| Abstract [eng] |
Unjustified exposure to ionizing radiation can have a bad influence to life quality and impair status of health. The main influence to annual radiation dose is made by X-ray diagnostic procedures (29 % share of total yearly ionizing radiation dose) and indoor decay products of radon (31 % share of total yearly ionizing radiation) [1]. In comparison with year 2012, ionizing radiation from medical X-ray diagnostic procedures increased by 28 % per year. This master degree final project involves an overview of X-ray diagnostic situation in Lithuania, quality assurance techniques in X-ray diagnostic, quality assurance devices for X-ray diagnostic equipment. One of most important task of quality assurance in X-ray diagnostics, is to determine entrance surface dose of the patient. Calculation according to three methodologies of entrance surface dose was done. Results between techniques were compared with each other. Methodologies analysed in this project are: 1) Air kerma free-in-air dependence on tube voltage method; 2) Dose area product method; 3) Solid state dosimeter method. For air kerma (free-in-air) dependence on tube voltage method, semiconductor silicon detector - UNFORS Multi-O-Meter was used. For dose area product method, integrated in X-ray machine dose area product meter DAP-M4 was used. For solid state method, optically stimulated luminescence and thermally stimulated luminescence dosimeters were used. It was find out, what after measuring and comparing results with each other, thermally stimulated luminescence dosimeters had to low sensitivity, so the main entrance surface dose evaluation from solid state dosimeter method point of view, was carried out using optically stimulated luminescence dosimeters. After comparing results from all methodologies, it was found out that the entrance surface dose calculations based on air kerma free-in-air dependence on tube voltage method gives 24% - 32% lower values in compare with values measured using solid state dosimetry method. Dose area product method was only relatively compared with other methods. And it gives best compliance with solid state dosimetry method, which is a “gold standard” in X-ray diagnostics for measuring entrance surface dose. |
