Narrow neutron beam for safer and more effective radiation therapy of tumors

A PhD student from Syria Abdullah Shehada is participating in a research project on upgrading a neutron therapeutic channel based on the TPU cyclotron. This study will improve the effectiveness of neutron therapy in the treatment of malignant tumors by focusing a wide horizontal beam to one centimeter in diameter. A practical part of the study is planned for the early summer of 2019. 

TPU scientists are going to test their computations through experiments. To do this, some changes to the existing design of the biomedical complex for distant neutron therapy should be made. The researchers will use different materials for beam focusing.

Head of the TPU Laboratory for Radioactive Substances and Technologies, As.Prof. Dr. Vladimir Golovkov says:

‘The existing technology operates a wide horizontal beam, the direction of which we cannot control in fact. But by choosing materials for collimator, that is a device that ensures the formation of neutron fluxes in accordance with medical prescriptions, we will be able to focus the scattered neutrons to a narrow beam. A narrow beam allows introducing a safer method of irradiating tumors from different sides.

At present, collimators are made out of polyethylene. We plan to use several materials: hydrogen-containing polymers like polyethylene, materials out of average atomic weight, for example, iron, as well as lead or bismuth. Experiments will be carried out at the cyclotron. Here the objective is to maximize the use of neutrons going out of the source and to focus them in such a way as to ensure a maximum therapeutic effect.’ 

Neutron therapy is a medicine tool created together by oncologists and nuclear physicists. The therapy is possible to run only at the accelerators of charged particles or nuclear reactors where beams of neutrons are generated and directed to the location of malignant tumors. In the city of Tomsk a medicine and biological complex for distant neutron therapy was opened in 1983 on the basis of the TPU cyclotron.

The main advantage of neutron therapy is that unlike gamma and electron therapy neutrons destroy damaged tissue irreversibly, i.e. there is no recurrence after neutron therapy. The negative aspects of neutron therapy are associated with affecting healthy tissues of the body.

‘It is always important that a positive effect exceeds the negative since radiation exposure leads to the damage of healthy tissues. In the research project Abdullah Shehada works on the optimization of neutron beam characteristics, which will minimize the negative effect of neutron therapy,’

adds Vladimir Golovkov.

The physics of neutron generation is as follows: the cyclotron accelerates particles (deuterons), they fall on a beryllium target in which neutrons are released as a result of a nuclear reaction. From the target, they leave like a ‘torch’. It is the torch that needs to be focused, formed into a narrow beam aimed exactly at the damaged tissues. This method will make it possible to get a radiation dose that is as effective as possible for treatment and safer for healthy areas.

Now TPU scientists are working on a system that would help focus the neutron beam literally up to one centimeter in diameter. To achieve this result, it is necessary to do computations taking into account all key factors:  dose distribution, geometric conditions, types of sources, energy, angular distribution, and so on. This is the responsibility of Abdullah Shehada.

‘In my work, I use the Monte Carlo simulation of the motion of each neutron; it is a universal tool for computing the characteristics of neutron fluxes. This is a mathematical method of random numbers that allows simulating what kind of interaction a particle will experience, at what angle it will scatter, what length it will have to the next point of interaction. Such a method is used in particle transport physics and makes it possible to simulate the motion of particles with sufficient accuracy.

For simulating, special software is used to input data. Some variants of simulation have already shown that it is possible to increase the effectiveness of using neutrons by several tens of percent,’ says the PhD student.