A system and method for forming volumetric images of an imaged object based on multiple radiation measurements of the object taken from different angles. A first volumetric image of the object may be calculated using a direct reconstruction method from a plurality of radiation measurements of the object. At least one iteration of an iterative reconstruction method may be performed to compute a second volumetric image of the object. The iterative reconstruction method may be initialized with the first volumetric image of the object.