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Imaging Lecture Rad 142 > lecture final > Flashcards

lecture final Flashcards

1
Q

In a variable KVP technique chart, for every cm increase in part thickness, the kvp is changed by:

A

increasing 2kvp

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2
Q

The phosphor coated detector in the AEC system does what?

A

converts radiation to light

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3
Q

where is the detector located in the exit type AEC system?

A

underneath or behind cassette

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4
Q

what does the capacitor do in the AEC system?

A

stores the electrical current

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5
Q

the phtotomultiplier tube is a _______ tube and does what?

A

vacuum tube, produces the electrical current

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6
Q

what produces the ion (electrical current) in the ionization chamber AEC system?

A

exit/image forming radiation

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7
Q

what factors will affect image density produced by an AEC system?

A

CR improperly centered
pathology
incorrect bucky switch selected

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8
Q

what is the direct square law used for? (old mAs/new mAs)

A

adjust the mAs when the SID is altered to maintain density

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9
Q

Collimating down from a 14x17 to an 8x10 field size, how will your technical factors need to be adjusted?

A

mAs increased by 60%
OR
add 10 Kvp

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10
Q

collimating down from a 14x17 to a 10x12 field size, how will your technical factors need to be adjusted?

A

mAs increased by 40%
OR
add 5 Kvp

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11
Q

fast speed screens: Phosphor size and layer, recorded detail/spatial resolution, mottle, dose, amount of mAs required

A
  • large crystals, thick layer
  • less recorded detail/ spatial resolution
  • more mottle and noise
  • decreases patient dose
  • 200 speed screen requires 50% less mAs than 100 speed screen
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12
Q

slow speed screens: Phosphor size and layer, recorded detail/spatial resolution, mottle, dose, amount of mAs required

A
  • small crystals, thin layer
  • more recorded detail/spatial resolution
  • less mottle/noise
  • increases patient dose
  • 100 speed screen would require 100% more mAs than a 200 speed screen would
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13
Q

in screen/film emulsion, what is the sensitivity speck?

A

a defect or flaw in the crystalline structure of screen/films liver bromide crystal. Its also a trap where black metallic silver is formed as the latent image

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14
Q

in a CR imaging plate, phosphors are stimulated with what’?

A

xray photon energy and fluoresce

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15
Q

what is developer oxidation?

A

refers to the giving up of electrons by developer reducing agents to reduce the silver atoms to black metallic silver to create the visible image.

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16
Q

what does developer selectivity mean?

A

the developer only reduces the exposed silver bromide crystals and leaves the unexposed intact.

17
Q

what does the transport system do?

A

provides mechanical movement of film thru the processor at a controlled rate

18
Q

what does the circulation system do?

A

responsible for agitation of the chemistry and constant filtering of the developer

19
Q

what does the fast acting reducing agent establish?

A

gray and white shades of the visible/manifest image

-component of developer

20
Q

what does the slow acting reducing agent establish?

A

black tones of the visible manifest image

-component of developer

21
Q

what do the reducing agents do?

A

reduces exposed silver bromide crystals to black metallic silver and changes the latent image into a visible manifest image
-component of developer

22
Q

what does the activator do?

A

swells the films emulsion

-component of developer

23
Q

what is the pre hardeners job?

A

shrinks and hardens the films emulsion, prevents films from getting stuck together
-component of developer

24
Q

what does the retrainer/antifog agent do?

A

prevents the reduction of unexposed silver bromide crystals

-component of developer

25
Q

what does the acidifier do?

A

neutralizes/stops the developer action and further development of the film
-component of the fixer

26
Q

what does the hardener do?

A

shrinks and hardens the films gelatin emulsion
makes the image permanent for storage archival quality
-component of the fixer

27
Q

what happens when the fixer malfunctions?

A

leaves the film sticky or wet
milky residue
emulsion turns yellow or brown

28
Q

what happens when there is server under replenishment or the developer?

A

developer becomes oxidized or depleted
exposed crystals are undeveloped
density speed and contrast decrease
film emulsion will swell and stick to roller
makes transport and drying of the film difficult

29
Q

what occurs when the dryer system malfunctions?

A

wet or damp fils exiting the processor

30
Q

to calculate the average gradient on an H&D curve, what two points must be added to the base plus fog?

A

OD 2.00 or 2.50 and 0.25

31
Q

describe the digital image receptor curve

A

wide dynamic range
better visualization
linear curve
more responsive

32
Q

describe the film sensotometric response curve

A

limited dynamic range
S shaped curve
less responsive

Imaging Lecture Rad 142 (4 decks)

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