Reconstructing plane sets from projections

We give some uniqueness results for the problem of determining a finite set in the plane knowing its projections alongm directions. We apply the results to the problem of the reconstruction of a homogeneous convex body with a finite set of spherical disjoint holes. Ifm X-ray pictures with directions in some plane are given, then the problem is well posed provided the number of the holes is less than or equal tom and the set of the directions satisfies a suitable condition.