title: Spatial resolution properties of penalized-likelihood image reconstruction: space-invariant tomographs.
abstract: This paper examines the spatial resolution properties of penalized-likelihood image reconstruction methods by analyzing the local impulse response. The analysis shows that standard regularization penalties induce space-variant local impulse response functions, even for space-invariant tomographic systems. Paradoxically, for emission image reconstruction, the local resolution is generally poorest in high-count regions. We show that the linearized local impulse response induced by quadratic roughness penalties depends on the object only through its projections. This analysis leads naturally to a modified regularization penalty that yields reconstructed images with nearly uniform resolution. The modified penalty also provides a very practical method for choosing the regularization parameter to obtain a specified resolution in images reconstructed by penalized-likelihood methods.
authors.affiliation: Michigan Univ., Ann Arbor, MI.
authors.forename: J A
authors.initials: JA
authors.lastname: Fessler
authors.forename: W L
authors.initials: WL
authors.lastname: Rogers