Treatment planning assessment of a 9Be(d,n}-based neutron source for a real Glioblastoma Multiforme case

HERRERA, M.S.; CAPOULAT, M.E.; GONZÁLEZ, S.J.; MINSKY, D.M.; KREINER, A.J.

Tsukuba

Congreso; 15th International Congress on Neutron Capture Therapy; 2012

International Society for Neutron Capture Therapy

As an alternative to the traditional epithermal neutron source. we propose the use of an 8-rnicron thick Be target bombarded with 1.45 MeV deuterons. From a neutronic point of view, the nuclear reaction provides a harder neutron spectrum (average energy of about 1.7 MeV, up to maximally ~5.8 MeV for the proposed bombarding energy), compared to the 7Li(p,n) reaction. However. it should be mentioned that there is a strong population of highly excited states in 10B, accompanied by the emission of very low energy neutrons. whose production is maximized with respect to neutrons of higher energies by using a thin target (see the other contribution of Capoulat et al. in these proceedings]. In addition, other main advantages of this reaction lie on the thermal and mechanical superiority of Be over metallic Li, together with the absence of residual radioactivity, that allow to simplify most of the complications related to target engineering design. Moreover. the low-bombarding energies involved imply a significant advantage concerning to voltage requirements for design and construction of an accelerator devoted to BNCT.Our previous studies based on a Snyder head phantom showed the potential of the 9Be(,d,n) reaction as an epithermal neutron source to treat brain tumors with BNCT.In this work we evaluate the performance of the proposed neutron source for the treatment of a real patient with diagnosed glioblastoma multiforme. From the corresponding computed tomography, the patient's head with a 4.2 cm3 tumor located within the occipital lobe of the brain was modeled by 11025 voxels of 1 cm3 each, where the absorbed dose rate was computed via MCNP5. The neutron beam direction in the simulation was determined based on the location  of the lesson using the NCTPlan treatment planning code. The results derived from the simulations were assessed setting the maximum normal brain dose to 1 l Gy-Eq and using different figures of merit. such as the maximum mean and minimum doses delivered to normal organs and tumor and 3-D dose distributions by means of their corresponding dose-volume histograms. In addition, normal tissue complication probability (NTCP) was computed to evaluate possible early skin damage. Preliminary results show that a significant mean tumor dose of 42 Gy-Eq can be delivered with the proposed scheme while keeping the average whole brain close lower than 4 for an irradiation time of about 60 minutes. These promising results strengthen the prospects for a potential use of the 9Be(d,n) reaction for the treatment of brain tumors with BNCT