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Investigation of Prompt Gamma Yield From C-11 and C-12 Irradiation

A Chalise1* , Y Chi1, Y Shao2 , M Jin1 , (1) University of Texas at Arlington, Arlington, TX, (2) UT Southwestern Medical Center, Dallas, TX


(Tuesday, 7/31/2018) 10:00 AM - 10:30 AM

Room: Exhibit Hall | Forum 9

Purpose: Prompt gamma (PG) imaging and PET for hadron-therapy are two popular beam verification techniques. However, low signal to background ratio is a major challenge for online application. Radioactive beam sources are of great interest for its signal enhancement for online verification. This study is to investigate PG yield performance with radioactive C-11 beams and conventional C-12 beams.

Methods: Geant4 was used for simulation with a water phantom. A physics list was used to govern particle transport, nucleon interaction, dose deposition and PG yield. C-11 beam with 6 charges was studied at four beam energy levels in comparison with C-12. The comparison of energies was performed using the same particle penetration depth. Energy and time of flight (TOF) of the produced PG events were studied. Based on a TOF window of 2.7 ns and lower-bound energy cutoff of 2MeV, depth displacements between PG and dose profiles were compared.

Results: A linear relation was found for the energy at the same penetration depth for C-11 and C-12, while the average dose peak position was found within 1 mm. For the TOF distribution, it was found the mean value of C-11 was 0.2~0.3 ns less than C-12 with the similar spread. After applied the TOF window and energy cutoff, 80% drop-off point of the PG peak was found within 0.6 mm difference between C-11 and C-12. The absolute PG yield of C-11 at the PG peak range is about 7% less than C-12 on average, but the peak of C-11 was sharper than that of C-12 for the normalized yield. The average displacements between PGs and corresponding brag peak were comparable for C-11 and C-12.

Conclusion: PG yield for the C-11 ion-beam is similar to that of the C-12 ion-beam, which could open a door for combined online PG imaging and PET.


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