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DR/CR detector artefacts & correction

Schematic panels of detector-related artefacts. DR flat-panel: irregular shading from non-uniform absorption-layer sensitivity, fixed by flat-field (gain) correction (not pixel correction); defective pixels from failed TFT or photodiode, fixed by bad-pixel mapping and interpolation (not gain correction). Computed radiography: residual ghost image from incomplete plate erasure (not underexposure); grid-line moire from a stationary grid aliased by reader sampling; laser-readout banding from non-uniform laser scan. A caption notes that all correction is computational and applied after exposure, so acquisition or plate faults need a repeat exposure rather than post-processing.

Digital detector artefacts: appearance, cause and correction Schematic panels of detector-related artefacts. DR flat-panel: irregular shading from non-uniform absorption-layer sensitivity, fixed by flat-field (gain) correction (not pixel correction); defective pixels from failed TFT or photodiode, fixed by bad-pixel mapping and interpolation (not gain correction). Computed radiography: residual ghost image from incomplete plate erasure (not underexposure); grid-line moire from a stationary grid aliased by reader sampling; laser-readout banding from non-uniform laser scan. A caption notes that all correction is computational and applied after exposure, so acquisition or plate faults need a repeat exposure rather than post-processing. Detector artefacts: appearance, cause, and how each is (or is not) corrected DR flat-panel detector — hardware faults, corrected after exposure Irregular shading cause: uneven absorption/conversion layer sensitivity → broad, low-frequency fix: flat-field (gain) correction pixel correction cannot remove it Defective pixel(s) cause: failed TFT switch or photodiode → dead (dark) or hot (bright) spot, fixed fix: bad-pixel map + interpolation gain correction cannot fix it Computed radiography — plate and readout artefacts Residual (ghost) image cause: incomplete plate erasure / high prior dose not from underexposure Grid-line / moiré cause: stationary grid aliased by CR sampling moving Bucky grid blurs it Laser-readout banding cause: non-uniform laser scan / stimulation efficiency → banding & line artefacts Correction is computational: offset, gain (flat-field) and bad-pixel maps are applied after exposure — acquisition records the raw detector non-uniformities, so artefacts are not removed at the moment of exposure. CR processing errors (histogram / LUT, frequency filtering) can also cause artefacts. Acquisition and plate faults — motion, grid moiré, ghosting — need a repeat exposure, not post-processing.
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