Induced nuclear reactions: processes – systems – and elements – Moderator or reflector component structure for a fission...
Patent
1996-06-10
1997-12-30
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Moderator or reflector component structure for a fission...
376906, 428650, G21C 500, G21K 100, A61N 510
Patent
active
057039186
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a moderator material used for moderation of high-velocity neutrons, in particular of fission neutrons, to epithermal neutrons.
Further, the invention concerns a novel use of the moderator material for neutrons in accordance with the invention.
With respect to the prior art related to the present invention, reference is made to the cited paper Proceedings of an International Workshop on Neutron Beam Design, Development, and Performance for Neutron Capture Therapy, held Mar. 29-31, 1989, at the Massachusetts Institute of Technology, in Cambridge, Mass., Edited by Otto K. Harling, John A. Bernard and Robert G. Zamenhof, Plenum Press, New York.
The boron neutron capture therapy (BNCT) is based thereon that, to the patient, through the blood circulation, an agent is administered that seeks its way into the cancer tissue and to whose molecule components have been attached that include boron atoms. A neutron flux is directed at the location of the cancer tissue, the neutrons in said neutron flux being absorbed into the boron and splitting the boron to lithium and helium, which destroy exactly cancer cells very locally, but which destroy any other tissue very little.
In BNCT, the formula of the boron neutron capture is as follows: (93.9%)>.sup.7 Li+gamma+0.48 MeV
The boron neutron capture therapy produces quite a little strain on the patient. Surgical operation and anaesthesia are not needed. For the therapy team, the radiation strain does not differ in any way from administration of conventional radiological therapy.
In BNCT, slow or thermal neutrons have been used, whose depth of penetration is so little that the patient's cranium must be opened for the time of the therapy. On the contrary, epithermal neutrons of higher velocity are not moderated for capture by boron atoms until in the interior of the head, in which case the cranium does not have to be opened.
In boron neutron capture therapy, attempts are made to produce a distribution of the flux of thermal neutrons in the area of the body part to be treated, for example the head, which distribution of flux has a rather wide maximum sufficiently deep in the area to be treated. It is well known that this aim is reached best if epithermal neurons are passed from an external source to the body part to be treated, which neutrons are not thermalized until in the interior of the body. The neutron source best suitable for the therapy purpose is a research reactor, which produces primarily high-velocity fission neutrons. They must be moderated under control to epithermal neutrons, to the energy range of 1 eV . . . 10 keV, so that the proportion of high-velocity neutrons remains sufficiently low. As is known from prior art, many different materials have been suggested for the moderator material, such as metallic aluminum, aluminum oxide, aluminum fluoride, silicon, and equivalent.
Aluminum fluoride is a subliming compound, which is available as a porous powder, but out of it, it is impossible to prepare a dense material free of pores. Porosity is a drawback in principle, for it increases the necessary material thickness and brings the treatment point unduly far from the primary source, thereby lowering the useful intensity that can be achieved.
The object of the present invention is to provide a novel moderator material for neutrons by whose means the above drawbacks can be eliminated.
In view of achieving the objectives stated above and those that will come out later, the moderator material in accordance with the invention is mainly characterized in that the principal components of the moderator material are aluminum fluoride and aluminum metal, which have been formed into a dense composite substantially free of pores.
According to the present invention, the moderator material defined above is used in boron neutron capture therapy (BNCT) of cancer tissues.
In the following, the invention will be described in detail with reference to the schematic illustration in the accompanying drawing, which is an illustration of principle of BNCT therapy b
REFERENCES:
patent: 3995163 (1976-11-01), Colditz
patent: 4362696 (1982-12-01), Brehm, Jr. et al.
patent: 4566989 (1986-01-01), Radford et al.
patent: 4675150 (1987-06-01), Russell, Jr. et al.
patent: 5015863 (1991-05-01), Takeshima et al.
Auterinen Iiro
Hiismaki Pekka
RADTEK OY
Wasil Daniel D.
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