Malakhova M. Models and methods for determining the parameters, diagnostics and debugging of the computerized X-ray management system

The thesis is devoted to the development of a mathematical model, methods and software for defining parameters, diagnostics and debugging of a computerized X-ray control system. The purpose of the thesis is to increase the quality of X-ray diagnostics by means of increasing the accuracy of determining the parameters of a computerized X-ray control system. The main methods of the dose load reducing during X-ray diagnostic procedures have been considered in the dissertation. It is determined that one of the perspective directions of solution of this problem is to increase the accuracy of determination of dosimetric parameters, diagnostics and debugging of control systems by X-ray diagnostic complexes. The existing methods of emission characteristics formation of X-ray emitter for computerized control systems by X-ray installation have been analyzed. The method of individualization of generalized emission characteristics of X-ray emitter of a computerized X-ray control system has been proposed for the first time. The suggested method differs from the existing ones by being based on the mathematical deformation of the coordinate plane according to the empirical data. It allows to increase the accuracy of the individual emission characteristics determination of the X-ray emitter in the whole range of values of the anode voltage up to 6.5 times. The value of the error of anode current setpoint can be reduced by 8.5%, in comparison to the previously used methods based on the approximation of experimental data. This can be achieved by means of the preservation of shape and position of the family of curves. Moreover, the method usage allows to reduce of calibration time in comparison to direct detailed emission characteristics measurement. The accuracy of calibration result fully matches to requirements of the cutting edge standarts. The mathematical model for measuring individual emission characteristics of an X-ray computerized X-ray control system has been improved by the development of model equation. It allowed to use the estimation of uncertainty as a criteria for selecting a subset of empirical points for calculation. The accuracy of obtained results has been increased. The application of this strategy ensures that the deviation of the X-ray tubes anode current from the set value does not exceed 1.5% at the initial region of exposure (before the activation of the system of current automatic stabilization) in the range of anode current from 25 to 250 mA for the incandescence current from 4 to 6 A. The incandescence current uncertainty estimation is from 0.035 to 0.052 A. Whereas for an arbitrary choice of a subset of empirical data for the calculation of anode current deviation on the initial section reached 5% and the value of uncertainty estimation for heating current fluctuated from 0,118А to 0,18А. The accuracy estimation has been carried out according to international requirements to metrological measurements especially concept of measurement uncertainty. This is in a good agreement with the concept of uncertainty of measurement introduction into the metrological practice of Ukraine. It allows to use the developed algorithm for defining parameters, diagnostics and debugging of a computerized X-ray control systems widely. The method for determining the parameters, diagnostics and debugging of the computerized X-ray control system has been improved by creating a mechanism for simultaneous interaction of several programs with the system. It allows to reduce the systems’ diagnostic and debugging time from 2 to 4 times, depending on the complexity of technical malfunction when servicing the power supply devices of medical X-ray machines, and, as a result, to reduce the cost of these works performing in the range from 4% to 35%. The results of the study became a scientific and methodological basis for the practical creation of software tools for determining parameters, monitoring their compliance with the established values, diagnosis and debugging of modern computerized control systems of X-ray installations. These tools usage is required for the X-ray diagnostics quality increasing by means of accuracy increasing of medical research and reducing of dose load for the population as well as X-ray equipment lifetime prolongation. The developed package of service programs "IEC FxTools v2.0" has been implemented for many enterprises in order to optimize the processes of determining parameters, diagnostics and debugging of the computerized control systems for medical diagnostic X-ray machines power supplies. It has been operated for several years, that is confirmed by the acts of implementation. Keywords: mathematical model of measurement, emission characteristics, X-ray radiator calibration, equipment diagnostics, computerized control system, debugging software.