Purpose: In boron-10 neutron capture enhancement of fast neutron irradiation (BNCEFN), the dose enhancement is correlated to the 10B concentration and thermal neutron flux. A new irradiation technique is presented to optimize the thermal neutron flux.

Methods And Materials: The coupled FLUKA and MCNP-4A Monte Carlo codes were used to simulate the neutron production and transport for the Nice and Orleans facilities.

Results: The new irradiation technique consists of a 20-cm lead blocks additional collimator, placed close to the patient's head, which is embedded in a pure graphite cube. A 24-fold thermal neutron flux increase is calculated between a 5 x 5 cm2 primary collimated field, with the patient's head in the air, and the same field size irradiated with the optimum irradiation technique. This increase is more important for the p(60)+Be Nice beam than for the p(34)+Be Orleans one. The thermal neutron flux is 2.1 x 10(10) n(th)/Gy for each facility. Assuming a 100 microg/g 10B concentration, a physical dose enhancement of 22% is calculated. Moreover, the thermal neutron flux becomes independent of the field size and the phantom head size.

Conclusion: This technique allows conformal irradiation of the tumor bed, while the thermal neutron flux is enhanced, and spreads far around the tumor.

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http://dx.doi.org/10.1016/s0360-3016(98)00478-7DOI Listing

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