A method for real-time target reconstruction from target image projections including dividing an object into external and internal sub-objects, acquiring external sub-object data, acquiring internal projections, each internal projection including an internal-internal projection which is the projection of the internal sub-object only as if the external sub-object is null, and an internal-external projection which is the projection of the external sub-object only as if the internal sub-object is null, using the external sub-object data to estimate internal-external projections, subtracting the estimated internal-external projections from the acquired internal projections to obtain internal-internal projections, and reconstructing the internal sub-object from the internal-internal projections.