in some embodiments , an optical mask for a ct detector is disclosed . in some embodiments , the mask is intercalated between a photodiode array and a scintillator array forming the ct detector . in some embodiments , the optical mask may extend along one or more axes and differentially absorbs and / or reflects light emitted from the scintillators at edges of photodiodes forming the diode array , with less absorption or reflection at edges of tiled die forming the diode array than in central portions of each of the die . through selective absorption and / or reflection , transference of light photons from a scintillator to the photodiode corresponding to a neighboring scintillator is spatially modified , at least partially compensating for spatial differences in crosstalk signals between adjacent pairs of photodiode / scintillator cell elements . this reduction in differential crosstalk reduces artifacts in a reconstructing data descriptive of internal portions of a subject , which improves diagnostic value of the data .