A Practical Geometric Calibration Method of Cone-Beam CT System Using Simple Handmade Phantom

作者：Wu, S Y; Li, H W; Qi, H L; Luo, Y B; Zhen, X; Xu, Y; Zhou, L H^*

来源：Journal of Medical Imaging and Health Informatics, 2015, 5(8): 1915-1920.

DOI：10.1166/jmihi.2015.1669

• Geometry Calibration
• Cone-Beam CT
• Image Reconstruction
• Image Blurring
• Sharpness Function

Cone-beam computed tomography (CBCT) is one of the most widely used image guidance tools in image guided radiation therapy (IGRT) and dental radiology. Geometric calibration involves the estimation of a set of parameters that fully describe the geometry of the system, and is essential for accurate image reconstruction. A practical geometric calibration method has been developed with simple handmade phantom for the prototype dental cone-beam CT system. In the proposed method, a simple phantom was made with easily accessible materials. The initial estimation was achieved by the fast analytic method. In order to compensate for the error resulting from image segmentation and the unrealistic hypothesis of the analytic algorithm, one iterative algorithm was proposed to find the optimal parameters around the initial estimation. Based on the finding that the error at the analytic step makes reconstructed image blurred, one sharpness function was utilized as the metric to evaluate the gradient of the reconstructed image as the cost function at the iterative step. The result indicates that our method is robust and accurate. Comparing with the current analytic method, the proposed method reduces the relative error of the horizontal coordinate of projection center in the detector from 2.42% to 0.23%, and the error of roll angle of the detector from 0.83% to 0.53%. The image reconstruction after geometry calibration on the realistic CBCT system also validates the efficiency and efficacy of the proposed method.

• 出版日期2015-12
• 单位南方医科大学