Parameter Calibration in Imaging of CT System

Abstract

CT can perform tomography imaging of biological tissue and engineering materials without the destruction of the sample, using the absorption characteristics of the sample to the ray energy, thus obtaining the structural information of the sample. In the background of CT system, four questions are proposed. According to our subject to geometric data, images and other conditions to obtain the CT system, the distance between the center of rotation of the detector unit, the rotation of the 180 directions, and through the CT system parameters to solve information related to two different groups of images of unknown material. For the problem, to find the parameters of CT system, firstly, we combine Annex 2 the distance between the ellipse and the circle and the distance between the image circle trajectory and given geometric data to obtain the distance between the detector units (d). The calculation result of d is 0.2762mm. Secondly, we find the maximum absorption point is in column EU and the widest range of absorption is in column BI. With the data above, the Cartesian coordinate system is established with the center of the ellipse as the origin, and the coordinates of the rotation center are obtained as (-9.2527,5.9468). We then separate the ellipse images in the Appendix 2 and the round images by weighted calculation. 180 directions are sorted out with the changing of the image of the absorption rate of the ellipse. The image range is from 120.2381 degrees to 299.2284 degrees through multiple iterations. Data in 180 specific directions will be detailed in the text. Finally, to make the result more accurate, we optimized the model further. Through multiple iterations, d is 0.2772mm and the central coordinate of rotation is (-9.2862, 5.9598). Known: geometric values of a homogeneous solid medium placed on a square tray; the absorption intensity of each point in the Annex 1 given in the title; acceptance information in Annex 2. By establishing the corresponding mathematical model, the position of the rotation center of the CT system in the square tray, the distance between the detector units and the 180 directions of the X ray used by the CT system are determined.