1. A method for iteratively reconstructing an image of an object, the method comprising: accessing measurement data associated with the image, the measurement data obtained from a detector array; and using, with a computer operably coupled to the detector array, a simultaneous algorithm to reconstruct the image, wherein using the simultaneous algorithm to reconstruct the image comprises: determining, with the computer, a scaling factor that is voxel-dependent; and applying, with the computer, the voxel-dependent scaling factor to a gradient of an objective function to reconstruct the image.