  English: This paper concerns the image reconstruction from a few projections
in Computed Tomography (CT). The main objective of this paper is to show that
the problem is so ill posed that no classical method, such as analytical
methods based on inverse Radon transform, nor the algebraic methods such as
Least squares (LS) or regularization theory can give satisfactory result. As an
example, we consider in detail the case of image reconstruction from two
horizontal and vertical projections. We then show how a particular composite
Markov modeling and the Bayesian estimation framework can possibly propose
satisfactory solutions to the problem. For demonstration and educational
purpose a set of Matlab programs are given for a live presentation of the
results.
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  French: Ce travail, \`a but p\'edagogique, pr\'esente le probl\`eme inverse
de la reconstruction d'image en tomographie X lorsque le nombre des projections
est tr\`es limit\'e. voir le texte en Anglais et en Fran\c{c}ais.
