MCNP simulation of the dose distribution in liver cancer treatment for BNC therapy

The Boron Neutron Capture Therapy (BNCT) is based on selective uptake of boron in tumour tissue compared to the surrounding normal tissue. Infusion of compounds with boron is followed by irradiation with neutrons. Neutron capture on ¹⁰B, which gives rise to an alpha particle and recoiled ⁷Li ion, enables the therapeutic dose to be delivered to tumour tissue while healthy tissue can be spared. Here, therapeutic abilities of BNCT were studied for possible treatment of liver cancer using thermal and epithermal neutron beam. For neutron transport MCNP software was used and doses in organs of interest in ORNL phantom were evaluated. Phantom organs were filled with voxels in order to obtain depth-dose distributions in them. The result suggests that BNCT using an epithermal neutron beam could be applied for liver cancer treatment.     

Variable neighbourhood search for bandwidth reduction

The problem of reducing the bandwidth of a matrix consists of finding a permutation of rows and columns of a given matrix which keeps the non-zero elements in a band as close as possible to the main diagonal. This NP-complete problem can also be formulated as a vertex labelling problem on a graph, where each edge represents a non-zero element of the matrix. We propose a variable neighbourhood search based heuristic for reducing the bandwidth of a matrix which successfully combines several recent ideas from the literature. Empirical results for an often used collection of 113 benchmark instances indicate that the proposed heuristic compares favourably to all previous methods. Moreover, with our approach, we improve best solutions in 50% of instances of large benchmark tests.     

Specific energy distribution within cytoplasm and nucleoplasm of a typical mammalian cell due to various beta radionuclides

The use of beta radionuclides for treatment in radiotherapies leads for a need of better understanding of interactions and local energy depositions of beta particles within tissue and tissue equivalent media. The aim of this work is to determine microdosimetric quantities for various radionuclides. Specific energy, z, and its distribution, $ f(z) $ , mean specific energy, $ \bar{z} $ , and its standard deviations, $ \sigma \left( {\bar{z}_{f} } \right) $ , were evaluated for typical single cell where nucleus is the cellular region of interest. Three possible positions of radionuclides were taken into account—cellular membrane, cytoplasm and nucleoplasm. Taking these regions as the source of radiation, microdosimetric quantities were calculated for beta emitting radionuclides: ¹⁹¹Os, ¹⁹⁹Au, ¹⁷⁷Lu, ⁶⁷Cu, ⁷⁷As, ¹³¹I, ¹⁸⁶Re, ³²P, ¹⁸⁸Re and ⁹⁰Y. It was found that low range beta emitters have the largest efficiency and can deliver radiation doses up to 1 mGy per decay. Determination of the specific energy and its distribution for radionuclides is a useful start in order to determine beta emitters for a particular radionuclide therapy.