An explanation of the effects of Squashing in limited angle tomography.

The effects of Squashing, an algorithm introduced by J.A. Reeds and L.A. Shepp (see ibid., vol.MI-6, no.2, p.89-97, June 1987), are described. It is proven that Squashing induces a weight function upon the projections. Intuitive and numerical evidence is presented showing that this weight function is not desirable at limited angles. A method to counteract the effects of the weight function and extend the usefulness of the algorithm to 120 degrees is proposed.