Abstract
Background
The epidemiology of the slightly radioactive contrast agent named Thorotrast presents
a very long latency period between the injection and the development of the related
pathologies. It is an example of the more general problem posed by a radioactive internal
contaminant whose effects are not noteworthy in the short term but become dramatic
in the long period. A point that is still to be explored is fluctuations (in space
and time) in the localized absorption of radiation by the tissues.
Methods
A Monte Carlo simulation code has been developed to study over a 30-year period the
daily absorption of α radiation by μm-sized portions of tissue placed at a distance of 0–100 μm from a
model source, that approximates a compact thorium dioxide source in liver or spleen
whose size is . The biological depletion of the daughter nuclei of the thorium series is taken into
account. The initial condition assumes chemically purified natural thorium.
Results
Most of the absorbed dose is concentrated in a 25-μm thick layer of tissue, adjacent
to the source boundary. Fluctuations where a target region with a volume of 1 μm3 is hit by 3–5 α particles in a day or in a shorter period of time are relevant in a 1–10 μm thick
layer of tissue adjacent to the source boundary, where their frequency is larger than
the Poisson-law prediction.
Keywords
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Article info
Publication history
Published online: February 24, 2014
Accepted:
January 30,
2014
Received in revised form:
January 10,
2014
Received:
June 13,
2013
Identification
Copyright
© 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Inc. All rights reserved.
