Medical Radiology and Radiation Safety. 2021. Vol. 66. № 6. P. 93–98

Determination of Monitor Doses in Neutron  Therapy  Using the U-120 Cyclotron

V. А. Lisin

Cancer Research Institute, Tomsk National Research Medical Center, Tomsk, Russia

Contact person: Valery Andreevich Lisin, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.


Purpose Analyze the various methods for determining the monitor doses in neutron therapy using the U-120 cyclotron and to choose the monitoring method that provides the highest accuracy in dose delivery to the tumor.

Material and methods  The distributions of the absorbed dose of the therapeutic beam from the U-120 cyclotron were measured in a tissue-equivalent medium using the differential method, in which two ionization chambers with different sensitivity to neutron radiation were used. A comparison of radiation effects on tissues using various techniques of determining the monitor doses was made. The linear-quadratic model was used to assess responses to ionizing radiation. 

Results  Dosimetry studies revealed that the therapeutic beam of the U-120 cyclotron contains concomitant gamma radiation, the contribution of which to the total neutron-photon dose increases with increasing depth of the irradiated medium. The presence of gamma radiation in the neutron beam dictate the need to find the correct method for monitoring neutron therapy. A comparison of radiation effects on the tumor tissue using different techniques of determining the monitor doses was made.  It was found that at equal neutron-photon doses, the neutron dose in the tumor changed depending on its depth. It can lead to an incorrect conclusion about the effectiveness of neutron therapy depending on a single dose as well as in relation to various dose fractionation schedules. 

 Conclusion  The analysis of the results obtained showed that the problem can be most accurately solved using a technique in which the monitor coefficient and monitor doses are determined from the distribution of the neutron dose, taking into account the contribution of the gamma radiation dose to the total neutron-photon dose. 

Key words: neutron therapy, monitor doses, linear quadratic model

For citation: Lisin VА. Determination of Monitor Doses in Neutron  Therapy  Using the U-120 Cyclotron. Medical Radiology and Radiation Safety. 2021;66(6):93–98.

DOI: 10.12737/1024-6177-2021-66-6-93-98


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Conflict of interest. The author declare no conflict of interest.

Financing. The study had no sponsorship.

Contribution. The article was prepared by one author.

Article received: 07.06.2019. 

Accepted for publication: 20.09.2021.