Exam 1 Flashcards
+D artifacts appear?
black on img
artifact?
undesirable OD’s on the img
-D artifacts appear what?
white
3 categories of film artifacts?
exposure, processing, & handling
pressure type artifacts usually _______________ and appear as ___________
sensitize emulsion; appear as higher OD (+D)
artifacts that scrape emulsion appear as
lower OD (-D)
guide shoe marks?
run II to direction of film travel on leading edge
pi line artifact runs ______ to direction of film travel
perp
dichroic stain usually applies to?
chemical fog
dichroic stain aka
curtain effect
what causes dichroic stain
inadequate processing, where chems run down leading edge of film (yellow, purple, or blue)
what causes fog?
too high temp or too high humidity (+60%)
fog is what kind of film artifact?
handling (storage)
what causes static artifact?
low humidity (-40%) & friction
what type of artifact is a static artifact?
handling artifact
static artifacts look like?
tree, crown, smudge (+D)
half moon marks?
from bending/kinking film (+D)
scratch/finger nail marks (as pressure artifact) appear?
+D
artifact from moisture on finger?
-D, white
dirty screens cause __D artifact?
-D
static artifact is +D from what?
buildup of e-‘s in emulsion
hypo retention?
yellow/brown stains after a long storage T due to hypo retention from the fixer
what type of artifact is hypo retention?
handling
hypo retention is caused by what?
inadequate washing
processing artifacts are eliminated w what 2 things?
a proper processor QC program and frequent cleaning
proper facility design helps reduce?
handling/storage artifacts
acceptable QC program has 3 steps:
acceptance testing, routine performance monitoring, & maintenance
misalignment must not exceed
2% of SID
3 tools used to measure focal spot size:
pinhole camera, star pattern, & slit camera
measured kVp should be w/in
10% of indicated kVp
exposure timer accuracy should be w/in 5% of indicated time for
exposure T’s more than 10 ms
____% acceptable for exposure T’s of 10 ms or less?
20%
exposure linearity must be w/in
10% for adjacent mA stations
sequential rad exposures should be reproducible to w/in
+/- 5%
digi rad IRs have unique artifacts assoc w
pixel failure
enviro rad can contrib to
ghosting
flatfielding is a software correction that is done to equalize
the response of ea pixel to a uniform XR beam
Lossless compression up to ____ generally is considered acceptable and helpful in digi rad img management
3:1
histogram?
graph of frequency of occurrence v digital value intervals
histogram is a ______ plot
discrete
automatic rad field recognition is essential for?
artifact-free imgs
what prevents histogram errors that can lead to artifacts? (2)
proper coll & centering
partitioning of multiple digi img’s on single IP results in
proper separation & coll of ea img
wet pressure sensitization appears as?
+D
QA deals w
ppl
QC deals w
instrumentation & equipment
monitor equipment performance deals w?
QC
calibration done by?
QC
most equipment performance should be monitored
annually or when something is replaced
principally the _________ is responsible for QC
medical physicist
5 characteristics focused on by QC:
spatial res, contrast res, temporal res, SNR, &
artifacts
QC guidelines developed by:
American College of Radiology (ACR)
what is the state required filtration?
2.5 mm of Al
filtration is measured in terms of what?
HVL
filtration is evaluated how often?
annually (or when something is replaced)
collimation should not exceed
2% of SID
coll. is evaluated how often?
semi-annually
centering indicator must be accurate to
1% of SID
focal spot size determines
spatial res
focal spot size is typically measured w?
pinhole/slit camera, star pattern
focal spot size can alternatively be measured w?
line pair test tool
line pair test shows what to indicate + spatial frequency –> + spatial res
+ line pairs
what has most lp’s (& best spatial res)?
mammo
__% change in kVp —> visible change in OD?
4%
kVp calibration: measured kVp should be w/in
10% of indicated kVp
____% accuracy of indicated exposure T for exposures GREATER than 10 ms (exposure timer accuracy)
5%
___% accuracy for exposure T LESS than 10 ms (exposure timer accuracy)
20%
exposure timer accuracy is responsible for?
pt dose
exposure timer accuracy measured on?
irradiation T of ion chamber or photodiode
[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
what is exposure linearity?
many combo’s of the mA and exposure T must produce same mAs value
exposure linearity must be w/in
10% of adjacent mA stations
(other than exposure linearity) ___________ must be w/in 10% btw adjacent mA stations
mR/mAs values
exposure linearity measured w
radiation dosimeter
(exposure reproducibility) rad exposure should be reproducible to w/in
5%
(exposure reproducibility) output rad intensity should not vary more than
5%
what should be cleaned w soft, lint-free cloth & anti-static sol.
intensifying screen
intensifying screens should be cleaned how often?
at least every other mo.
screen film contact is measured how?
w wire mesh test
screen film contact should be evaluated how often?
semi-annually
protective apparel should be checked?
annually
used to measure light intensity for film illuminator?
photometer
film illuminator light intensity should not vary more than
10%
if you change 1 bulb, you have to?
change ALL bulbs (even in adjacent view boxes in the room)
development temp?
95º F (37º C)
3 types of digi rad artifacts?
IR artifacts, software artifacts, object artifacts
IR artifacts? (5)
rough handling, scratches, dust, residual glue, ghost img
ghost img from?
incomplete erasure
if CR IP has not been used for_____, it should be erased again before use
24 hrs
software artifacts: (2)
dead pixels, failure of electronic processing
interpolation?
(software) mathematical process of assigning a digi value to a dead pixel based on recorded value of adjacent pixels
(correctional algorithm)
flatfielding can minimize effect of
irregular patterns
software correction that is performed to equalize the response of ea pixel to a uniform XR beam
flatfielding
ensures a uniform response on the pixels
flatfielding
compression when fine detail not required
Lossy
object artifacts: (4)
tech error in pt positioning, coll., histogram selection, & backscatter
what can you do to avoid backscatter?
put a shield behind the IR
a plot of the frequency of appearance of a given object characteristics
histogram
histogram is ____________ v. _____________
frequency of occurrence v. digi value intervals
shape varies w ea anatomical projection in a what?
histogram
what occurs if the XR exposure field is not properly collimated, sized, & positioned
exposure field recognition errors
exposure field recognition errors can lead to ________________ bc of signal outside of exposure field being included in the histogram
histogram anal. errors
proper coll. & centering prevent what kind of errors that can lead to artifacts?
histogram errors
allows 2+ img’s to be projected onto single IP
partitioning
img field must be oriented w the size & dimension of the IP to avoid img artifacts
alignment
any undesirable densities on the processed img (other than those caused by scatter rad or fog)
artifacts
how do you reduce backscatter?
coll.
4 IP artifacts & how they appear on img?
cracks —> lucent —> -D
tape residue —> -D
hair —> -D
backscatter —> +D
intermittent appearance of extraneous line patterns
plate reader artifacts
dirt on light guide appears as? (late reader artifact)
horizontal white lines
plate reader loading multiple IP’s in a single cassette appear as (plate reader artifact)
ghost
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)
debris on mirror in laser printer appear as
fine white lines
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.
should use smallest IP possible & proper coll.
to avoid what kind of error?
operational error
upside down IP appears as?
white grid-type pattern & white areas that correspond to hinges
underexposure produces
quantum mottle
how do you fix quantum mottle?
+ mAs
overexposure affects what? how?
contrast (decreases contrast)
what causes overexposure?
insufficient kVp
what acquisition error causes inaccurate pixel values?
incomplete charge transfer
if exposures taken in too rapid sequences it could cause what?
electronic memory artifact
it is acceptable to perform a _________ instead of measuring focal spot size (for spatial res)?
line pair test
comparing the mR output at 50 mA @ .2 s, 100 mA @ .1s is part of a test for
linearity
most common processing artifacts (film) are?
pressure artifacts
most pressure artifacts are caused by what?
transport system of processor
guide shoe marks appear as?
-D (II to film travel)
pi line marks appear as?
+D (perp to film’s direction)
artifact that looks like pi lines but are not spaced 3.14” apart?
scratch artifact
