Production of 11C, 13N and 15O in proton-induced nuclear reactions up to 200 MeV

Production cross sections of light positron emitters ¹¹C (t_1/2=20.36 min), ¹³N (t_1/2=9.97 min) and ¹⁵O (t_1/2=122 s) have been measured for proton-induced reactions on the main relevant constituents of the human body (C, N and O) from threshold up to 200 MeV of proton incident energy. This has been accomplished by means of two complementary experiments at the clinical proton treatment centers WPE (Essen) and HIT (Heidelberg), both in Germany. In the first case, the multi-foil activation technique was combined with PET imaging, a methodology previously developed at CNA (Seville, Spain). In the second experiment, aimed at energies below 50 MeV, the activation of single foils was measured with conventional LaBr₃ detectors. In both cases the IAEA monitor reaction ^natCu(p,x)⁶³Zn data was used for validation purposes.

The most complete and accurate set of excitation functions for the production of light-positron emitters ¹¹C, ¹³N and ¹⁵O in proton induced reactions on human tissue up to 200 MeV is presented. These data are needed for nuclear reaction model development and are extremely important to improve the accuracy of the PET range verification in proton radiotherapy. Seven excitation functions have been measured: ¹²C(p,x)¹¹C, ¹⁴N(p,x)¹¹C, ¹⁴N(p,x)¹³N, ¹⁴N(p,γ)¹⁵O, ¹⁶O(p,x)¹¹C, ¹⁶O(p,x)¹³N and ¹⁶O(p,x)¹⁵O up to 200 MeV of proton incident energy.