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This paper presents the results of studying changes in the neutron flux in the neck phantom of a person with a tumor. As is known, the flux density of these neutrons in the target (in the tumor) depends on the distance and elemental composition of the tissue they must travel to the target. In the medical application of radiation, this elemental characteristic of tumors is important for determining the absorbed dose, which is fundamental for radiotherapy. Therefore, a study was conducted on the elemental imbalance in patients with breast cancer, which is associated with carcinogenic processes responsible for the development and growth of malignant neoplasms of the breast [1]. Among certain elements, Mg, Al, P, S, Cl, K, Mn, Zn and Pb in the group with malignant neoplasms, the level of these elements was significantly higher than in the group of healthy people, with a significance level of 0.05. Although this is not statistically significant, the effective atomic number (Zeff) and electron density (𝜌e) in the group with malignant neoplasms were slightly higher than in the healthy group, which causes a difference in the mass coefficients of attenuation of the photoelectric effect and interactions with the birth of pairs in the two subjects. Healthy tissue with lower Zeff and 𝜌e values dominated the maximum EABF values, while malignant breast tissue with higher Zeff and 𝜌e values dominated the minimum values. Differences in the parameters of photon radiation between the two groups indicate that these two groups will behave differently when interacting with photons. In [2], the elemental composition of tumor tissue and blood serum was studied under conditions of experimental carcinogenesis and during the treatment of animals with an inoculated malignant testicular tumor with platinum—containing drugs (cisplatin and platyserine); a combination of cytostatic therapy and the intake of a phytosorption complex - dietary supplement "Berezhnik". It has been shown that there is an accumulation of Al, Ca, and Zn, Pt in the testicular tumor tissue with a simultaneous decrease in the content of Ca, P, and Mg in the blood serum. The maximum changes in the elemental composition of tumor tissue and blood serum were noted against the background of platyserine therapy in combination with Berezhnik dietary supplements: the highest content of Pt in tumor tissue; the maximum increase in the concentration of Fe, Zn, P, and Ca in blood serum. In [3], it was possible to observe significant changes in the distribution of concentrations of P, S, K, Ca, Mn, Fe, and Cu in distant tissues caused by the presence of tumor cells. Among other results, this work makes it possible to study the modulation of distant tissues caused by the presence of a primary tumor. This can be achieved by evaluating several elements with known biological significance, which makes it possible to study various biological processes involved in the development of cancer. In (4), it was found that the concentrations of 52 elements ranged from 0.4 ng/g of tissue (Lu, Pd, and Tm) to 1,658,000 ng/g (Na), 1,951,000 ng/g (P), and 2,495,000 ng/g (K). Thirty-eight of the 52 (73.1%) of the elements showed approximately equal concentrations in the tumor and adjacent normal lung tissues of the patients. The concentrations of nine elements (K, P, Mg, Zn, Rb, Cu, Se, Cs, and Tl) in tumor samples were significantly higher than in paired normal lung tissues, and five elements (Na, Fe, Cr, Cd, and Ge) showed reduced concentrations in cancer samples compared with similar ones. normal lung tissues. The low iron content in the tumor samples was associated with a history of smoking, while the low chromium content was associated with the histological structure (squamous cell carcinoma) of the patients. The results show that measuring the concentrations of elements in both tumor and paired normal tissues is important for understanding the role of these elements in carcinogenesis, and therapeutic approaches aimed at normalizing these elements. Therefore, to study the dependence of the neutron flux density on the concentration of elements, studies were conducted on changes in the neutron flux density during the passage of neck phantoms. The simulated calculations were performed using the MCNP-4C program. Figure 1 shows the geometry of calculating the human neck phantom. For calculations, this phantom is represented in the form of a cylinder with a tumor inside; the following elemental composition of human tissues was used, taken from the ICRU 46 (Goorley) data bank [5]. Such calculations were also carried out for neck phantoms. Figure 1 shows the geometry of neck phantoms for MCNP calculations.
Fig. 1. Geometry of the human neck phantom for MCNP calculations: 1-tumor, 2-neck, 3-external collimator, 4- horizontal reactor channel
The neck phantom had the shape of a cylinder and the following dimensions: Rcl = 5cm, Rcanser = 1.2, lcl = 10 cm. At the beginning, the tumor was located in the left edge of the phantom, then this tumor was gradually moved to the right edge and changes in the neutron spectrum were studied. The analysis of these spectra to study changes in the flux density in the tumor, depending on its location in the phantom, shows that the neutron flux with an energy of 10-7 MeV does not change with penetration into biological tissue up to 4 cm, it doubles when the tumor is removed by 4 cm, decreases by 3 orders of magnitude with 6 cm removal of the tumor, then it changes slightly. The neutron flux with an energy of 10-6 MeV changes slowly and increases at 8 cm distance, neutrons with an energy of 10-5 MeV almost do not change, and neutrons with energies of 10-4-10-2 MeV change very slightly, the flux densities of 1-10 MeV neutrons change slightly. The analysis of photon spectra shows that the density of photons with energies 0.01-0.1 has at a distance of 2 cm, and drops sharply at 8 cm distance. The flux of photons with energies of 0.5 and 10 MeV is almost unchanged. The photon flux with an energy of 1 MeV up to 4 cm does not change; at 6 cm, the distance of the tumor from the edge of the phantom decreases by 1.3 orders of magnitude. These calculations show that when using an epithermal neutron beam, it is possible to form a spectrum to create the maximum dose in neck tumors with GdNRT. This requires further studies with sophisticated 3D geometry, with the introduction of Magnevist, in order to study the pharmacokinetics of the drug in tumors and ensure radiation planning taking into account the pharmacokinetics of the drug in human neck tumors.
Acknowledgement (Financial support): The work is financed by the state budget of the Republic of Uzbekistan.
- Abayomi M. Olaosun, David O. Olaiya Elemental Characterization and Radiation Parameters of Malignant and Healthy Breast Tissues , Journal of Trace Elements and Minerals 2 (2022) 100023.
- N.E. Gelfond, E.V. Starkova, O.V. Shuvaeva, I.E. Michurin, Elemental composition of tumor tissue and blood serum in conditions of experimental carcinogenesis and its correction BULLETIN OF the Siberian Branch of the Russian Academy of Medical Sciences, No. 1 (115), 2005, pp. 28-32.
- Xin Cheng,| Yong‐Chun Zhou, Bo Zhou, Yun‐Chao Huang, | Gui‐Zhen Wang, |Guang‐Biao Zhou. Systematic analysis of concentrations of 52 elements in tumor and counterpart normal tissues of patients with non‐small cell lung cancer. Cancer Medicine. 2019;8:7720–7727
- Stephen Juma Mulware, Comparative Trace Elemental Analysis in Cancerous and Noncancerous Human Tissues Using PIXE. Journal of Biophysics Volume 2013, Article ID 192026, 8 pages
- ICRU Report 63 "Nuclear Data for Neutron and Proton Radiotherapy and for Radiation Protection". 2001. https://bioone.org/journals/radiation-research/volume-156/issue-2/0033-7587_2001_156_0223_2.0.CO_2/Nuclear-Data-for-Neutron-and-Proton-Radiotherapy-and-for-Radiation/10.1667/0033-7587(2001)156[0223:]2.0.CO;2.short
