Linear-Quadratic Model for Planning Neutron Therapy with the Use of U-120 Cyclotron

Abstract

Purpose: To estimate the feasibility of using linear-quadratic model (LQM) for planning neutron therapy regimens by the criterion of early radiation-induced reactions. Material and methods: The LQM, which described the reaction of tissues to fractionated irradiation, was used. The results obtained were compared with similar results found on the basis of the TDF model successfully used for neutron therapy planning. Results: The LQM parameters αn and βn for radiation induced skin damage were found. The dependence of a single dose of neutrons on the number of therapy sessions was obtained. This dependence was in good agreement with the analogous dependence found by the TDF model, which indicated the correctness of the method for calculating it. When using LQM for planning neutron therapy, the issue related with the time intervals between sessions was considered. For this purpose, the comparative calculations of the ratio of the total effect, determined by the LQM, and the TDF factor were carried out. The difference between the compared values did not exceed 6 %, thus allowing the time interval for planning neutron therapy using LQM to be excluded. Two methods to control the damage to normal tissue using LQM were considered. The first method was based on the evaluation of part of the used tolerance of the irradiated tissue, and the second one was carried out by transferring the applied dose fractionation regimen of neutron therapy to the isoeffective standard regimen of photon therapy. Conclusion: It was shown that LQM can be used for planning neutron therapy regimens in cancer patients by the criterion of early radiation-induced reactions. The results obtained extend the potential of radiobiological planning of neutron therapy and can serve as a basis for the development of the method of using LQM in prediction of late radiation-induced complications.