Integrated intersection area (orange). It is the intersection area of a Cartesian pixel (black) with a segment of a circle (blue) and it is assigned to a polar pixel (hatched region) that is defined by an inner radius r_inner, an outer radius r_outer, a left border ϕ_l and a right border ϕ_r. The overlayed polar grid is shown in gray and the two radial and angular borders of a selected polar pixel are highlighted in dark gray.