engineering volume 47 2008 issue 1 violates equation 1 4 more strongly and the corresponding reconstructions become increasingly worse as confirmed by the following quote from the paper u201c a short kernel incurs a large error as revealed in fig2 b u201d conceptually the main difference between the approach in z chen local volume reconstruction from width truncated cone beam projections by convolution backprojection optical engineering volume 47 2008 issue 1 and the approach in the present invention is that the former attempts to make reconstruction from truncated data as close to conventional reconstruction as possible which in particular necessitates the use of data extrapolation in the present invention the goal is to come up with an image that only looks qualitatively similar to conventional reconstruction in particular the algorithm of the present invention can be used with non truncated data as well the main steps for running the algorithm in detail are in steps 10 40 fig1 is a flow chart of the steps for reconstruction using variable length tomography step 10 load the current cb cone beam projection d f s u v into computer memory suppose that this cb projection corresponds to the source position y s k the detector surface corresponding to the x ray source located at y s k is denoted dp s k step 20 filtering for each detector row convolve the data with a filter let i r be the index of a detector row i c be the index of a detector column and let.