Study of the time and space distribution of beta+ emitters from 80 MeV/u carbon ion beam irradiation on PMMA

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms (Impact Factor: 1.19). 02/2012; 283. DOI: 10.1016/j.nimb.2012.04.021
Source: arXiv

ABSTRACT Proton and carbon ion therapy is an emerging technique used for the treatment
of solid cancers. The monitoring of the dose delivered during such treatments
and the on-line knowledge of the Bragg peak position is still a matter of
research. A possible technique exploits the collinear $511\ \kilo\electronvolt$
photons produced by positrons annihilation from $\beta^+$ emitters created by
the beam. This paper reports rate measurements of the $511\ \kilo\electronvolt$
photons emitted after the interactions of a $80\ \mega\electronvolt / u$ fully
stripped carbon ion beam at the Laboratori Nazionali del Sud (LNS) of INFN,
with a Poly-methyl methacrylate target. The time evolution of the $\beta^+$
rate was parametrized and the dominance of $^{11}C$ emitters over the other
species ($^{13}N$, $^{15}O$, $^{14}O$) was observed, measuring the fraction of
carbon ions activating $\beta^+$ emitters $A_0=(10.3\pm0.7)\cdot10^{-3}$. The
average depth in the PMMA of the positron annihilation from $\beta^+$ emitters
was also measured, $D_{\beta^+}=5.3\pm1.1\ \milli\meter$, to be compared to the
expected Bragg peak depth $D_{Bragg}=11.0\pm 0.5\ \milli\meter$ obtained from

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