A new method is presented for automatic contour extraction in computerized tomography (CT) reconstruction, based on projection segmentation and backprojection. Contour extraction is of great importance in medical applications, especially in nondestructive inspection. Manual segmentation includes pixel selection, geometrical boundary selection, and tracing, however, it depends on the experience of the operators and is time-consuming. Most fully automatic segmentation methods for CT images are usually impractical
due to the obvious noise in reconstructed slices. Because the backprojection algorithm is of a high-pass nature, the noise is always in high frequencies. The projections, however, are much clearer than the reconstructed slices. The advantage of the new algorithm is its simplicity in segmenting the projections instead of the slices. Simulation results illustrate the accuracy of this method. A circular trajectory cone-beam micro-CT system is used to validate the algorithm. The experiment result shows a perfect 3-D contour of a rat skull.