Term
| direct digital radiography (DDR) |
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Definition
- use sensor instead of silver halide film
- electronic production of radiographic image
- composed of thousands of pixels, each represented by a number |
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Definition
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Definition
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Definition
| - x-rays of radiation that exit patient is recorded on electronic sense as altered pattern of electrons |
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Term
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Definition
- samples voltages in small discrete groups
- assigns number to each voltage |
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Definition
| - assigns number to each voltage |
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Term
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Definition
| - samples voltages in small discrete groups |
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Term
| CCD charge coupled device |
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Definition
- thin silicon layer arranged in pixel matrix created by electrodes at back
- may have scintillator
- electrons trapped in "charge packets" in proportion to number of x-rays hitting sensor
- 1 charge packet = 1 pixel |
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Term
| charge coupled device (CCD) |
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Definition
- charge packets move through bucket brigade to computer through cable
- sampled/quantized by analog digital converter |
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Term
| complementary metal oxide semiconductor (CMOS) |
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Definition
- design similar to CCD
- each pixel connected to transistor
- no bucket brigade
- signal sent to computer through cable |
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Term
| photostimulable phosphor plates (PSP) |
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Definition
- very similar to film
- reusable
- flexible
- thin
- no wires |
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Term
| photostimulable phosphor plates |
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Definition
- europium ions added as imperfections on purpose
- plate of barium fluorohalide in crystal lattice
- x-rays excite Eu electrons to metastable state beyond valence band |
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Term
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Definition
| - similar to silver halide |
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Term
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Definition
- plate scanned by red laser
- trapped EU electrons released and emit visible light
- light is converted to voltage
- sampled/quantized by ADC |
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Term
| true! it clears any extra electrons |
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Definition
| T/F: before PSP exposure, white light is ok. |
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Term
| false, it will make the image lighter the longer it is in white light |
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Definition
| T/F: it is ok to expose PSP digital to light after it has been exposed. |
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Term
| false! red light exposes the latent image and will erase image! |
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Definition
| T/F: the red safelight in a dark room is ok to use with PSP digital film. |
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Term
| false! saliva on gloves will ruin processor |
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Definition
| T/F: it is ok to wear gloves to put the PSP sensor in the scanner |
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Term
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Definition
- ability to distinguish closely spaced object
- measure in line pairs/mm
- depends on size of pixels |
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Term
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Definition
- film radiograph: 20 lp/mm
- DDR: 10 lp/mm
- doesn't really make a difference, we can only perceive 6 lp/mm |
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Term
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Definition
- ability to distinguish varying densities
- depends on differential attenuation of radiation in tissues
- depends on ability of imaging system to reproduce differences in attenuation |
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Definition
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Definition
pixel value of 0 is represented as ____.
pixel value of 255 is represented as ___. |
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Definition
| - ability of imaging receptor to capture a range of x-ray exposures |
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Term
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Definition
| T/F: film, CCD, CMOS have similar latitudes |
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Term
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Definition
| T/F: PSP has a greater latitude than film, CCD or CMOS |
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Term
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Definition
- loses no data
- image exactly the same after reconstruction
- maximum compression ratio 3:1
- ex: bitmap, tiff |
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Term
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Definition
- discards redundant information
- ratios as high as 33:1
- ex: jpeg |
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Term
| x-rays originate from small focal point |
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Definition
- acts like numerous point sources
- each point source forms own image
- images are always unsharp |
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Term
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Definition
- x-rays travel in diverging lines
- divergence projects edges of objects farther away from each other than they actually are |
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Term
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Definition
- structures of 3 dimensions but are projected onto a 2 dimensional film
- different parts are varying distances from film
- magnification is different at each distance |
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Term
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Definition
| - blurring at the edge of an image |
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Term
| all of the above are true |
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Definition
penumbra is minimized by all of the following except
- long PID
- small focal spot
- no motion of patient
- film close to teeth
- all of the above are false
- all of the above are true |
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Term
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Definition
- equal enlargement of all parts of image
- reduced by same things as penumbra |
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Term
| penumbra and magnification |
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Definition
___ reduced by
- long PID
- short object-film distance
- small focal spot |
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Term
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Definition
| - unequal enlargement of parts of the image |
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Term
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Definition
____ reduced by
- parallel alignment of teeth and film
- perpendicular alignment of central ray
- NOT related to PID or object-film distance |
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Term
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Definition
- long PID length
- short object-film distance
- small focal spot
- film and object parallel
- x-ray beam at right angle to film |
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Term
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Definition
which of the following will increase the average energy of the x-ray beam?
- increase kVp
- decrease exposure time
- increase mA
- decrease PID length
- decrease added filtration |
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