Bombarding a tumor with a neutron beam is a promising technique of radiation therapy. However, this kind of therapy is not widely used, because it needs large-scale neutron accelerators, requiring separate buildings.

Russian researchers have developed a neutron generator, which needs only 1 square meter of space. The device can be installed in any room with radiation protection, in other words, all large Russian cities can get its own facility for cancer treatment. About a week ago first experimental compact neutron generator has been launched in Obninsk.

A neutron generator works on deuterium ²H and tritium ³H, heavy isotopes of hydrogen. A powerful electric discharge ionizes deuterium molecules, which fall into electron and deuteron, consisting of a proton and neutron. Deuteron reacts with tritium, and they form helium ⁵He, which quickly breaks into helium atom and a neutron. The reaction is exothermic, thus releasing a neutron with energy of 13-15.5 megaelectron-volt, depending on an angle.

This reaction is commonly used in many neutron generators; however, new device provides collection of excess tritium by a titanium target, thus avoiding a bulky tritium evacuation system. This innovative solution allows making neutron generators much smaller, than existing ones.

Neutron therapy works the following way: cancer cells are damaged by energy of neutrons. Particles fly with a high speed and collide with molecules inside cancer cells, thus damaging them. A neutron beam, for instance, can cause water molecules to form protons and hydroxyl radicals, which react with biological polymers and cause cell death.

 

 

Generator developers say that the new device can also be used for another kind of treatment, known as neutron-capture therapy. During neutron capture therapy heat neutrons with low energy get absorbed by boron atoms, which have been introduced inside a cell beforehand. Absorption results in release of high amount of energy and formation of a lithium atom and an alpha particle. This kind of therapy is highly effective and is almost harmless for healthy tissues, usually surrounding a tumor, however, it is used extremely rarely due to technical difficulties with making neutrons with given energies.

New neutron generator, like any other drug or treatment, will be first tested on cell cultures. This stage will demonstrate how efficient radiation of the device is in killing tumor cells and how it affects healthy cells and tissues. Following test stage will be performed with laboratory animals – rats or mice. This stage is aimed at collecting as much information as possible about optimal dosage of radiation and at planning treatment schemes. Researchers plan to study effects of a combination of neutron therapy with gamma particles. Mentioned combination eliminates side effects of pure neutron radiation and helps cure “radio-resistant” tumors, with which gamma radiation gives no effect.

Medical and biological tests will help improve the new neutron generator, and after installing protection from radiation and tests of large animals, the device will be ready for clinical trials. The device will cost about 40-45 million rubles, which is the price of a magnetic resonance imaging scanner.

Science & Technologies

Kizilova Anna