Nosyk O. Optimization of the patients’ medical exposure in projectional X-ray diagnostic

SUMMARY Nosyk Olgа. Optimization of the patients’ medical exposure in projectional X-ray diagnostic. – Manuscript. The thesis is submitted for a philosophy doctor degree in biological sciences; specialty: 03.00.01 - Radiobiology. - State institution "Grigorev Institute for medical radiology and oncology of the National Academy of Medical Sciences of Ukraine", Kharkiv, 2021. –State institution "National Scientific Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine", Kyiv, 2021 The thesis is devoted to the issues of optimization the patients’ radiation protection system and the possibility of radiation risks reducing for additional cases oncological diseases for the Ukrainian population from examinations in projection X - ray diagnostics. The analysis of X-ray examinations, the park of X-ray equipment in Ukraine and the for exposure parameters X-ray diagnostic examinations (techniques) based on the results of the X-ray diagnostic departments survey is performed. According to the patients’ doses investigation the national diagnostic reference levels for 10 radiography types, 3 fluoroscopy types and for mammography are established. It is shown that establishment / reviews the diagnostic reference levels in Ukraine it is possible using an indirect method of the patients’ radiation doses estimating. To the study of equivalent and effective patients’ doses the 116 phantom simulations of patients' irradiation conditions were performed using anthropomorphic heterogeneous adult phantom for 8 types of X-ray examinations and fluorography on X-ray analog and digital devices. The conversion factors from dosimetric values which are controlled in practice, to the values of equivalent and effective doses are determined. According to the investigation results the absolute expected risk for cancer additional due to X-ray diagnostic exams in projection radiology is 2323 cases per year. The main contribution is formed by film fluorography - 1495 cases, while digital fluorography is included only 339 cases. The total attributive cancer risk from all types of projection X-ray procedures is 1.5 %, of which 0.95% is added by film fluorography. Thus, the study of patient doses and the implementation in practice of the national diagnostic reference levels concept allows substantiating X-ray diagnostic studies and identifying ways to the radiation safety optimization in medical diagnostic exposure. That will be help to reduce as the individual patients doses as the collective effective doses and radiation cancer risks for the Ukrainian population while maintaining the required diagnostic quality of X-ray examinations. Key words: X-ray diagnostics, patients’ exposure doses, diagnostic reference levels, optimization, equivalent doses, effective doses, radiation risks.