\,\mu m^{-1}}

) to the basal cell nuclei of a lung airway. Model a nucleus as a sphere of diameter

6.0\,\mu\mathrm{m}

(radius

3.0\,\mu\mathrm{m}

) and density

\rho = 1.0\times10^{3}\,\mathrm{kg\,m^{-3}}

, presenting a circular cross-section

A_{\rm nuc} = \pi r^2

to a passing track. ((a)) Estimate the mean number of alpha tracks crossing a nucleus for this annual dose. ((b)) Using the Poisson distribution, estimate the fraction of nuclei that receive no alpha track at all in a year. ((c)) Estimate the local dose delivered to a nucleus that is actually struck (assume the alpha traverses the full diameter at the stated LET), and compare it with the tissue-average dose.

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