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13 Cards in this Set

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What is the makeup of a digital image?
-all digital images are composed of a grid of rows & columns (matrix) of tiny picture elements called pixels
-each pixel has a color or shade of gray
-most exposed pixel in a digital rad is assigned black, least exposed pixel is assigned white, regardless of technique
What is spatial resolution?
ability to define or separate 2 objects close together

spatial resolution of 0.1 mm means that a lesion that is 0.1 mm can be discerned
Exposure factors are usually (higher/lower) w/ digital systems vs. film-screen systems.
higher
What is main difference b'twn film-screen systems & digital systems?
method by which radiation is detected after x-rays pass thru patient

digital: x-ray exposure measured on electronic medium & converted to a digital image in DICOM format
What are the characteristics of CR?
computed radiography
$60-100K

-CR cassettes are physically similar to film cassettes but contain an imaging plate rather than intensifying screens & film
-imaging plates must be read in a plate reader before x-ray exposure information is sent to computer: ~90 s/plate
-images better than w/ film (better latitude): as good as DR?
What are the characteristics of DR?
direct digital imaging
$100K+

imaging plate is independent of any cassette (built directly into x-ray table or is portable)
-imaging plates send signal measured from x-ray beam directly to a computer --> faster image generation than w/ CR
-excellent quality image
What are some advantages of digital radiography systems?
-better image contrast: easier to see some lesions
-very forgiving of radiographic technique settings: less retakes d/t exposure
-post-processing: can adjust blackness & contrast after the fact
-clients will be impressed
-can transmit images electronically for consulation
-more convenient storage
-no more lost images, assuming backup
-don’t have to maintain darkroom, buy film, etc.
-wide latitude (dynamic range)
What are some disadvantages of digital radiography systems?
-don’t have degree of spatial resolution possible w/ film-screen radiography: of little clinical relevance
-initial investment can be considerable
-must be compatible w/ rest of hospital system
What is PACS?
picture archiving & communication system (PACS): centralized computer storage system

provides storage, dissemination functions, & links images w/ demographic data
What is DICOM?
digital imaging communications in medicine (DICOM): specific image file format analogous to JPEG and TIF formats commonly used in manipulation & storage of digital camera images

-must have DICOM viewing software to view files
-file sizes are very large compared to regular digital photos
-make sure your images are really DICOM compliant: some vendors change files slightly so they aren’t compatible w/ all viewers
Inherent detail in digital rads (is/is not) as good as with film based rads.
is NOT

it is the improved contrast resolution that appears to give digital rads more detail
What is latitude (dynamic range)?
range of exposures that result in useable image

enables the viewing of both soft tissues and bone on the same image without repeat exposures at different techniques, as would be needed for a film-screen system
More pixels/area = (greater/less) detail
greater