An X-ray beam transmitted through an object is transmitted through a grid, which has been moved to the X-ray irradiation position, and reaches a panel sensor after scattered X-rays are removed by the grid. The antireflective composition comprises a polymer of formula I,wherein 1\u2266x\u22662; 1\u2266y\u22665; 1\u22670; m>0; n>0; R is a chromophore, M is a metal selected from Group IIIB to Group VIB, lanthanides, Group IIIA, Group IVA except silicon; and L is an optional ligand. The apparatus may further comprise a circumferential collection gap that collects liquid from the gas exchange medium and directs it toward the first outlet.