Open AccessCarbon-11 and Carbon-12 beam range verifications through prompt gamma and annihilation gamma measurements: Monte Carlo simulations
Author(s) -
Ananta Raj Chalise,
Yujie Chi,
Youfang Lai,
Yiping Shao,
Jin Mu
Publication year - 2020
Publication title -
biomedical physics and engineering express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.333
H-Index - 16
ISSN - 2057-1976
DOI - 10.1088/2057-1976/abb8b6
Subject(s) - monte carlo method , yield (engineering) , range (aeronautics) , annihilation , bragg peak , gamma ray , beam (structure) , nuclear physics , neutron , materials science , ion , carbon fibers , physics , nuclear medicine , irradiation , optics , medicine , statistics , mathematics , composite number , composite material , quantum mechanics , metallurgy
Range uncertainty remains a big concern in particle therapy, as it may cause target dose degradation and normal tissue overdosing. Positron emission tomography (PET) and prompt gamma imaging (PGI) are two promising modalities for range verification. However, the relatively long acquisition time of PET and the relatively low yield of PGI pose challenges for real-time range verification. In this paper, we explore using the primary Carbon-11 (C-11) ion beams to enhance the gamma yield compared to the primary C-12 ion beams to improve PET and PGI by using Monte Carlo simulations of water and PMMA phantoms at four incident energies (95, 200, 300, and 430 MeV u -1 ). Prompt gammas (PGs) and annihilation gammas (AGs) were recorded for post-processing to mimic PGI and PET imaging, respectively. We used both time-of-flight (TOF) and energy selections for PGI, which boosted the ratio of PGs to background neutrons to 2.44, up from 0.87 without the selections. At the lowest incident energy (100 MeVu -1 ), PG yield from C-11 was 0.82 times of that from C-12, while AG yield from C-11 was 6 ∼ 11 folds higher than from C-12 in PMMA. At higher energies, PG differences between C-11 and C-12 were much smaller, while AG yield from C-11 was 30%∼90% higher than from C-12 using minute-acquisition. With minute-acquisition, the AG depth distribution of C-11 showed a sharp peak coincident with the Bragg peak due to the decay of the primary C-11 ions, but that of C-12 had no such one. The high AG yield and distinct peaks could lead to more precise range verification of C-11 than C-12. These results demonstrate that using C-11 ion beams for potentially combined PGI and PET has great potential to improve online single-spot range verification accuracy and precision.