Speaker
Description
In proton therapy, in-vivo PET range verification requires a comparison of the measured and expected β$^{+}$ activity distribution produced by the proton beam by means of nuclear reactions on the most abundant elements in the body of the patient: C, O, N and, to a lesser extent, P and Ca. The accuracy of the expected activity distributions depends on the accuracy of the Monte Carlo simulations, dominated by that of the underlying cross sections data $^{[1]}$. These are not available in the full energy range of interest (up to 230 MeV) and, when they are, there are sizable discrepancies between data sets. Several studies $^{[2,3]}$ confirm the need for more and better measurements, especially for the short-lived nuclides, for which there are no data whatsoever above 55 MeV $^{[4]}$.
In this context, we intend to improve the knowledge of the production yields of the long- and short-lived β$^{+}$ emitter isotopes of interest. Focusing on the short-lived ones (half-life shorter than the 19 s of $^{10}$C), an experiment has been carried out at KVI-CART (The Netherlands) to measure the most copiously produced isotopes: $^{12}$N (t$_{1/2}$=11 ms) on C, $^{29}$P (t$_{1/2}$=4.14 s) on P and $^{38m}$K (t$_{1/2}$=924 ms) on Ca [3]. The set-up (fig. 1) is designed to measure the production yield at four different energies for each selected primary beam energy. The targets are placed between 3 mm layers of aluminium, which degrade the beam energy and convert the positrons into 511 keV photons which are detected in coincidence by pairs of LaBr$_{3}$ detectors. The experimental setup, simulations and preliminary results of the production cross sections $^{12}$C(p,n)$^{12}$N, $^{31}$P(p,p2n)$^{29}$P and $^{40}$Ca(p,2pn)$^{38m}$K below 150 MeV are presented herein.
