A cone beam computer tomography, CBCT, system , comprising at least one X-ray source , a flat panel detector, FPD, and one or more devices providing data collection, computation and/or storage functionality, wherein the FPD comprises: a CMOS readout wafer , comprising a region configured to function as drift region , made from highly resistivity silicon of a first conductivity type with a resistivity of 500 Ohm cm - 20 kΩcm, and further comprising: implanted charge collectors each one being associated with a pixel of size L, being defined by the spacing of the charge collection implants , on a front side ; readout electronics on the front side, part of which is contained in every pixel of size L; an absorber (18, 50, 218, 218', 218", 218′′′, 318, 418, 518) made from a material of a second conductivity type opposite to that of the first conductivity type; an entire back side of the CMOS readout wafer and the absorber comprising an atomically flat particle and oxide free covalent direct wafer bond; a metallized back contact on the absorber on the side opposite to the CMOS readout wafer; wherein the FPD is configured to allow electric charges generated by X-ray incident in the absorber to drift along electric field lines of the absorber and the drift region of the CMOS readout wafer to be collected by the implanted charge collectors when the FPD is in operation; and wherein the FPD is configured so that electrical signals induced by the charges are amplified, shaped and transformed into digital signals in the readout electronics to be received by the devices with data collection, computation and storage functionality and to generate computed tomography images on at least one computer screen. a CMOS readout wafer , comprising a region configured to function as drift region , made from highly resistivity silicon of a first conductivity type with a resistivity of 500 Ohm cm - 20 kΩcm, and further comprising: implanted charge collectors each one being associated with a pixel of size L, being defined by the spacing of the charge collection implants , on a front side ; readout electronics on the front side, part of which is contained in every pixel of size L; an absorber (18, 50, 218, 218', 218", 218′′′, 318, 418, 518) made from a material of a second conductivity type opposite to that of the first conductivity type; an entire back side of the CMOS readout wafer and the absorber comprising an atomically flat particle and oxide free covalent direct wafer bond; a metallized back contact on the absorber on the side opposite to the CMOS readout wafer; wherein the FPD is configured to allow electric charges generated by X-ray incident in the absorber to drift along electric field lines of the absorber and the drift region of the CMOS readout wafer to be collected by the implanted charge collectors when the FPD is in operation; and wherein the FPD is configured so that electrical signals induced by the charges are amplified, shaped and transformed into digital signals in the readout electronics to be received by the devices with data collection, computation and storage functionality and to generate computed tomography images on at least one computer screen. <EOS>