In-beam PET measurements of β⁺radioactivity induced by proton beams

Abstract

Our first in-beam PET measurements of the beta+ activation induced by proton irradiation are presented. Monoenergetic proton beams in the energy and intensity range suited for the treatment of deep-seated tumours were delivered by the synchrotron of the Gesellschaft für Schwerionenforschung Darmstadt (GSI). They were stopped in PMMA blocks placed in the centre of the field of view of the positron camera that is installed in the heavy ion tumour treatment facility at GSI. The beta+ activity signal was found to be three times larger than that produced by carbon ions at the same range and applied physical dose. The reconstructed spatial beta+ activity distributions were analysed and compared with the production of positron emitters predicted by a calculation based on experimental cross-sections and on the proton flux given by the FLUKA Monte Carlo code. The shape of the depth-activity profiles was well reproduced by the model and the correlation with the proton range and the depth-dose distributions was carefully investigated. Despite the non-trivial range determination from the beta+ activity distribution in the proton case, our experimental investigation supports the feasibility of an in situ proton therapy monitoring by means of in-beam PET, as already clinically implemented for the monitoring of carbon ion therapy at GSI Darmstadt.

Simulation of proton therapy treatment verification via PET imaging of induced positron-emitters

“…In the depth under 30 cm the production of the isotopes is almost without structure, reflecting the fact that the cross sections remain almost unchanged in the energy range above 100MeV. In this range, the yields calculated with four different cross section data resources reach fairly good agreement with each other, except the 11 C isotope production obtained with the data from reference [11] where the 11 C production is only about 30% of productions obtained with the other data resources, mainly because only one of the three major channels producing 11 C isotope is taken into account [6]. In the depth range between 30 cm and 38 cm where the Bragg peak is located, the calculated productions are significantly different for all three isotopes (see Figures 9-11).…”

Dependence of the Production Yields of Positron Emitters in Proton Therapy on the Cross Section Data Variations

“…In this range, the yields calculated with four different cross section data resources reach fairly good agreement with each other, except the 11 C isotope production obtained with the data from reference [11]. The C 11 isotope production calculated with the data from reference [11] used by Parodi et al is only about 30% of production compared with the other data resources, mainly because only one of the three major channels producing 11 C isotope is taken into account [12]. In the depth range between 30cm and 38cm where the Bragg peak is located, the calculated productions with data resources are significantly different for all three isotopes (see This investigation shows that there is an on going need to develop a library of accurate cross section data for proton and neutron-induced reactions on the elements in human tissue.…”

Patient Study of In Vivo Verification of Beam Delivery and Range, Using Positron Emission Tomography and Computed Tomography Imaging After Proton Therapy

“…The HU-dependent adjustment of electromagnetic and nuclear processes within each material was accomplished using scaling factors to reproduce the calibration curve used by the treatment-planning (TP) dose algorithm, and to account for differences between real and nominal density (6,10). Positron emitter distributions were calculated by internally combining proton fluence with experimental cross sections (12). Besides the main (p, pn) channels on 12 C and 16 O yielding 11 C and 15 O (12), respectively, further proton interactions with N, O, Ca, and P, resulting in 11 C, 13 N, 38 K, and 30 P production, respectively, were included.…”