Theoretical substantiation of biological efficacy enhancement for β‐delayed particle decay ⁹C beam: A Monte Carlo study in combination with analysis with the local effect model approach

Abstract

Collectively, the increased local doses and clustered damages due to the decayed particles emitted from deposited (9)C particles led to the RBE enhancement in contrast with the (12)C beam. Thus, the enhanced RBE effect of a (9)C beam for a simplified tumor model was shown theoretically in this study.

β-delayed multiple-particle emitters minibeam radiation therapy: first dosimetric evaluation with Monte Carlo simulations

“…This section compares stable ion species ( 7 Li, 12 C, 40 Ar) and their radioactive counterparts ( 8 Li, 9 C, 31 Ar). Two irradiation schemes and ctc values were evaluated for each ion species.…”

“…Theoretical dosimetric characterizations of argon MBRT were performed by Peucelle et al [17] and by Gonzalez et al [20] showing advantageous dose distributions favoring normal tissue preservation. The radioactive ion chosen for our evaluation was 31 Ar, a drip-line nucleus. 31 Ar decays via four different branches: via β + in 31 Cl (branching ratio = 0.22), via β + , p in 30 S (branching ratio = 0.68), via β + , 2p in 29 P (branching ratio = 0.09) and via β + , 3p in 28 Si (branching ratio = 0.0007).…”

“…The radioactive ion chosen for our evaluation was 31 Ar, a drip-line nucleus. 31 Ar decays via four different branches: via β + in 31 Cl (branching ratio = 0.22), via β + , p in 30 S (branching ratio = 0.68), via β + , 2p in 29 P (branching ratio = 0.09) and via β + , 3p in 28 Si (branching ratio = 0.0007). For the first three mentioned decay branches, the produced heavy ions are not stable and will continue to emit positrons (isobaric chain) until they reach a stable state.…”

“…Six different ions were simulated: 7 Li, 8 Li, 9 C, 12 C, 31 Ar, 40 Ar. The energies of the primary beams, summarized in Table 2, were chosen to have a range in water of ~7 cm.…”

“…The use of RIB for therapeutical application was proposed at the heavy ion medical accelerator in Chiba (HIMAC) [28]. Studies conducted at HIMAC with 9 C showed advantages in terms of the distributions of biologically effective dose and cell survival along the beam penetration as compared with stable 12 C [29][30][31]. In the case of MBRT, the nuclear fragments resulting from the β-delayed multiple-particle breakup reaching the valleys regions might be biologically very relevant [17,18,20], particularly for tumor control [32].…”