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Calculation of Energy-Deposition Distributions and Microdosimetric Estimation of the Biological Effect of a 9C Beam

Davide Mancusi (Institutionen för teknisk fysik, Nukleär teknik) ; Lembit Sihver (Institutionen för teknisk fysik, Nukleär teknik) ; K. Niita ; Q Li ; T. Sato ; H. Iwase ; Y. Iwamoto ; N. Matsuda ; Y. Sakamoto ; H. Nakashima
Radiation and Environmental Biophysics (0301-634X). Vol. 48 (2009), 2, p. 135-143.
[Artikel, refereegranskad vetenskaplig]

Among the alternative beams being recently considered for external cancer radiotherapy, C-9 has received some attention because it is expected that its biological effectiveness could be boosted by the beta-delayed emission of two alpha particles and a proton that takes place at the ion-stopping site. Experiments have been performed to characterise this exotic beam physically and models have been developed to estimate quantitatively its biological effect. Here, the particle and heavy-ion transport code system (PHITS ) is used to calculate energy-deposition and linear energy transfer distributions for a C-9 beam in water and the results are compared with published data. Although PHITS fails to reproduce some of the features of the distributions, it suggests that the decay of C-9 contributes negligibly to the energy-deposition distributions, thus contradicting the previous interpretation of the measured data. We have also performed a microdosimetric calculation to estimate the biological effect of the decay, which was found to be negligible; previous microdosimetric Monte-Carlo calculations were found to be incorrect. An analytical argument, of geometrical nature, confirms this conclusion and gives a theoretical upper bound on the additional biological effectiveness of the decay. However, no explanation can be offered at present for the observed difference in the biological effectiveness between C-9 and C-12; the reproducibility of this surprising result will be verified in coming experiments.



Denna post skapades 2010-02-01. Senast ändrad 2013-10-29.
CPL Pubid: 111285

 

Institutioner (Chalmers)

Institutionen för teknisk fysik, Nukleär teknik (2006-2015)

Ämnesområden

Kärnfysik

Chalmers infrastruktur