1. A method for reconstructing an image from cone beam (CB) projection data provided by at least one detector, comprising the steps of: a. scanning an object to collect cone-beam projection data; b. loading the CB (cone beam) projection data into a computer; c. using the CB projection data for reconstructing an image of the object; and d. repeat loading and using additional CB projection data until image reconstruction is finished at all reconstruction points x, wherein during step c only truncated CB data are used at one or more reconstruction points x inside the object, wherein the said truncated CB data are defined as data which are insufficient for theoretically exact reconstruction at a point x; wherein the step c. of reconstructing includes the substeps of: c.i. filtering the truncated CB data; and c.ii. back-projection updating of the image being reconstructed; wherein the substep c.i. uses a filter of a length longer than the length of a filter associated with computing a derivative, but shorter than the length of a filter associated with theoretically exact reconstruction (of infinite length or of length equal to a support of the object along the line of filtration); wherein the image reconstructed in step d is not intended to approximate a theoretically exact reconstruction, but allows differentiation of tissue types that comprise the object being scanned, and wherein the computer does not process the projection data for the image reconstruction using iterative steps, does not perform filling in of the missing data, and does not use wavelets and curvelets.