Estimation of a radiation weighting factor for 99mTc

Decaying (99m)Tc does not only emit a gamma ray (140.5 keV), but also low-energy Auger and conversion electrons. These electrons cause a serious problem in the determination of a radiation weighting factor for (99m)Tc due to their extremely short range in tissue. Therefore, for comparison ultrasoft...

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Bibliographic Details
Published inRadiation protection dosimetry Vol. 122; no. 1-4; p. 80
Main Authors Pomplun, E, Terrissol, M, Kümmerle, E
Format Journal Article
LanguageEnglish
Published England 01.12.2006
Subjects
Algorithms
Computer Simulation
DNA - chemistry
DNA - radiation effects
DNA Damage
Dose-Response Relationship, Radiation
Electrons
Models, Chemical
Radiation Dosage
Radiometry - methods
Technetium - chemistry
X-Rays
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Summary:Decaying (99m)Tc does not only emit a gamma ray (140.5 keV), but also low-energy Auger and conversion electrons. These electrons cause a serious problem in the determination of a radiation weighting factor for (99m)Tc due to their extremely short range in tissue. Therefore, for comparison ultrasoft X rays are used here, which deposit their energy mainly via the photoeffect thus also initiating low-energy photoelectrons. Monte Carlo computer codes provided electron emission spectra of (99m)Tc and subsequent track structure calculations simulated the induction of DNA damage of different degrees of complexity. For the modelling of ultrasoft X rays carbon K photons with an energy of 270 eV were selected, for which experimental results are available from the literature. On average, four electrons were found to be emitted per (99m)Tc decay. Simulation of DNA damage revealed a nearly identical spectrum of primary strand breaks for (99m)Tc and C-K radiation. On this basis, a total radiation weighting factor of 1.2 was evaluated for (99m)Tc.
ISSN:0144-8420
DOI:10.1093/rpd/ncl405