Quantification of radiation dose from short-lived positron emitters formed in human tissue under proton therapy conditions

Excitation functions of nuclear reactions leading to the soft-radiation emitting radionuclides45Ca,49V and204Tl in beam collimator materials used in proton therapy

Summary. Cross sections of nuclear reactions leading to the formation of the soft-radiation emitting radionuclides45Ca (T1/2=163 d; β−=260 keV),49V (T1/2=330 d;Kα=4.51 keV) and204Tl (T1/2=3.78 a; β−=763 keV) in proton induced reactions on titanium and lead, respectively, often used as collimators in proton therapy facilities, were measured for the first time over the energy range extending up to 200 MeV. Use was made of the stacked-foil technique. Elaborate radiochemical separations were performed and the radioactivity of the products was determinedviaanticoincidence beta counting, liquid scintillation counting or X-ray spectrometry. The experimental data were compared with the results of nuclear model calculations using the codes ALICE-IPPE and TALYS. In general good agreement was obtained. In the case of204Tl, however, the calculated values from ALICE-IPPE in the energy region above 80 MeV deviated considerably from the experimental data, possibly due to strong contributions of multiple particle emission reactions.