Purpose: To develop a new Prompt Gamma Spectroscopic (PGS) technique that enhances the production of PG rays emitted from ¹²C* and ¹⁶O* de-excitations, by injecting a non-radioactive element in the tumor area. Positive results will lead in accurate monitoring of proton range and target-tissue characteristics during the treatment.
Methods: The Tool for Particle Simulations (TOPAS) Monte Carlo (MC) package was used to simulate 10⁷ proton histories of 75 MeV and 100 MeV incident in a co-centric cylindrical geometry. The outer cylinder was filled with water, and the inner cylinder was filled with water plus 0.01%-25% fractions in weight of the elements ¹⁹F, ¹⁷O, ¹²C, ¹H, and ¹²⁷I, respectively. We identified the characteristic peaks in the PG spectra, and then we assessed the PG enhancement of the 4.44 MeV peak (P1) resulting from ¹²C* de-excitations, and the 6.13 MeV peak (P2) resulting from ¹⁶O* de-excitations.
Results: For the 75 MeV incident proton beam the maximum P1 and P2 enhancement was 20.1% and 3.71% when 0.01% of ¹²⁷I and 1% ¹⁹F enriched the inner cylinder placed at surface, with respect the outer cylinder. For 100 MeV incident proton beam the maximum P1 enhancement was 8.88% when 0.01% ¹⁹F was added to the inner cylinder. When the inner cylinder was placed at depth of 2 cm for the 75 MeV incident proton beam, and at 5 cm for the 100 MeV incident proton beam, with respect to the outer cylinder, the PG enhancement dropped to half. The Bragg peak was not affected by the enrichment of the inner cylinder with the studied elements.
Conclusion: It was found that the enhancement of PG production yield is possible by enriching the inner cylinder with the used non-radioactive elements. This is an ongoing study and simulations with more tissue-like materials such as brain-tissue are in progress.
Not Applicable / None Entered.
Not Applicable / None Entered.