Appendix for Digital Image Acquisition and Display
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| Amorphous silicon (a-Si) | show 🗑
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| show | Amorphous selenium layers have the same structure as single crystals over short distance, but are less ordered over larger distances. As a result, amorphous selenium layers provide uniform x-ray detection over the large areas needed by flat-panel x-ray de
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| Automatic rescaling (Auto ranging, rescaling, scaling, normalization) | show 🗑
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| Bit depth | show 🗑
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| Complimentary metal-oxide semi-conductor (CMOS) | show 🗑
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| show | the smallest exposure change (signal difference) that can be captured by a detector. Ultimately, contrast resolution is limited by the dynamic range and the quantization (number of bits per pixel) of the detector. Increased contrast resolution is consider
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| detective quantum efficiency (DQE) | show 🗑
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| show | the detector size and FOV describe the useful image acquisition area of an imaging device. Cassette-less digital systems have a fixed OV which makes some projections difficult, while cassette-based CR systems have flexible FOVs like screen/film.
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| show | the detector element is the smallest resolvable area in a TFT- or CCD-based digital imaging device
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| Dynamic range | show 🗑
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| exposure latitude | show 🗑
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| histogram | show 🗑
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| image noise | show 🗑
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| look up table (LUT) | show 🗑
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| matrix size | show 🗑
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| modulation transfer function (MTF) | show 🗑
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| show | the highest spatial frequency that can be recorded by a digital detector. Determined by the pixel pitch. The pixel pitch is determined by sampling frequency for cassette-based PSP systems and by DEL spacing for TFT flat panel. half the # of pixels/mm
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| show | an electronic element that converts light into charge. With indirect TFT detectrs this is accomplished by a light-sensitive amorphous silicon photodiode on top of the TFT array.
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| photoconductor | show 🗑
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| show | a "picture element", or pixel, the smallest area represented in a digital image. A digital radiography image consists of a matrix of pixels, which is typically several thousand pixels in each direction
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| pixel density | show 🗑
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| show | the space from the center of a pixel to the center of the adjacent pixel. It is measured in microns (um). Pixel pitch is determined by the DEL size or the sampling frequency.
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| processing algorithm | show 🗑
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| quantization | show 🗑
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| sampling frequency | show 🗑
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| show | a material that absorbs x-ray energy and re-emits part of that energy as visible light. Indirect TFT flat panel detectors use a scintillator. 2 modern high-eff x-ray scintillators are cesium iodide & gadolinim oxysulfide.
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| show | noise, especially quantum noise, ultimately limits our ability to see an object's edge (signal difference); SNR can be used to describe the edge conspicuity of a particular obj. under well defined exposure conditions.
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| spatial resolution | show 🗑
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| structured (needle) phosphor | show 🗑
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| thin film transitor (TFT) | show 🗑
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| tiling | show 🗑
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| turbid phosphor | show 🗑
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