Exam 1 Flashcards
(129 cards)
0
Q
+D artifacts appear?
A
black on img
1
Q
artifact?
A
undesirable OD’s on the img
2
Q
-D artifacts appear what?
A
white
3
Q
3 categories of film artifacts?
A
exposure, processing, & handling
4
Q
pressure type artifacts usually _______________ and appear as ___________
A
sensitize emulsion; appear as higher OD (+D)
5
Q
artifacts that scrape emulsion appear as
A
lower OD (-D)
6
Q
guide shoe marks?
A
run II to direction of film travel on leading edge
7
Q
pi line artifact runs ______ to direction of film travel
A
perp
8
Q
dichroic stain usually applies to?
A
chemical fog
9
Q
dichroic stain aka
A
curtain effect
10
Q
what causes dichroic stain
A
inadequate processing, where chems run down leading edge of film (yellow, purple, or blue)
11
Q
what causes fog?
A
too high temp or too high humidity (+60%)
12
Q
fog is what kind of film artifact?
A
handling (storage)
13
Q
what causes static artifact?
A
low humidity (-40%) & friction
14
Q
what type of artifact is a static artifact?
A
handling artifact
15
Q
static artifacts look like?
A
tree, crown, smudge (+D)
16
Q
half moon marks?
A
from bending/kinking film (+D)
17
Q
scratch/finger nail marks (as pressure artifact) appear?
A
+D
18
Q
artifact from moisture on finger?
A
-D, white
19
Q
dirty screens cause __D artifact?
A
-D
21
Q
static artifact is +D from what?
A
buildup of e-‘s in emulsion
22
Q
hypo retention?
A
yellow/brown stains after a long storage T due to hypo retention from the fixer
23
Q
what type of artifact is hypo retention?
A
handling
24
Q
hypo retention is caused by what?
A
inadequate washing
25
processing artifacts are eliminated w what 2 things?
a proper processor QC program and frequent cleaning
26
proper facility design helps reduce?
handling/storage artifacts
27
acceptable QC program has 3 steps:
acceptance testing, routine performance monitoring, & maintenance
28
misalignment must not exceed
2% of SID
29
3 tools used to measure focal spot size:
pinhole camera, star pattern, & slit camera
30
measured kVp should be w/in
10% of indicated kVp
31
exposure timer accuracy should be w/in 5% of indicated time for
exposure T’s more than 10 ms
32
____% acceptable for exposure T’s of 10 ms or less?
20%
33
exposure linearity must be w/in
10% for adjacent mA stations
34
sequential rad exposures should be reproducible to w/in
+/- 5%
35
digi rad IRs have unique artifacts assoc w
pixel failure
36
enviro rad can contrib to
ghosting
37
flatfielding is a software correction that is done to equalize
the response of ea pixel to a uniform XR beam
38
Lossless compression up to ____ generally is considered acceptable and helpful in digi rad img management
3:1
39
histogram?
graph of frequency of occurrence v digital value intervals
40
histogram is a ______ plot
discrete
41
automatic rad field recognition is essential for?
artifact-free imgs
42
what prevents histogram errors that can lead to artifacts? (2)
proper coll & centering
43
partitioning of multiple digi img’s on single IP results in
proper separation & coll of ea img
44
wet pressure sensitization appears as?
+D
45
QA deals w
ppl
46
QC deals w
instrumentation & equipment
47
monitor equipment performance deals w?
QC
48
calibration done by?
QC
49
most equipment performance should be monitored
annually or when something is replaced
50
principally the _________ is responsible for QC
medical physicist
51
5 characteristics focused on by QC:
spatial res, contrast res, temporal res, SNR, &
| artifacts
52
QC guidelines developed by:
American College of Radiology (ACR)
53
what is the state required filtration?
2.5 mm of Al
54
filtration is measured in terms of what?
HVL
55
filtration is evaluated how often?
annually (or when something is replaced)
56
collimation should not exceed
2% of SID
57
coll. is evaluated how often?
semi-annually
58
centering indicator must be accurate to
1% of SID
59
focal spot size determines
spatial res
60
focal spot size is typically measured w?
pinhole/slit camera, star pattern
61
focal spot size can alternatively be measured w?
line pair test tool
62
line pair test shows what to indicate + spatial frequency --> + spatial res
+ line pairs
63
what has most lp's (& best spatial res)?
mammo
64
__% change in kVp —> visible change in OD?
4%
65
kVp calibration: measured kVp should be w/in
10% of indicated kVp
66
____% accuracy of indicated exposure T for exposures GREATER than 10 ms (exposure timer accuracy)
5%
67
___% accuracy for exposure T LESS than 10 ms (exposure timer accuracy)
20%
68
exposure timer accuracy is responsible for?
pt dose
69
exposure timer accuracy measured on?
irradiation T of ion chamber or photodiode
70
[automatic exposure control (AEC)] back up timer should terminate exposure at…(2)
6 s or 600 mAs, whichever occurs first
| or, at 1.5 x’s the original exposure
71
what is exposure linearity?
many combo’s of the mA and exposure T must produce same mAs value
72
exposure linearity must be w/in
10% of adjacent mA stations
73
(other than exposure linearity) ___________ must be w/in 10% btw adjacent mA stations
mR/mAs values
74
exposure linearity measured w
radiation dosimeter
75
(exposure reproducibility) rad exposure should be reproducible to w/in
5%
76
(exposure reproducibility) output rad intensity should not vary more than
5%
77
what should be cleaned w soft, lint-free cloth & anti-static sol.
intensifying screen
78
intensifying screens should be cleaned how often?
at least every other mo.
79
screen film contact is measured how?
w wire mesh test
80
screen film contact should be evaluated how often?
semi-annually
81
protective apparel should be checked?
annually
82
used to measure light intensity for film illuminator?
photometer
83
film illuminator light intensity should not vary more than
10%
84
if you change 1 bulb, you have to?
change ALL bulbs (even in adjacent view boxes in the room)
85
development temp?
95º F (37º C)
86
3 types of digi rad artifacts?
IR artifacts, software artifacts, object artifacts
87
IR artifacts? (5)
rough handling, scratches, dust, residual glue, ghost img
88
ghost img from?
incomplete erasure
89
if CR IP has not been used for_____, it should be erased again before use
24 hrs
90
software artifacts: (2)
dead pixels, failure of electronic processing
91
interpolation?
(software) mathematical process of assigning a digi value to a dead pixel based on recorded value of adjacent pixels
(correctional algorithm)
92
flatfielding can minimize effect of
irregular patterns
93
software correction that is performed to equalize the response of ea pixel to a uniform XR beam
flatfielding
94
ensures a uniform response on the pixels
flatfielding
95
compression when fine detail not required
Lossy
96
object artifacts: (4)
tech error in pt positioning, coll., histogram selection, & backscatter
97
what can you do to avoid backscatter?
put a shield behind the IR
98
a plot of the frequency of appearance of a given object characteristics
histogram
99
histogram is ____________ v. _____________
frequency of occurrence v. digi value intervals
100
shape varies w ea anatomical projection in a what?
histogram
101
what occurs if the XR exposure field is not properly collimated, sized, & positioned
exposure field recognition errors
102
exposure field recognition errors can lead to ________________ bc of signal outside of exposure field being included in the histogram
histogram anal. errors
103
proper coll. & centering prevent what kind of errors that can lead to artifacts?
histogram errors
104
allows 2+ img’s to be projected onto single IP
partitioning
105
img field must be oriented w the size & dimension of the IP to avoid img artifacts
alignment
106
any undesirable densities on the processed img (other than those caused by scatter rad or fog)
artifacts
107
how do you reduce backscatter?
coll.
108
4 IP artifacts & how they appear on img?
cracks —> lucent —> -D
tape residue —> -D
hair —> -D
backscatter —> +D
109
intermittent appearance of extraneous line patterns
plate reader artifacts
110
dirt on light guide appears as? (late reader artifact)
horizontal white lines
111
plate reader loading multiple IP’s in a single cassette appear as (plate reader artifact)
ghost
112
moiré pattern error (2 causes)
when grid lines are II to plate reader’s laser scan lines &
| when grid frequency matches scanning frequency (frequency harmonics)
113
debris on mirror in laser printer appear as
fine white lines
114
what operational error causes unattenuated rad striking IP —> histogram will be changed so it is outside normal exposure indicator range for selected body part?
insufficient coll.
115
should use smallest IP possible & proper coll.
| to avoid what kind of error?
operational error
116
upside down IP appears as?
white grid-type pattern & white areas that correspond to hinges
117
underexposure produces
quantum mottle
118
how do you fix quantum mottle?
+ mAs
119
overexposure affects what? how?
contrast (decreases contrast)
120
what causes overexposure?
insufficient kVp
121
what acquisition error causes inaccurate pixel values?
incomplete charge transfer
122
if exposures taken in too rapid sequences it could cause what?
electronic memory artifact
123
it is acceptable to perform a _________ instead of measuring focal spot size (for spatial res)?
line pair test
124
comparing the mR output at 50 mA @ .2 s, 100 mA @ .1s is part of a test for
linearity
125
most common processing artifacts (film) are?
pressure artifacts
126
most pressure artifacts are caused by what?
transport system of processor
127
guide shoe marks appear as?
-D (II to film travel)
128
pi line marks appear as?
+D (perp to film's direction)
129
artifact that looks like pi lines but are not spaced 3.14" apart?
scratch artifact
