Appendix for Digital Image Acquisition and Display
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| show | the devel. of a-si materials,have the same structure as single crystals over short distances but are less ordered over larger distances, has enabled fabrication of flat-panel TFT arrays large enough to be used as the basis for all flat panel XR detec
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| Amorphous selenium (a-Se) | show 🗑
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| Automatic rescaling (Auto ranging, rescaling, scaling, normalization) | show 🗑
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| Bit depth | show 🗑
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| show | a photgraphic detector. None are in use except for intraoral dental imaging.
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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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| show | the range of receptor exposures that provides a quality, low-noise imageat an appropriate patient exposure consistent with ALARA. Exposure latitude is not the exposure range which will be rescaled to consistent image brightness.
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| histogram | show 🗑
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| show | all images have unwanted fluctuations in brightness that are unrelated to the object being imaged. These are collectively described as image noise.
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| show | the default gradient curve applied to the data set of your image determining the intial display contrast. The LUT can be adjusted after the initial image processing has been applied.
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| matrix size | show 🗑
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| show | a measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution. every image can be described in terms of the amount of energy for each of its spatia frequency components.
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| Nyquist frequency | show 🗑
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| photodiode | show 🗑
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| show | amorphous selenium TFT detectors, the a-Se layer forms a continuous x-ray-sensitive photoconductor that converts x-ray energy directly to charge. This charge can be directly "read out" by the TFT array. A photodiode is not necessary with a-Se detectors.
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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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| show | a term that describes the number of pixels/mm in an image. pixel density is determined by the pixel pitch.
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| pixel pitch | show 🗑
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| show | the mathematical codes used by the software to generate the image appearance desired by the viewer. The processing algorithm includes gradient processing (brightness and contrast), frequency processing (edge enhancement and smoothing), and others
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| quantization | show 🗑
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| sampling frequency | show 🗑
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| scintillator | show 🗑
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| signal to noise ratio (SNR) | show 🗑
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| spatial resolution | show 🗑
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| show | a phosphor layer with columnar phosphor crystals within the active layer. Resembles needles lined up on end and packed together.
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| thin film transitor (TFT) | show 🗑
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| tiling | show 🗑
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| show | a phosphor layer with a random distribution of phosphor crystals within the active layer. this layer can be used in both cassette-based and cassette-less systems and is similar to a standard intensifying screen used with film.
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