A detector assembly for a CT imaging system, said detector assembly comprising: a scintillator block comprising a plurality of pixels, each pixel configured to receive x-ray beams travelling in a transmission direction; a plurality of photodiodes; and a light guide coupled between said scintillator block and said plurality of photodiodes, said light guide comprising a plurality of light pipes, each light pipe being configured to guide light emitted from a pixel of said plurality of pixels into an associated photodiode of said plurality of photodiodes, wherein each pixel has a first cross-sectional area that is substantially perpendicular to the transmission direction, wherein each photodiode has a second cross-sectional area that is substantially perpendicular to the transmission direction, wherein the first cross-sectional area is different from the second cross-sectional area, wherein each light pipe extends from a first end of said light guide to a second end of said light guide, wherein at said first end, each light pipe has a first end cross-sectional area that is substantially equal to the first cross-sectional area of each pixel, wherein, at said second end, each light pipe has a second end cross-sectional area that is substantially equal to the second cross-sectional area of each photodiode, and wherein the plurality of photodiodes are spaced apart from one another such that, for each light pipe, the first end cross-sectional area is substantially centered with the second end cross-sectional area along the transmission direction, characterized in that each light pipe is made of an x-ray detecting material. a scintillator block comprising a plurality of pixels, each pixel configured to receive x-ray beams travelling in a transmission direction; a plurality of photodiodes; and a light guide coupled between said scintillator block and said plurality of photodiodes, said light guide comprising a plurality of light pipes, each light pipe being configured to guide light emitted from a pixel of said plurality of pixels into an associated photodiode of said plurality of photodiodes, wherein each pixel has a first cross-sectional area that is substantially perpendicular to the transmission direction, wherein each photodiode has a second cross-sectional area that is substantially perpendicular to the transmission direction, wherein the first cross-sectional area is different from the second cross-sectional area, wherein each light pipe extends from a first end of said light guide to a second end of said light guide, wherein at said first end, each light pipe has a first end cross-sectional area that is substantially equal to the first cross-sectional area of each pixel, wherein, at said second end, each light pipe has a second end cross-sectional area that is substantially equal to the second cross-sectional area of each photodiode, and wherein the plurality of photodiodes are spaced apart from one another such that, for each light pipe, the first end cross-sectional area is substantially centered with the second end cross-sectional area along the transmission direction, characterized in that each light pipe is made of an x-ray detecting material.