ИСТИНА

Proton therapy is one of` the advanced modalities of radiation therapy, providing high precision in delivered dose due to the localization of the Bragg peak. Currently, active research is being conducted on the use of ions in therapy, including carbon ions. Owing to their ncreased biological effectiveness and highly precise spatial dose localization, carbon ions may become a successful method of radiation therapy. However, an important issue regarding the applicability of ion beams is the production of secondary neutrons, which are the main source of induced radioactivity and exert a negative impact on healthy tissues. This work was aimed at a comparative assessment of two radiation therapy methods: proton and carbon-ion therapy. Two key parameters were evaluated: dose spatial localization (via Bragg peak width) and radiation safety (i.e., secondary neutron yield). Simulations were performed using the Monte Carlo method (GEANT4), which allows recording of the energy deposition profile along the beam axis and the number of produced secondary neutrons. The behavior of 100 MeV protons and carbon ions with an energy of 275 MeV per nucleon was compared. The analysis considered the same Bragg peak depth in a water phantom, which is regarded as the standard model for dosimetric calculations. The Bragg peak width was estimated using the standard relation FWHM ₩ 2.355 x g.As a result of the simulations: For protons: G = 3.0 mm, FWHM ~ 6.7 mm, for carbon ions: g = 1.3 mm. FWHM ~ 3.1 mm Thus. it can be noted that carbon ions provide a significantly narrower Bragg peak, allowing more accurate conformation of the dose to the tumor volume and better preservation of surrounding healthy tissues. The secondary neutron yield per incident particle was found to be: for protons: 3.96 x 10-2 neutrons per particle, for carbor ions: 1.53 neutrons per particle Consequently, carbon ions produce 38.6 times more neutrons per particle than protons, The spatial precision of the carbon-ion method provides a significantly narrower Bragg peak compared to the proton method, indicating superior accuracy in dose delivery. However, this advantage 1n precision is accompanied by a substantial increase in secondary neutron radiation. Therefore, when selecting a treatment modality, one must consider the anatomical location of the tumor, the availability of specialized neutron shielding, as well as careful dose planning