Forward projection apparatus

A forward projection apparatus for performing a forward projection through an image, the forward projection apparatus comprising:

• a ray providing unit for providing rays traversing the image, the rays being fictive rays arranged along straight lines emanating from a fictive radiation source,
• an interpolation unit for determining interpolated values located on the provided rays, wherein the interpolation unit is adapted to apply an interpolation kernel to a plurality of image elements of the image for determining the interpolated values,
• a summation unit for summing the interpolated values located on a respective ray for determining a projection value for the respective ray,
• wherein at least one of the number of provided rays, a ray spacing between the provided rays and a kernel width of the interpolation kernel is varied depending on the ray width relative to an effective image element spacing between the image elements of the image, wherein the image elements are arranged in a grid and wherein the effective image element spacing for a ray is defined as a projection of an image element spacing parallel to a main axis of the grid onto a line being perpendicular to the ray.