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. <EOS>