Chapter 9: Key Terms (Digital Radiography)

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Analog

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Relating to the mechanism in which data is represented by continuously variable physical quantities.

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Artificial intelligence

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Ability of a computer to preform decision making similar to a human being.

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Charged-coupled device (CCD)

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A CCD is a solid-state detector used in many electronic devices such as a video cameras and fax machines. A CCD is used as the image receptor found in a digital sensors. Converts x-rays to electrons that are sent to a computer via a wire, or wirelessly via radio frequency.

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Complementary Metal Oxide Semiconductor (CMOS)

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A solid-state integrated circuit similar to the CCD. Used in digital radiography as an image receptor in the intraoral sensor. Converts x-rays to electrons that are sent to a computer via a wire, or wirelessly via radio frequency.;

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Digital Image

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Radiographic image that exists as bits of information in the computer file. Special computer software constructs an image on a monitor for viewing.

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Digital Imaging Communications in Medicine (DICOM)

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A joint committee formed in 1983 by the American College of Radiology and the National Electrical Manufactures Association to create a standard method for electronic transmissions of digital images, the goal of which is to achieve compatibility and ease exchange of electronic information between digital systems.

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Digital Radiograph

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See digital image

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Digital Subtraction

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Using a computer to superimpose two standardized radiographic images, causing the like areas of the image to “cancel” each other out, leaving only the changes visible.

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Digitize

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To convert an into a digital form that can be processed by a computer.

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Direct Digital Imaging

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A method of directly obtaining a digital image by exposing an intraoral sensor to x-rays to produce an image that can be viewed on a computer monitor.

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Gray Scale

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Refers to the total number of shades of gray visible in an image.

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Gray Value

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Number that corresponds to the amount of radiation received by a pixel within a digital sensor. The computer uses this value to determine the shade of gray displayed on the computer monitor.

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Indirect Digital Imaging

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Photostimuable phosphor (PSP) plate sensor technology. Method of obtaining a digital image in which an exposed phosphor plate is placed into a scanner and then converted into a digital image.

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Line Pair

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Refers to the number of paired lines visible in 1 mm of an image. The more line pairs visible, the better the spatial resolution in an image.

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Noise

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See electronic noise. The digital equivalent to film fog. An electrical disturbance that clutters the digital image reducing image clarity and contrast.

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Photostimuable Phosphor (PSP)

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Digital imaging sensors that use rare earth phosphor (barium europium fluorohalide) coated plates. When exposed to x-rays, the PSP sensor or plate “stores” the x-ray energy until stimulated by a laser beam to produce a digital image.

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Pixel

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Small, discrete units of digital information that together constitute an image. Pixel is a term shortened from the word “Picture” and “element” (pix=plural of picture; el=element).

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Sensor

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For use in digital imaging. An electronic or specially coated plate that is sensitive to x-rays. Placed intraorally to capture a radiographic image when exposed to x-rays.

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Solid State

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Specifically means, no moving parts. Refers to digital image sensors, usually CCD or CMOS technology.

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Spatial Resolution

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The discernable separation of closely adjacent image details that contributes to image sharpness. The greater the spatial resolution, the sharper the image appears. When referring to a digital image, sharpness is determined by the number and size of pixels measured in line pairs. When the number of pixels is low, the image appears to have jagged edges and becomes difficult to see.

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Storage Phosphor

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Usually composed of europium activated barium fluorohalide, coating on a photostimulable phosphor plate used in indirect imaging. The storage phosphor “stores” the x-ray energy similar to the way silver halide crystals within film emulsion store a latent image. A scanning device is used to release the stored energy to be converted to a radiographic image on a computer monitor.

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x-coordinate

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One of two values assigned to dimensions of a pixel that tell the computer where the pixel is located. Computer software uses the x-coordinate along with the y-coordinate to reconstruct digital data captured by a sensor or photostimuable plate into a radiographic image displayed on a monitor.

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Y-coordinate

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One of two values assigned to dimensions of a pixel that tell the computer where the pixel is located. Computer software uses the y-coordinate along with the x- coordinate to reconstruct digital data captured by a sensor or photostimuable plate into a radiographic image displayed on a monitor.