An apparatus includes an x-ray source (112) that generates transmission radiation that traverses an examination region (108) and a detector (116) that includes a photo-converter (204) that detects the radiation and generates a signal indicative thereof. The photo-converter (204) includes a light receiving region (260) on a back side (264).5The light receiving region receives light indicative of the detected radiation. The photo-converter (204) further includes read-out electronics (240) within a front side (228), which is located opposite the back side (264). The read-out electronics (240) process a photo-current indicative of the received light to generate the signal indicative of the detected radiation. The photo-converter (204) further includes a photodiode (208, 212, 232) 10disposed between the light receiving region (260) and the read-out electronics (240). The photodiode (212) produces the photo-current. A reconstructor (128) reconstructs the signal to generate image data indicative of the examination region (108).