METHODS FOR PREPROCESSING TOMOGRAPHIC IMAGES TAKING INTO ACCOUNT THE THERMAL INSTABILITY OF THE X-RAY TUBE
A. S. Ingacheva1,2, A. B. Buzmakov2
1Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Bol'shoi Karetnyi per. 19, Moscow, 127051, Russia
2Shubnikov Institute of Crystallography, Crystallography and Photonics Federal Scientific Research Center , Russian Academy of Sciences, Leninskii prosp. 59, Moscow, 119333 Russia
Keywords: компьютерная томография, артефакты, ужесточение пучка, инвариантность преобразования Радона, дрейф центра пучка рентгеновского излучения, computed tomography, artifacts, beam hardening, invariance of the Radon transform, drift of the center of the X-ray beam
Abstract
For correct numerical interpretation of the results of tomographic experiment, i.e. estimates of objects attenuation coefficients 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 of the set-up geometrical parameters during the experiment. We have analyzed two possible types of data corruptions during experiment and suggested corrections for them. The first correction is applied to change thermal shifts regarding beam decentralization, and the second accounts for and eliminates the effect of the polychromatic nature of the 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 automatic parameter adjustment and experts is about 90%.
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