Tomographic reconstruction [1] is a method of imaging by illuminating the object in many different directions in the plane of interest, using X-rays or ultrasound. An image is formed from changes in a physical variable occurring in the planar cross section. Typically, changes in propagation delay or arrival time are used to reconstruct an image of the slowness variations (where slowness is the inverse of velocity), or changes in signal amplitude are used to produce an attenuation image.