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The pathlength of 7Li and 4He
(alpha particle) is
approximately 5 m m and 8 m m respectively, i.e. approximately the diameter of
a tumor cell (~ 10 m m).
A few alpha particles suffice to destroy a tumor cell. The destructive
effect of the capture reaction would occur mainly in those cancer cells that
have selectively accumulated boron. The normal cells that have not
incorporated significant amounts of boron will not suffer significant
damage.
The total dose deposited by BNCT results from the 10B capture reaction
(large capture cross section), capture reactions with tissue hydrogen and
nitrogen which produce gamma-rays and protons respectively, the gamma
component of the beam, epithermal and fast neutrons. The nature and
distribution of these dose components depend on the source of neutrons, the
filters employed, the concentration and distribution of the boron compounds
and the tissue composition.
This therapy is mainly being used for malignant brain tumors such as
glioblastoma multiforme (GBM) and melanomas of different localizations. The
technique is also beginning to be tested in other tumor types.
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