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radiology BODC year 2 > digital processing > Flashcards

Flashcards in digital processing Deck (7)
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why is digetal better

- improved dynamic range of images (similar to photoshop, can improve brightness, contrast, quality)
- digital processing is very fast
- digital storage, retrieval and transport (PACS) – cant lose the radiograph or mistake it with someone elses


how is the image captured

- image is captured with a sensor
- image then transformed into series or binary number (0 and 1)


types of sensors that cn be used

- computed radiography (CR)
- CCD (charge coupled device)/ CMOS(complementary metal oxide semi conductor) – similar to mobile phone camera


digital radiography how does it work (CCD/CMOS)

- sensor has lots of photodiodes, uses the intermediate step of light production to form image
- or CCD, x ray photons fall onto the phosphor and emit a small flash of light
- the silicon of the receptor acts as a photodiode and converted the light emitted by the phosphor to electrical charge
- the intensity of electrical charge is directly proptional to the light flash which is directly proportional to amount of radiation that fell onto the photodiode
- the charge pattern formed from the pixels in the sensor matric forms the radiographic image


resolution is measured by

line pairs per mm


what can you do with digital photograpjhy

manipulate the image to increase its diagnosis value


problems with digital receptors

1) Laser malfunction
- scan sensor with laser
- one at a time, sequential
- if beam not smooth process can produce dark line/bands

2) Sensor wrong way round/back to front
- easy to spot on film
- white circle (foil) on one side of receptor and not on the other

3) PSP delaminating
- plastic backing with barium fluro… on one side of the slide
- sometimes can start to delaminate
- on the edges of film start to separate
- see white artefact with uneven edge
- sensor need to replaced
4) Bends in PSP
- can over bend film
- can see linear white lines that cross the censor usually along the curvature of the sensor
- adapt to patient mouth
- can get a crack in the phosophor – thin radiopaque line (can be mistken with instruments
- doesn’t have flutes or spirals which endodontic files have