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Physics > Ch 15 Computed Radiography > Flashcards

Ch 15 Computed Radiography Flashcards

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1
Q

CR is a type of ____

A

DR, it is just indirect

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2
Q

CR can produce better images at _______

A

lower patient dose

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3
Q

IP =

A

imaging plate

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4
Q

PD =

A

photodiode (circuitry)

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5
Q

PMT =

A

photomultiplier tube

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6
Q

PSL =

A

photostimulable luminescence (method of using a phosphor to store an image)

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7
Q

PSP =

A

photostimulable phosphor

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8
Q

SP =

A

storage phosphor

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9
Q

SPS =

A

storage phosphor screen

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10
Q

in CR the response to x-ray interaction is seen as:

A

trapped electrons in a higher energy metastable state (latent, not stable, energized)

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11
Q

PSL photostimulable luminescence is using an _____ to expose the IP and allow _____

A

different light (laser) to expose the IP and allow the latent image to be read

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12
Q

Many Compton interactions occur with outer-shell electrons sending them into an excited metastable state, when the electrons return to the ground state _____

A

visible light is emitted

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13
Q

True or False? over time the metastable electrons will return to ground state on their own?

A

True

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14
Q

the return of metastable electrons to the ground state can be accelerated or stimulated by ________

A

exposing the phosphor to intense infrared light from a laser (PSL)

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15
Q

the main PSP is _____

A

barium flurohalide

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16
Q

x-ray interaction with a photostimulable phosphor results in:

A

excitation of electrons into a metastable state

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17
Q

when metastable electrons return to their ground state:

A

visible light is emitted

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18
Q

the IP has lead backing that reduces _____ and improves _____

A

reduces backscatter and improves contrast resolution of the image receptor

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19
Q

thermoluminescent dosimetry (TLD) and stimulated luminescence (OSL) are:

A

the main radiation detectors used for occupational radiation monitoring

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20
Q

light is emitted when a TLD crystal is ____

light is emitted when a OSL crystal is ____

A

heated

illuminated

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21
Q

the beam diameter of the infrared light (laser) is:

A

50-100 micro meters

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22
Q

the diameter of the laser beam affects the:

A

spatial resolution of the CR imaging system

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23
Q

the laser beam causes metastable electrons to ________ with the emission of ______

A

return to the ground state with the emission of a shorter wavelength light in the blue region of visible spectrum

24
Q

after the IP is erased if there is any residual latent image it is removed by:

A

flooding the phosphor with very intense white light

25
Q

solid-state lasers produce _______ and therefore are less likely to ______

A

longer wavelength light and therefore are less likely to interfere with emitted light

26
Q

daylight film processors are based on:

A

wet chemistry processing

27
Q

the laser is the source of ______, however to spreads as it travels to the ______

A

source of stimulating light; travels to the rotating or oscillating reflector

28
Q

the drive mechanisms of the CR reader move the imaging plate slowly along its long axis while an ______ causes the stimulating mirror to sweep rapidly across the IP

A

oscillating beam deflection mirror

29
Q

_____ and ______ are the process of analog-to-dialog conversion (ADC)

A

Sampling and quantization

30
Q

the image buffer is usually _____

A

a hard disc

31
Q

a 14-bit CR image has _____ gray levels

A

16, 384

32
Q

the principle source of noise on a radiographic image is ______

A

scatter radiation

33
Q

______ patient radiation dose is possible with CR

A

lower

34
Q

CR image contrast is _____ regardless of _____

A

constant regardless of radiation exposure

35
Q

in CR images can be made at ____ kVp and _____ mAs, resulting in ______

A

higher kVp and lower mAs, resulting in reduction in patient radiation dose

36
Q

CR should be performed at _____ techniques than screen-film

A

lower

37
Q

CR is based on ____

A

PSL photostimulable luminescence

38
Q

x-rays interact with an _____ and for a latent image by exciting electrons to a higher energy metastable state

A

SPS storage phosphor screen

39
Q

in the CR reader the latent image is made visible by releasing the metastable electrons with a ______

A

stimulating laser light beam

40
Q

on returning to the ground state electrons emit a ______ in proportion to the intensity of the x-ray beam

A

shorter wavelength

41
Q

the emitted light signal is ____

A

digitized and reconstructed into a medical image

42
Q

the value of each CR pixel describes _____

A

a linear characteristic curve over four decades of radiation exposure and a 10,000 gray scale

43
Q

the wide latitude of CR results in ______

A

lower patient dose and improved contrast resolution

44
Q

λs

A

laser, infrared light, longer λ, low frequency, low energy, monochromatic, more intense bright light, red, small diameter (50-100 micro meters), better spacial resolution, stimulates latent image

45
Q

λe

A

emitted light, ultraviolet, shorter λ, higher frequency, higher energy, polychromatic, less bright, blue range, metastable electrons returning to stable state

46
Q

the latent image is created by:

A

photoelectric effect trapping electrons

47
Q

what are the phosphors that glow white?

A

Sbs

48
Q

fog from phosphor in CR cassette is called ______

A

turbid

49
Q

screen-film has ____ shades of gray and gives you _____ info and _____ spatial resolution

A

10³, less info, less spatial resolution

50
Q

CR has ____ shades of gray and gives you ______ info and ____ spatial resolution

A

10^4, more info, more spatial resolution

51
Q

dynamic range is:

A

the range of exposures that will give an acceptable radiograph

52
Q

we view the manifest image using _____ vision

A

photopic, cones

53
Q

horizontal trace is ___ info

A

useful

54
Q

the more metastable electrons there are the _______

A

more to the manifest image

55
Q

turbidity is ___ in color

A

cloudy

56
Q

ghosting is ____

A

residual white left from the image, must use a brighter light to erase it, same laser used to read it but it has a bigger diameter

Physics (13 decks)

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