An X-ray image acquisition apparatus (15) includes a conversion panel (20) aligned with a photo detector array (40). The conversion panel (20) includes a plurality of conversion cells (22), each including a conversion body (31), an X-ray transparent and light reflective file over the top (32) of the body (31), and a light reflective film (36) surrounding the body (31). The body (31) is made of a scintillating material that efficiently generates optical light photons in response to X-ray radiation illuminating thereon and is substantially transparent to the optical light photons. The body (31) is also sufficiently long to absorb the X-ray radiation over a wide range of energy levels. The light reflective films (36, 38) collimate the optical light photons generated in the body (31) toward the photo detector array (40) to form X-ray images.