Direct extraction of boundaries from computed tomography scans

This paper presents a method, based on the Filtered Backprojection technique (FBP), to extract directly the boundaries of X-ray images, without previous image reconstruction. The authors preprocess the raw data in order to compute directly the reconstructed values of the gradient or of the Laplacian at any location in the plane (defined with real coordinates). The reconstructed value of the gradient and of the Laplacian correspond to the exact mathematical definition of the differentials of the image. For noisy data, the authors propose also to use an extension of existing FBP techniques, adapted to the computation of the gradient and of the Laplacian. Finally, the authors show how to use the corresponding operators to perform the segmentation of a slice, without image reconstruction. Images of the reconstructed gradient, Laplacian, and segmented objects are presented