(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: goal of this project is to estimate the range uncertainties of clinical carbon-ion beam analytically and through Monte Carlo (MC) simulation. For this purpose, the spectrum of prompt gamma (PG) rays, that results from nuclear interaction of energetic carbon ions with human tissue and afterward change in their energy due to Doppler shift effect, will be monitored.
Methods: characteristic PG peak of 4.44 MeV emitted via de-excitation of carbon after its nuclear interaction with a hydrogen nucleus was studied. For Doppler blueshifts, the PG frequency is shifted towards higher frequencies and thus Epg shifted > 4.44 MeV; the opposite effect is referred as redshift. These peaks give real-time information of the exact position of the carbon ion since de-excitation happens instantaneously (~10?¹6 sec). We are developing an analytical model, which calculates the relation between the Epg blue, red-shifted, and the incident carbon ion beam energy in the range of 0-450 MeV/nucleus, for the detection angles in the range of 0°-90°. The Bethe formula is used to find the relation between the PG emission and the carbon ion energy loss inside water and soft tissue target materials. In addition, the GEANT4 MC simulation package was used to verify the analytical calculations and monitor the number of PG rays emitted in a given medium.
Results: PG energy is detectable and depends on the initial carbon energy, the detection angle and the shifted PG energy. The relation between these parameters is found based on the analytical mode,l which is in accordance with the theory of Doppler Shift effect. The results are verified by the MC simulations and compared with ICRU 73 report.
Conclusion: the PG emission via Doppler Shift effect, valued information regarding the carbon ion energy and the proper detection angle can be extracted, which could lead in real-time range verification.
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