Ghosts in tomography : the null space of the radon transform

Abstract

Let w o, …,wp-1 E S 1 be p distinct directions and let R denote the RADON transform. The functions f with support in the unit disc and with Rf(s, wj) = 0 for sE [-1,1] and j = 0, ... , p-1 are given. "Ghosts'; are constructed, i. e. functions in the null space that pretend not existent tumors. Methods to avoid such ghosts are indicated.