Methods of Preprocessing Tomographic Images Taking into Account the Thermal Instability of the X-ray Tube

Abstract

For correct numerical interpretation of tomographic images, i.e., estimates of the attenuation coefficients of objects, it is important to obtain reconstruction of high quality, which depends directly on the methods of processing experimental data. Data processing flow begins with its preparation for the application of the reconstruction algorithm. The necessary part of data processing contains the subtraction of the black field, normalization considering empty data, and taking logarithm. This part is not sufficient for obtaining high-quality reconstruction when working with real data since it is not ideal. Real data include noise and distortions due to changes in the setup geometrical parameters during the experiment. We have analyzed two possible types of data distortions during experiment and suggested corrections for them. The first one corrects thermal shifts regarding beam decentralization, and the second eliminates the effect of the polychromatic nature of X-ray radiation on the results of tomographic reconstruction. These methods were tested with both real and synthetic data. Both synthetic and real experiments show that suggested methods improve the reconstruction quality. In real experiments, the level of agreement between the automatic parameter adjustment and experts is about 90%.