1. A computer-implemented method, the method comprising: providing an edge-detected data set of voxels that represents a surface boundary of a three-dimensional generally tubular structure according to a three-dimensional voxel data set for the tubular structure; computing a gradient vector field of a distance transformation for the edge-detected data set; and identifying a voxel data set corresponding to a centerline of the tubular structure according to a derivative of the gradient vector field.