Boron Neutron Capture Therapy

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It was American physicist G.L. Locher who proposed the idea of using neutron capture reactions, in which a 4He nucleus (alpha particle) and 7Li nucleus are emitted when 10B reacts with slow (thermal) neutrons, to destroy cancer cells in cancer treatment, four years after the discovery of the neutron in 1936. Thermal neutrons are captured by a variety of nuclei, but the probability of capture by a 10B (expressed in terms of the capture cross-sectional area in n/cm2·s) is much higher than that of capture by the atoms that constitute human tissue since its cross-section is about 2,000 times larger than that of nitrogen (14N). Furthermore, the track ranges of the two emitted particles are extremely short and do not exceed the diameter of a typical cell. Based on these facts, if there were a 10B-compound that accumulates at sufficient concentrations with a high level of selectivity for cancer cells and tissue, then it would be possible to selectively destroy cancer cells and tissue by irradiating the cancerousregion with neutrons after admin-istering that compound. However, while the probability of this reaction is close to 2,000 times higher than that of the reaction with nitrogen, the extremely high density of nitrogen atoms in tissue makes it necessary for the boron to accumulate in the cancers at levels on the order of several mM. The neutron was discovered by Professor James Chadwick of Cambridge University in 1932. In a famous episode, the husband-and-wife team of Frederic and Irene Joliot-Curie had A neutron source with a high uence rate is essential if the approach is to be applied to cancer treatment. Consequently, any application of the idea had to wait for the emergence of nuclear reactors. Reactors at Brookhaven National Laboratory (BNL) and the Massachusetts Institute of Technology (MIT) were utilized in the rst clinical research. Professors L.E. Farr and W.H. Sweet carried out clinical research targeting malignant brain tumors over the 10-year period beginning in 1951, but the clinical results were poor, with average survival times of less than six months. Concluding that the principal reasons for these outcomes were insufcient selectivity in the accumulation of boron compounds in tumors and the poor quality of the neutron beam, the researchers were forced to focus on resolving these difculties. BNCT research in America was suspended and Japan subsequently picked up where the. Americans left off. World’s rst clinical research (U.S.)Discovery of the neutronJames Chadwick9-10 μm4-5 μm163 keV/μmSlow (thermal) neutrons210 keV/μmAlpha particlesSlow (thermal) neutronsNormal cellCancer cellNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNBBB14N(n, p)14C14N(n, p)14C14N(n, p)14CBBoron Neutron Capture erapyThe birth of BNCTBoron neutron capture therapy, or BNCT, is a treatment technique that allows selective irradiation at the cellular level. The first clinical studies, which began in the U.S., failed to yield good results, but Japan continued the process where the American researchers left off, driving progress to the present day.Proposal of BNCT7Li nucleus1

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