## 1 Introduction  
Problems related to the influence of artifacts on the quality of evaluation of the internal structure of test objects (TOs) in X-ray computed tomography (CT) continue to be one of the most important areas of research in tomography [1; 2; 3; 4; 5]. This is primarily due to the expansion of the range of objects that have not previously been tested using the X-ray CT method. Moreover, the noted expansion occurs not only along the line of complication of the structure of the test objects, but also an increase in their size, an increase in the density and effective atomic number of the materials of their structural fragments. All of the above leads to a decrease in the transparency of the test objects for X-ray radiation and, consequently, an increase in the influence of metal artifacts on the quality of testing objects by X-ray CT [6; 7; 8]. Therefore, the role of studies related to the reduction of the contribution of metal artifacts to the bias in estimates of the distributions of informative parameters over the TO slice (volume) increases [8; 9; 10; 11]. Here, informative parameters are the Hounsfield number, linear attenuation coefficient (LAC) of radiation, density, and effective atomic number. In connection with the transition of the X-ray CT method from a means of visualizing the TO internal structure to a measuring tool, which has been outlined in recent decades [12; 13], the density and effective atomic number can be considered the prevailing informative parameters. It was noted in [14] that the design of X-ray CT systems is based on the principles of physical and technical feasibility. In relation to X-ray CT, the principle of physical feasibility is understood as the presence of physical laws that connect the set of measured projections (sinograms) with the distribution of density (density and effective atomic number) over the TO slice (volume) using mathematical relationships. Moreover, this relationship should be one-to-one. It was noted in [15] that the physical reasons include the differences between the actual laws of emission, interaction, and registration of photon radiation from some idealized laws and models, for example, the model of a plane-parallel beam of mono-energetic radiation. The principle of technical feasibility indicates the availability of technical capabilities for the implementation of the physical principle in order to obtain estimates of the distributions of the required informative parameters over the TO slices or its entire volume with the calculation time and accuracy specified by the consumer. Accordingly, it is possible to divide, with a certain degree of conditionality, the entire set of reasons causing the appearance of artifacts in the X-ray CT into physical and technical factors. The purpose of the proposed study is to clarify the nature of metal artifacts in computed tomography and to substantiate, by simulation modeling, the possibility of correcting metal artifacts in the final images of CT using a rational choice (optimization) of the technical parameters of the analyzed systems. It is necessary to solve several problems to achieve the above goal: to develop a mathematical model for evaluating metal artifacts in X-ray computed tomography in relation to the control of objects with fragments of low radiation transparency; to carry out a cycle of computational experiments to study symmetric and asymmetric objects with low and high-density inclusions and with inclusions from materials with high atomic numbers using the X-ray CT method; to identify the influence of which main technical (physical) factors on the level of metal artifacts is the most significant; to illustrate the possibility of reducing metal artifacts by a rational choice of significant parameters. Here, radiation transparency is understood as the transparency of objects to X-rays [6; 7]. Let us make a number of necessary explanations concerning the stated goal of research and the tasks for its implementation.