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Radiology Vcast05 > chapters 17 and 18 radio physics > Flashcards

chapters 17 and 18 radio physics Flashcards

(71 cards)

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1
Q

is it ever appropriate to repeat overexposed digital images?

A

no, unless there is analog-to-digital converter saturation

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2
Q

what does saturation cause in an image

A

causes the image to be clipped or burned out

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3
Q

what is data clipping

A

data is removed from the diagnostic range that can’t be recognized b/c it is above or below the diagnostic range
(OCCURS WHEN ADC REACHES SATURATION)

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4
Q

Philips DR uses __________ numbers

A

sensitivity (S)

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5
Q

Agfa CR uses_____________ numbers

A

log median exposure (LgM)

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6
Q

GE DR uses____________ numbers

A

detector exposure index (DEI)

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7
Q

Siemens uses_________ numbers

A

Exposure index (EXI)

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8
Q

what is the relation between S number and the amount of radiation striking the IP

A

the relationship is Inversely proportional

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9
Q

(EDR) exposure data recognizer is what?

A

optimal reading conditions are determined once the auto mode processing processes the image data in the IP

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10
Q

what allows more than one view be exposed on a single IP?

A

(EDR) Exposure data recognizer

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11
Q

what are the VOI (values of interest) for a Fuji

A

full anatomic area

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12
Q

what are the VOI (values of interest) for a Konica

A

recognition of relevant anatomy

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13
Q

how can you balance AEC

A

there are lots of ways b/c every manufacture comes up with different ways

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14
Q

does the EI number or the DI number have a direct relation to patient exposure

A

no there is no relation between EI/DI numbers and patient exposure

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15
Q

deviation index gives what to the technologist?

A

gives feedback to the technologist regarding technique and image quality based on signal-to-nosie ratio

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16
Q

what does a DI (deviation index) of 0 indicate

A

indicates that their is no diff. between the desired EI and the actual EI

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17
Q

diffrent IRs have________ detective quantum efficiency (DQE)

A

diffrent

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18
Q

A high DQE results in ______ noise level

A

lower

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19
Q

what is a usual EI number derived from

A

the mean detector entrance exposure which is derived from the MEAN PIXEL VALUE of the image

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20
Q

what is the dynamic range

A

the number of shades of gray an imaging system can produce

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21
Q

how do you calculate the amount of shades of gray

A

2^# of bit

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22
Q

what kind of function do Digital receptors have in a graph

A

linear receptor response function

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23
Q

CR and DR receptors____________ and does not________

A

can receive any radiation exposure; experience the toe and shoulder limitation of film/screen exposures

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24
Q

areas that receive very little radiation can be enhanced by the _____ instead of being______

A

computer; clumped at the toe

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25
areas that receive greater exposure can be _____ into _____ instead of being _________
separated; visible densities; clumped around the shoulder
26
what = bite depth
2^n
27
how many bits make up a byte
8 bits make up 1 byte
28
spatial resolution
the ability to see small objects or fine recorded detail
29
spatial frequency
unit of line pairs per millimeter (ip/mm or in digital # of cycles/mm or micrometer
30
what happens to the image when we have a very high spatial resolution
this will increase blur even though the resolution will be better
31
which imaging system has the best spatial resolution
mammography 12 IP/mm
32
Modulation transfer function (MTF)
responsible for converting contrast values of diff. sized objects into contrast intensity levels in the image
33
what does high spatial frequency create
blur; results in reduced modulation- reduced amplitude of the signal
34
as spatial frequency increases what happens to MTF (transfer of object contrast to image contrast)
MTF (modulation transfer function) will go decrease
35
I.S spatial resolution is spatial frequency at ___ MTF
10%
36
spatial frequency and MTF make up what
Spatial resolution
37
in film screen radiography, what is the spatial resolution
8 Ip/mm
38
what spatial resolution does mammography have
15 Ip/mm (minimal blur)
39
what tool is used to measure spatial resolution in digital
lead bar pattern test tool
40
what tool is used to measure spatial resolution in conventional units
resolution test tool
41
the___ the # of line pairs the_____ the spatial resolution
greater, higher (remember we need a balance of line pairs and MFT)
42
what are the primary factors of spatial resolution
matrix size, pixel size and pixel pitch
43
pixel size in relation to spatial resolution
the smaller the pixel size the better spatial resolution
44
pixel pitch is what
the space from the center of a pixel to the center of the adjacent pixel
45
what does a narrow pixel pitch do to spatial resolution
increases spatial resolution
46
what is the spatial resolution for conventional radiography and CR
10 Ip/mm, 5Ip/mm (dynamic range makes up for it because it allows more contrast resolution due to its ability to give more detail
47
PSF
point spread function function unit (vert. line creates a point when it intersects with the horizontal imaging plane)
48
LSP
line spread function unit (vert. line creates a point when it intersects with the horizontal imaging plane)
49
ESF
Edge spread function unit (vert. line creates a point when it intersects with the horizontal imaging plane)
50
noise
degeneration of image begins with increased image noise (low mAs and kVp create this)
51
a 10x12 IP with 2k pixels will have a ______ spatial resolution than a 7x7 IP with 2k pixels b/c of the pixel size
worse
52
Pixel Size (formula)
FOV/ Matrix Size
53
DQE (detective quantum Efficiency)
is the measurement of x-ray absorption efficiency
54
what does high DQE do to patient dose
it should decrease patient dose
55
what is the speed class (DQE)
reflection of the amount of light (PSP); the level of exposure received by the IP (THE MEASURE OF X-RAY ABSORPTION EFFICIENCY)
56
a luminescent level of 200= how much speed class
200 speed class
57
what happens when speed class increases in relation to noise
noise will increase (b/c kVp is increased and mAs Isi decreased causing desist fluctuations as speed class increases
58
the exposure index is ______ proportional to the speed class of operation
indirectly proportional
59
E.I increased from 1400 to 1700 the speed class is ______ from 400 to ______
reduced, 200
60
image noise is what
a fluctuation is density/ overall brightness
61
if the signal is higher than the noise this will = ?
better spatial resolution
62
S/N; 10/1= 10
good spatial resolution
63
S/N; 1/10= .1
bad spatial resolution
64
what specific part of the dynamic range controls contrast resolution in DR?
the ADC via the bite depth (2^n)
65
does mAs affect contrast resolution?
yes mAs does have an effect on contrast resolution
66
what process ensures that unnecessary info., such as scatter, outside the collimated edges become eliminated from the histogram analysis
(PRIEF) pattern recognizer for irradiated exposure field
67
Auto mode processing?
allows IP image data to be sampled and used by the EDR
68
what determines the range of the histogram data that should be included in the displayed image
VOIs
69
a value that reflects the diff. between the desired or target exposure to the IR and the actual exposure to the IR is the
deviation index
70
DI (deviation index) above 0=
increased exposure
71
DI (deviation index) below 0=
decreased exposure

Radiology Vcast05 (18 decks)

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