Comparison of the Light Charged Particles on Scatter Radiation Dose in Thyroid Hadron Therapy

Bachground: Hadron therapy is a novel technique of cancer radiation therapy which employs charged particles beams, ۱H and light ions in particular. Due to their physical and radiobiological properties, they allow one to obtain a more conformal treatment, sparing better the healthy tissues located in proximity of the tumor and allowing a higher control of the disease.  Objective: As it is well known, these light particles can interact with nuclei in the tissue, and produce the different secondary particles such as neutron and photon. These particles can damage specially the critical organs behind of thyroid gland. Methods: In this research, we simulated neck geometry by MCNPX code and calculated the light particles dose at distance of ۲.۱۴ cm in thyroid gland, for different particles beam: ۱H, ۲H, ۳He, and ۴He. Thyroid treatment is important because the spine and vertebrae is situated right behind to the thyroid gland on the posterior side. Results: The results show that ۲H has the most total flux for photon and neutron, ۱.۹۴۴E-۳ and ۱.۷۶۶۶E-۲, respectively. Whereas ۱H and ۳He have best conditions, ۸.۸۸۶۰۹E-۴ and ۱.۳۵۴۳۱E-۳ for photon, ۴.۹۰۵۰۶E-۴ and ۴.۳۴۰۵۷E-۳ for neutron, respectively. The same calculation has obtained for energy depositions for these particles.Conclusion: In this research, we investigated that which of these light particles can deliver the maximum dose to the normal tissues and the minimum dose to the tumor. By comparing these results for the mentioned light particles, we find out ۱H and ۳He is the best therapy choices for thyroid glands whereas ۲H is the worst.

Keywords:

Hadron therapy , thyroid gland , secondary particles , photon and neutron flux , energy deposition