Ch 15 Computed Radiography

Question 1

CR is a type of ____

Answer 1

DR, it is just indirect

Question 2

CR can produce better images at _______

Answer 2

lower patient dose

Question 3

IP =

Answer 3

imaging plate

Question 4

PD =

Answer 4

photodiode (circuitry)

Question 5

PMT =

Answer 5

photomultiplier tube

Question 6

PSL =

Answer 6

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

Question 7

PSP =

Answer 7

photostimulable phosphor

Question 8

SP =

Answer 8

storage phosphor

Question 9

SPS =

Answer 9

storage phosphor screen

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

visible light is emitted

Question 13

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

Answer 13

True

Question 14

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

Answer 14

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

Question 15

the main PSP is _____

Answer 15

barium flurohalide

Question 16

x-ray interaction with a photostimulable phosphor results in:

Answer 16

excitation of electrons into a metastable state

Question 17

when metastable electrons return to their ground state:

Answer 17

visible light is emitted

Question 18

the IP has lead backing that reduces _____ and improves _____

Answer 18

reduces backscatter and improves contrast resolution of the image receptor

Question 19

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

Answer 19

the main radiation detectors used for occupational radiation monitoring

Question 20

light is emitted when a TLD crystal is ____

light is emitted when a OSL crystal is ____

Answer 20

heated

illuminated

Question 21

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

Answer 21

50-100 micro meters

Question 22

the diameter of the laser beam affects the:

Answer 22

spatial resolution of the CR imaging system

Question 23

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

Answer 23

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

Question 24

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

Answer 24

flooding the phosphor with very intense white light

Question 25

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

Answer 25

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

Question 26

daylight film processors are based on:

Answer 26

wet chemistry processing

Question 27

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

Answer 27

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

Question 28

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

Answer 28

oscillating beam deflection mirror

Question 29

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

Answer 29

Sampling and quantization

Question 30

the image buffer is usually _____

Answer 30

a hard disc

Question 31

a 14-bit CR image has _____ gray levels

Answer 31

16, 384

Question 32

the principle source of noise on a radiographic image is ______

Answer 32

scatter radiation

Question 33

______ patient radiation dose is possible with CR

Answer 33

lower

Question 34

CR image contrast is _____ regardless of _____

Answer 34

constant regardless of radiation exposure

Question 35

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

Answer 35

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

Question 36

CR should be performed at _____ techniques than screen-film

Answer 36

lower

Question 37

CR is based on ____

Answer 37

PSL photostimulable luminescence

Question 38

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

Answer 38

SPS storage phosphor screen

Question 39

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

Answer 39

stimulating laser light beam

Question 40

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

Answer 40

shorter wavelength

Question 41

the emitted light signal is ____

Answer 41

digitized and reconstructed into a medical image

Question 42

the value of each CR pixel describes _____

Answer 42

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

Question 43

the wide latitude of CR results in ______

Answer 43

lower patient dose and improved contrast resolution

Question 44

λs

Answer 44

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

Question 45

λe

Answer 45

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

Question 46

the latent image is created by:

Answer 46

photoelectric effect trapping electrons

Question 47

what are the phosphors that glow white?

Answer 47

Sbs

Question 48

fog from phosphor in CR cassette is called ______

Answer 48

turbid

Question 49

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

Answer 49

10³, less info, less spatial resolution

Question 50

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

Answer 50

10^4, more info, more spatial resolution

Question 51

dynamic range is:

Answer 51

the range of exposures that will give an acceptable radiograph

Question 52

we view the manifest image using _____ vision

Answer 52

photopic, cones

Question 53

horizontal trace is ___ info

Answer 53

useful

Question 54

the more metastable electrons there are the _______

Answer 54

more to the manifest image

Question 55

turbidity is ___ in color

Answer 55

cloudy

Question 56

ghosting is ____

Answer 56

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