RTE 1418 Exam Review Flashcards
which kVp selection (high or low) will result in more scattered XRs in the img-forming beam?
high
Decreasing kVp will increase?
pt dose, img noise, Compton scatter, OD
pt dose
3 things that improve contrast resolution
tight coll, lowering kVp, pt compression
the use of a compression device will increase?
contrast
the use of ______ improves contrast and reduces pt dose
collimation
how can you improve img contrast w a heavy pt w/o increasing pt dose?
use tight collimation
img contrast improves when more of ______ rad is removed
scattered
a grid is constructed w _______ strips and ______ interspace material
radiopaque, radiolucent
an XR w a long scale contrast will also have _____ latitude and _____ contrast
wide, low
grids are designed to remove scattered XRs before they reach?
the IR
what is the grid ratio of a grid w 3-mm height, 0.025-mm thick lead grid strips, and 0.3-mm thick interspace material?
10:1
foreshortening is caused by a(n)
angled body part when the beam is perpendicular to the IR
OD is directly controlled by changing the _____
mAs
pt thickness affects img quality by affecting what 3 things?
magnification, rad contrast, & focal spot blur
the best way to min. magnification is to use a
long SID and small OID
subject contrast is affected by
pt thickness
3 primary factors influencing the intensity of scatter in the img-forming beam are
kVp, field size, & pt thickness
scatter rad increases as ______ increases
field size
the most commonly used beam restricting device is the
variable collimator
the positive beam limiting device (PBL) ensures that the XR beam is collimated to
the IR size
_______ is the degree of difference in the OD btw areas of an img
contrast
what does the angle of the scattered photon, the height of the grid strips, and the width of the interspace material have in common?
the amount of scatter absorption in a grid depends on these factors
what is the formula for grid ratio?
h/D
the purpose of a grid is to achieve?
improved img contrast
the interspace material in grids are made of?
aluminum and/or plastic fiber
grids generally have a frequency of ______ lines per inch
60-110
grids generally have a frequency of ______ lines per cm
25-45
the most critical consideration when using a crossed grid is
alignment (positioning latitude)
how could contrast be improved on a bedside XR of a very large pt?
use grid, use tight coll., lower kVp
which is the linear grid w the widest latitude for centering and focus?
(6:1, 10:1, 12:1. 16:1)
6:1
spatial resolution improves with decreased? (3)
screen blur, motion blur, and geometric blur
radiographic _______ is random fluctuation in the OD of an XR
noise
the slope of the _______ portion of the char. curve shows the film contrast
straight line
if 10% of the view box light is transmitted through an area of film, what is the OD in that area?
1
a film w a char. curve showing a high slope would be useful when ________ is needed
high contrast
the 3 primary geometric factors affecting img qual are?
magnification, distortion, & focal spot blur
distortion can be reduced by?
placing the object plane II to IR
focal spot blur can be reduced using a
small focal spot
XR img qual. is improved when the ________ is increased
SID
High speed IRs generally produce XRs w?
increases noise
the ability to img 2 separate objects and visually detect one from the other
resolution
an IR w __________ can be used over a greater range of exposures
wide latitude
formula for OD?
OD=log base 10(original intensity/transmitted intensity),
OD=log10(Io/It)
the densities above 2.5 on a film are represented in the _____ portion of the char. curve
shoulder
sharpness of detail can be improved by increasing ______
SID
(Char. curve) film w highest contrast
steeper slope
(Char. curve) film w highest speed
curve closest to y-axis
(Char. curve) film w widest latitude
wider slope
(Char. curve) film w short-scale contrast
steeper slope
lowering kVp _______ pt dose and _______ img contrast
increases, increases
modern rad film base is made of?
polyester
how thick is rad film base?
150-300 µm
crystals in film emulsion consist of _____ & _____
silver bromide, silver iodide
latent img formation occurs during film _____
exposure
a contaminent in the SHC (silver halide crystal) creates the
sensitivity speck
the latent img can be seen?
only after development
the latent img is made up of _____ atoms
silver
high contrast film contains _____ SHC of _____ size
smaller, uniform
film is made w double emulsion to enhance film ______
speed
spectral matching is not a consideration when using?
direct exposure film (bc you need an IS)
storing film in very low humidity conditions can cause _______
static artifacts
film should be stored at a temp of _____ or below and w humidity no higher than ______.
a. 20ºF, 70%
b. 68ºF, 10%
c. 68ºF, 40%
d. 75ºF, 60%
c. 68ºF, 40%
the rollers in the auto processor are part of the ______ system
transport
replenishment of fixer and developer are controlled by the?
microswitch
the undeveloped silver halide is removed from the emulsion during?
fixing
which of the following is a rare earth phosphor? (zinc cadmium sulfite lanthanum oxybromide barium fluorohalide silver bromide)
lanthanum oxybromide
an increase in _____ will increase both beam qual. and quant.
kVp
what are the 4 primary exposure factors?
kVp, mA. time, and SID
changes in kVp affect (3)
OD, img contrast, img noise
an increase in mAs causes (an) _____ in beam qual. and (an) ______ in beam quant.
no change, increase
there is a direct relationship btw the quant. of XRs and the ________
milliamperage
if mAs are increased from 20 mAs to 40 mAs, the pt dose will….
be doubled
beam penetrability is increased if ____ is increased
kVp
beam qual. and beam quant. are increased by (2)
increasing kVp; (or going from single-phase to three-phase voltage)
beam qual. is improved when the _____ is increased, but the ______ has no effect on beam qual.
kV, mA
which technique would be best for reducing img blur?
a. 90 kVp/400 mA @ 0.01 sec
b. 85 kVp/50 mA @ 0.08 sec
c. 75 kVp/200 mA @ 0.02 sec
d. 65 kVp/100 mA @ 0.04 sec
a. 90 kVp/400 mA @ 0.01 sec
which techniques would give the highest pt dose?
a. 90 kVp/200 mA @ 0.02 sec
b. 87 kVp/400 mA @ 0.02 sec
c. 74 kVp/400 mA @ 0.04 sec
d. 65 kVp/300 mA @ 0.1 sec
d. 65 kVp/300 mA @ 0.1 sec
which imaging system provides the highest beam quantity? (3-phase, 12-pulse 3-phase, 6-pulse high frequency single phase, fully rectified)
3-phase, 12-pulse
added filtration has the effect of _____ the img quality and ______ pt dose
increasing, reducing
when all other exposure factors remain the same, changes in focal spot size result in ______ in beam quality and _____ in beam quantity
no change, no change
film can turn brown during storage due to retention of _________
ammonium thiosulfate
filtration is added to XR machines during manufacturing so that the required total of ____ mm Al equivalent filtration is achieved
2.5
radiographic _____ is random fluctuation in the OD of an XR
noise
what kind of film is used in mammo?
single emulsion film
an exposure w an off-level grid will show grid cutoff
across the img
what is the grid ratio of a grid w 3-mm height, 0.025-mm thick lead grid strips, and 0.3-mm thick interspace material?
10:1
what is the formula for Bucky factor?
pt dose w grid/pt dose without grid
grid ratio is the ____ of the grid strips divided by the width of the _______
height, interspace material
tree artifacts are caused by
friction
high contrast XR has what type of contrast?
short scale contrast
if a tech did a knee XR w a non-grid exposure using 10 mAs and wanted to use an 8:1 grid, what mAs should be used to produce an XR w the same density?
40
a tech did a lat C-spine using a 12:1 grid and 10 mAs. if the tech wants to repeat w/o a grid, what should the new mAs be to produce an XR w the same density?
2
if a tech uses 24 mAs w a 16:1 grid, how much mAs should they use w a 6:1 grid?
12
which technique chart causes less rad dose to the pt?
fixed kVp chart
the mAs value must be changed ___% to produce a perceptible change in OD
30
low humidity in the darkroom can cause
tree static
the undeveloped silver is removed from the emulsion during?
fixing
ea cell of an img matrix is called?
pixel
which of the following has the greatest effect on digi img resolution? (frequency, img contrast, noise, matrix size)
matrix size
visually, dynamic range refers to what?
the # of shades of gray that can be represented
PACS
picture archiving and communication system
an advtg of digi over conventional imaging
more latitude
which of the following devices is used for computed radiology? (photo stimulable phosphor plate [PSP], radiographic film, heat sensitive detectors, intensifying screens)
PSP
a CR latent img is made manifest by what method?
laser stimluation
what is used in indirect digi rad to convert light photons into an electrical charge?
amorphous silicon
what is used in direct digi rad to convert XR photons into an electrical charge?
amorphous selenium
which system for recording XR imgs produces best spatial resolution
screen-film system
if the matrix size of a digi XR system is 1024 what will be the bit depth?
10
what determines the resolution in digi rad? (3)
PSP thickness, pixel size, laser beam diameter
what is the resolution in computed radiography? (lp’s)
3-5 line pairs/mm
what is the resolution in film? (lp’s)
10 lp/mm
what is the resolution in mammo? (lp’s)
15 lp/mm
when insufficient light is produced, the img will be grainy, a condition known as?
quantum mottle
which artifact occurs when the grid frequency is close to the laser scanning frequency in a computer radiography?
Moiré
which layer of the imaging plate helps to reduce static electricity?
conductive layer
which following laser beam diameter produces best spatial resolution?
(50 nm, 100 nm, 150 nm, 700 nm)
50 nm
what is the bit depth if the dynamic range is 128?
7
if the bit depth is 9, how many shades of gray will be present?
512
sm or lg cassette size will produce best resolution?
sm
log mean of afga and exposure index number is
directly proportional
what is the normal value of exposure index in Kodak (Carestream)
2000
what chems are used in digi rad indirect system?
cesium iodide & amorphous silicon
does slow or fast screen speeds produce the best detail?
slow
the _____ represents zero or one
bit
in computer lang ______ is a “word”
2 bytes
the latent img is formed on the _____ for digi rad
radiation detector
in digi rad, the brightness of the of the img is determined by
pixel values
spatial resolution is improved w increased _________ in digi rad
matrix size
the dynamic range determines the degree of ______ in the img
contrast resolution
the typical matrix size for digi rad is ______
1024 x 1024
computed radiography utilizes _______ for latent img formation
photostimulable phosphor
computers operate using a binary machine language. this lang uses binary digits to compute data. a binary digit is referred to as what?
Bit
which can be used to adjust img brightness?
window level
what can be used to adjust img contrast (post processing)?
window width
the # of shades of gray levels present in a digital img is known as
dynamic range
pixel size relates to
spatial resolution
what elements are used in gas lasers
He/Ne
the # of visible shades of gray in a digi img is determined by
bit depth
the dynamic range determines the degree of ______ in the img
contrast resolution
how can you min. quantum mottle?
+ mAs, - kVp, slow IR
what is contrast resolution?
ability to img 2 objects and visually distinguish btw the 2
how does fast IR speed affect detail?
high noise, low res
how does slow IR speed affect detail?
low noise, high res
if the speed of IR is doubled, how do you maintain density?
1/2 mAs
whats sensitometry?
relationship btw exposure I and blackness (density) on img
whats on x-axis for sensitometric curve?
LRE
whats on Y-axis for sensitometric curve?
OD
formula for OD?
OD=log(Lo/Lt)
Lo-original light, Lt-transmitted light
diagnostically useful density range for rad img?
0.25-2.5
if 36000 light beams strike a film and 36 beams pass thru, what is OD?
3
rad contrast is the product of ______ contrast and _____ contrast
IR & subject
how do you calculate slope of the char. curve?
calculate avg gradient
formula for avg gradient?
avg gradient = (OD2-OD1)/(LRE2-LRE1)
how are contrast and latitude related?
inversely
3 principal geometric factors that affect rad quality?
sharpness, distortion, blur
2 formulas to calculate Magnification Factor (MF)?
MF=img size/object size;
MF=SID/SOD
4 factors that affect magnification?
size, shape, SID, OID
shape distortion?
unequal magnification of diff portions of same object
5 geometric factors that affect distortion
object thickness/shape/pos, OID/SID
what is spatial distortion?
misrepresentation in the img of the actual spatial relationship among objects
focal spot blur is ____ on the anode side and ____ on the cathode side of img
sm; lg
5 geometric factors that affect subject contrast? (or pt factors that affect XR quality)
pt thickness, tissue mass density, effective Z, object shape, kVp
motion blur is more visible using ____ SID and ____ OID
short; long
3 factors that control amount of scatter produced?
kVp, field size, pt thickness
will cone or cylinder produce better contrast?
cone
f(x) of 1st stage entrance shutter?
prevent off-focus rad
pt dose is _____ w high ratio grid
increased
height of pb strips = 12 mm, spaced 1 mm apart. what is grid ratio?
12:1
crossed/linear; which produces more contrast?
crossed
formula for Bucky Factor (B)?
B = incident remnant XRs/transmitted img-forming XRs, or B = pt dosed w grid/pt dose without grid
higher the grid ratio the _____ the Bucky factor/contrast improvement factor
higher
bucky factor increases w ________ kVp
increasing
purpose of moving grid
remove grid lines
if grid is off level, will img be over or underexposed?
underexposed (light img)
how will img appear if grid is off center?
cutoff across entire img; underexposed, light img
how will img appear if grid is place Upside-down?
peripheral cut off
“archival quality” =
permanence
4 layers of film
- supercoat
- emulsion
- adhesive layer
- film base
which film causes more rad dose to pt’s and why?
single emulsion (less speed, more exposure required)
“lateral decentering” means?
off-center grid
cross-over is unique to _________ film w IS
double-emulsion film
cross-over is reduced by (2)
T-grains & anti-crossover layer
XR system where only mAs is selected and factors are auto-adjusted to highest mA and shortest exposure T allowed by high-frequency generator
falling load denerator
what is cross-over, what does it increase?
light from one IS crosses film base & exposes emulsion on opp. side of base ; increases blur
film contrast depends on
size and distrib. of SHCs
ideal temp/humidity to store film?
68 F & 40-60% humidity
storing film at a high temp causes?
fog
effect of storing film at low humidity
static artifact
4 layers of IS?
- protective layer
- phosphor layer
- reflecting OR absorbing layer
- base
what is the diff btw reflecting and absorbing layer in IS?
reflecting (+ speed, - detail); absorbing (- speed, + detail)
fluorescence?
ability of phosphors to emit visible light only while exposed to XRs
phosphorescence?
when phosphors contin. to emit light after XR exposure has stopped; aka “scree-lag/afterglow” –> fog
sensitivity specks w 3+ Ag atoms ea does what?
creates a latent img center (appears as density on the img)
what does the use of an IS do to pt dose and detail?
decreases both
how do you check for screen film contact?
wire mesh test
what happens during developing (is this product acidic or alkaline)
(acidic) latent –> visible img
what happens during fixing (acidic or alkaline)?
removes remaining SHC from emulsion (makes img permanent); alkaline
what material is used as fixing agent?
ammonium thiosulfate (“hypo”) - alkaline
does mAs influence contrast?
yes has effect on img quality (not primarily), but has no effect BEAM qual
what is the effect of using kVp to manipulate density?
low kVp has + differential absorption, high kVp has - differential absorption
OD?
degree of blackening on the img
what effect does focal spot size have on quantity?
none
what is the change in beam quantity when changing from half wave rectification to a full wave rectification?
quant doubles
what is the percentage of body habitus for asthenic and hyposthenic
asthenic 10%
hyposthenic 35%
what is the effect on beam quality when changing from half wave rectification to full wave rectification?
no change in quality
mAs must be changed __% to produce perceptible change in OD
30
kVp must be changed __% to produce perceptible change in OD
4
what causes a histogram analysis error? (3)
improper coll., off-focus/scatter, grid cut off
high kVp does what to dose?
decreases
use of AEC does what to dose?
reduces
are lungs and soft tissue more/less likely to be saturated?
(saturated = LOTS of rad) more likely
high exposure and low noise determines what in digi?
high contrast res
how much do you increase kVp to double exposure?
15%
how much do you increase mAs to double exposure?
double
what does grid cut off do to the img on a digi system? on film?
(digi) low contrast and appearance of quantum mottle
(film) too bright
(digi) extreme overexposure can create _____ contrast
low
what is the appropriate grid frequency for stationary grid in CR?
150+ lines/in
chems used in PSP?
Ba Fluoro Halide, coated w Europium
which laser wavelength gives better resolution?
long wavelength
______ & ______ are the process of ADC
sampling, quantization
what is a line pair?
a high contrast line separated by an interspace of equal width (one line + one interspace)
what is spatial frequency?
line pairs in a given length (lp/mm)
img system w higher spatial frequency will have better what?
spatial res
modulation transfer f(x) (MTF)?
ratio of img to object as a f(x) of spatial frequency (ideal MTF is 1)
spatial res in screen film rad is principally determined by?
focal spot size
the greater the area of TFT, the greater the?
DQE
what detects the emitted blue light from the IP and amplifies it before sending it to the digitizer?
photomultiplier
what does the digitizer do?
divides the analog img into matrix and assigns ea pixel a # based on brightness
what happens to spatial res when you increase FOV?
decreases (pixels get bigger)
FOV/matrix size, determines what?
spatial res
speed in digi is determined by what?
amount of PSL (photostimulable luminescence)
+ PSL –> + speed –> - rad exposure
exposure indicator for fuji?
(indirect) S# 200-400
exposure indicator for Kodak/Carestream?
(direct) Ei 2000
Exposure indicator for Afga?
(direct) log mean - 2.2
