A look at the problem of exposure of the population caused by X-ray diagnostics: approaches to analysis and forecasting

The article is devoted to the analysis of limitation of dose load on the population as a result of radiological researches. It is especially actual and represents rather high scientific and practical interest. In this regard, it is very important to have information about the state of the dose load of the population in separate regions and to rank types of diagnostics by the amount of their contribution to the total dose of medical exposure. The aim of the work was to study the state of dose load of the population of Zaporizhzhia region due to X-ray diagnostics, to develop approaches to analysis and forecasting regarding its limitation. Analytical, statistical calculation and logical generalization methods were used in the course of the work. We used the results of studies carried out in accordance with the regional “Program for the Protection of the Population of Zaporizhzhia Region from the Effect of Ionizing Radiation. The authors analyzed scientific publications (15 sources), including 9 Ukrainian and 6 foreign on the relevance of the problem of exposure of the population caused by X-ray diagnostics. The analysis of the results allowed to determine that in 2010-2014 the radiation dose of the population of Zaporizhzhia region due to X-ray diagnostics averaged 0.92 mSv year-1, in 2015-2016 the dose increased and amounted to 0.96 mSv year-1. The proposed approach to the analysis makes it possible to summarize and model data on radiological studies of the population over a long period of time, to identify persistent trends in the contribution of different types of radiation diagnostics to the dose of medical radiation. All this is necessary for the development, first of all, of measures to reduce the frequency of radiography, its replacement by other diagnostic methods. Priority tasks aimed at reducing the dose load of the population due to X-ray examinations are proposed.

One task of routing jobs in high radiation conditions

The problem of sequential bypass of megalopolises is investigated, focused on the problem of dismantling a system of radiation hazardous objects under constraints in the form of precedence conditions. The radiation impact on the performers is assessed by the doses received during movements and during the performance of dismantling works. The route problem of minimizing the dose load of workers carrying out dismantling in one or another sequence of operations is considered. The procedure for constructing an optimal solution using a variant of dynamic programming is investigated. On this basis, an algorithm is built, implemented on a PC. Examples of the numerical solution of a model problem for the minimum dose load are given.

Radiation-Hygienic Monitoring in Potentially Radon-Hazardous Territories

Modern radioecological studies to assess the effect of natural radiation on the human body have shown that at the moment of development of society, the main contribution to the exposure of the population is made by natural sources of ionizing radiation, while from 50 to 90 % of the dose load are caused by the gas radon-222 (222Rn) and daughter products of its decay. This paper presents the results of radiation-hygienic monitoring of the potentially radon-hazardous territory of the city of Baley, Trans-Baikal Territory. The measurement of the volumetric activity of radon (OARn) was carried out in the premises of residential and public buildings by the integral method using track exposure meters REI-4. According to the indicator of the equivalent equilibrium volumetric activity of radon (EROARn), a radiation-hygienic assessment of the premises and the calculation of potential dose loads on the population living in this territory were carried out. Studies have shown that OARn in residential and public buildings depends on the geological characteristics of the territory, on the design and design of buildings and structures, and on the building materials used. It was found that the main criterion for assessing the potential radon hazard of territories is the value of OARn in rooms on the 1st floors of buildings. According to the degree of potential radon hazard, the territory of the city of Baley can be conditionally divided into 3 types: 1 type – the territory located on a geological fault; Type 2 – the southern part of the city, represented by sedimentary rocks; Type 3 – the northern part of the city, represented by rocks of the basic gabbroid group with a low content of natural radionuclides. The types of buildings and structures and the type of building materials affect the dose load, but do not determine it.

Analysis of Dose Load on a Pregnant patient in Radiotherapy of Oropharal Cancer

Purpose: The assessment of the dose load on a pregnant patient during irradiation of the oropharyngeal tumor at different distances from the border of the irradiated field, including at the level corresponding to the position of the fetus, based on phantom measurements.Material and methods: To calculate the exposure plan, the ECLIPSE planning system with the AAA algorithm was used. Irradiation was performed on a LinacClinaciX (Varian, USA) with a nominal photon energy of 6 MeV. The tissue equivalent phantom Alderson–Rando was used to assess the dose load on the fetus.Results and conclusions: It was shown that the total absorbed dose at the level and below the diaphragm (the level of the fetus) at a distance of more than 40 cm from the border of the irradiation field for the entire course of radiation therapy turned out to be significantly less than the permissible limits indicated in the literature and amounted from 41.71 to 14.03 mGy.

Comparison of dosimetry parameters of three-dimensional conformational radiation therapy and volumetric modulated arc therapy on the example of treatment of a patient with salivary gland adenocarcinoma

An optimal choice of radiation therapy method is the main prerequisite for successful completion of treatment. Continuous analysis of radiation therapy methods’ advantages and comparing their parameters and dose load in typical cases will increase the treatment efficacy and reduce the unavoidable load on critical organs. The purpose was to check the plans of treatment by volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiation therapy (3D-CRT) methods, make their comparison and identify the advantages using an example of a treatment design for a patient treated at the Daily Radiotherapy Hospital of the Kazakh Institute of Oncology and Radiology (Almaty, Kazakhstan). Results: The presented illustrations of the process planning and the numerical analysis of the dose load on critical organs show VMAT advantages for radiation therapy of salivary gland cancer: optimal coverage, sparing load on critical organs and healthy tissues, gradient decay at the borders of the neoplasm. Conclusion: The variability of radiation therapy methods ensures the most acceptable coverage that keeps the dose load within international standards’ ranges. Mastering these methods will improve the effectiveness of radiation therapy for various cancer cases

Comparison of dosimetry parameters of three-dimensional conformational radiation therapy and volumetric modulated arc therapy on the example of treatment of a patient with salivary gland adenocarcinoma

Relevance: An optimal choice of radiation therapy method is the main prerequisite for successful completion of treatment. Continuous analysis of radiation therapy methods’ advantages and comparing their parameters and dose load in typical cases will serve to increase the treatment efficacy and reduce the unavoidable load on critical organs. Purpose: To check the plans of treatment by volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiation therapy (3D-CRT) methods, make their comparison, and identify the advantages using an example of a treatment design for a patient treated at the Daily Radiotherapy Hospital of the Kazakh Institute of Oncology and Radiology (Almaty, Kazakhstan). Results: The presented illustrations of the process planning and the numerical analysis of the dose load on critical organs show VMAT advantages for radiation therapy of salivary gland cancer: optimal coverage, sparing load on critical organs and healthy tissues, gradient decay at the borders of the neoplasm. Conclusion: The variability of radiation therapy methods ensures the most acceptable coverage that keeps the dose load within international standards’ ranges. Mastering these methods will improve the effectiveness of radiation therapy for various cancer cases.

COMPARISON OF DIAGNOSTIC AND RADIOTHERAPY PLANNING PROTOCOLS IN LUNG CANCER TREATMENT

Purpose: The purpose of the study was to compare a standard diagnostic protocol for computed tomography imaging on a positron emission tomography scanner at the Department of Nuclear Medicine, and a radiotherapy imaging protocol for pre-planning needs in radiotherapy for lung cancer treatment, to determine the differences between these two protocols and to propose possible improvements in the dose optimisation for computed tomography imaging in a radiotherapy protocol. Methods: In this retrospective study, data were collected via the SyngoVia program and statistically analysed according to the patient dose load in computed tomography imaging in standard and radiotherapy protocols. The analysis encompassed data on a total of 56 patients in the period from 1 January 2017 to 1 December 2018. We compared data on patient dose load in computed tomography imaging in a standard protocol before and after the introduction of the improved sinogram-affirmed iterative reconstruction method (SAFIRE). Results and discussion: It was established that there are statistically significant differences in dose per patient (p<) in computed tomography imaging in standard and radiotherapy protocols. Statistically significant differences were also established in computed tomography imaging in the standard protocol before and after the introduction of the improved iterative reconstruction method (p=0,001). Dose load on the lung in computed tomography imaging was 67.5% lower in the standard protocol with the iterative reconstruction in image space (IRIS) method than in the radiotherapy protocol. The introduction of the improved SAFIRE method additionally lowered the dose per patient by 34.2% compared to the IRIS method. Conclusion: In the future, the introduction of the improved iterative reconstruction method is possible for the reconstruction of tomographic images, including for radiotherapy imaging protocol that takes into account the impact of the indirect reduction in the dose on the accuracy of the identification of tumour target volumes when planning radiation treatment for the patient. Key words: positron emission tomography with computed tomography, iterative reconstruction, dose optimization, lung cancer, radiation treatment planning