finals Flashcards
Unit for effective dose
Sv & REM
Unit for absorbed dose
Gy & RAD
Becquerel is a unit of
radioactivity
Coulombs/kg is a unit of
exposure
equation for inverse square law
I1/I2 = (D2)^2/ (D1)^2
equation for grid ratio
h/d
equation for GCF (nongrid –> grid)
mAs (grid)/ mAs (w.o grid)
Higher grid ratio means ___ (2)
better scatter clean up
better contrast
equation for GCF (grid –> another)
mAs1/mAs2 = GCF1/GCF2
equation for wavelength
w = c/f
equation for frequency
f = c/ w
ionization radiation = ___ wavelength = _____ frequency
short, high
unit for frequency
hertz (Hz)
rank longest to shortest wavelength
radiowave
microwave
infrared light
visible light
UV light
xray
gamma rays
cosmic rays
5 characteristics of Xray
- highly penetrating (short wave, high frequency)
- cannot be reflected or focused
- neutrally charge
- no mass
- travels in straight line
high penetrating, low ionization is ___
gamma
low penetrating, high ionization
alpha
which radiation produced at the anode
primary
beams with different energy is called ___ (aka ___ radition)
heterogenous - primary
What are considered primary radiation
Brems & characteristics
Brems produced ____ xray spectrum
continuous
Characteristics produced ___ xray spectrum
discrete
primary beam photons have keV energy of ___
30-40% kVp
What are considered secondary radiation
scatter & leakage
what is produced by the energy of primary beam redirected after interacting with matter
scatter
scatter radiation does not produce __
quantum mottle
scatter radiation effect on images (3)
produce noise
reduce contrast resolution
makes image less visible
how do we reduce scatter (4)
- decrease volume of tissue
- decrease kVp
- increase collimation
- increase atomic #
decrease kVp = ___ scatter
reduce
increase atomic # = ___ scatter
decrease
what devices are used to reduce scatter (3)
collimator
beam-restring devices
grid
which beam-restring devices is the simplest? and which is the most effective in scatter cleanup
simplest: aperture diaphragm
effective: cone
which of the following is not beam-restricting devices:
a. aperture diaphragm
b. grid
c. collimator
d. cones
e. all of the above are beam-restring devices
B
what is the purpose of grid
reduce scatter radiation that reached IR
what is beam restrictors and grid have in common
reduce scatter
reduction in total # of xray photons remaining in beam after passing thru given thickness of material is ___
a. HVL
b. attenuation
B
thickness of absorbing material required to reduce x-ray intensity to half of its original value is ___
a. HVL
B. attenuation
A
what does HVL measures?
a. quantity
b. quality
A
2 ways to remove low-energy photons
filteration
hardening of beam
remove low-energy photons = ___ patient dose
decrease
High-voltage generator is ___ circuit
secondary
Components of primary circuit (5)
- power supply
- autotransformer
- kVp meter
- timer
- step-up transformer
what controlled autotransformer?
a. kVp selector
b. mA adjusment
A
What operate autotransformer
self-induction
what component of the circuit directly determine V
autotransformer
AEC timer utilized ____ for exposure control
ionization chamber
cons of AEC backup timer
too short = underexposed image
AEC measures ___ of radiation reached IR
a. quantity
b. quality
A
mA selector controls ___ in the circuit
amperage
Rectifiers are located in ___ circuit
secondary
which component transform AC to DC
rectifiers
Rectifiers is ___ diode
solid state semiconductor
half wave have ____ diodies
full wave have __ diodes
0,1,2
4
ionization chamber is radio___
radiolucent
what does rectifier require to operate
voltage rectification
what does high-voltage transformer require to operate
AC
Which component increase voltage from autotransformer by a fixed amount
step-up transformer
what does filament circuit control
degree & saturation the filaments are heated
what activate step-down transformer
a. kVp seelctor
b. mA adjustment
B
3 parts of high-voltage generators
step-up transformer
filament transformer
rectifiers
increase amperage = increase in __
of e- boiled off
the filaments are at which side of the tube
cathode
Tube housing can reduce ____
leakage radiation
Tube housing can prevent ___
electric shock
what is used in the tube housing as an insulator & thermal cushion
OIL
why glass is used for tube envelope
withstand heat
tube window for useful beam to exit is located in ___
glass envelope
TUbe current related to ___
mAs
what components are on the cathode side?
filament coil
focusing cup
function of filament coil
emits electrons when heated
function of focusing cup
confines electron beam to a small area of anode
what components are on the anode side
target
rotor
stator
functions of anode (3)
- electrical conductor
- mechanical support for target
- thermal dissipater
Xray emission source is at __
a. effective focal spot
b. actual focal spot
B
why tungsten is chosen as material for target (3)
- high atomic #
- high thermal conductivity
- high melting point
____ effective focal spot
____ actual focal spot
small
large
a sharper image will have ___ focal spot
small effective
pros & cons of small effective focal spot
pros: better spatial resolution
cons: more heat concentration
xray emission source is at ___
actual focal spot
xray are produced at ___
actual focal spot
Bremsstrahlung radiation interacts with
The nuclear field
Characteristic radiation interacts with
inner shell electrons
Characteristic radiation produced at ___ kVp
above 70
The xray primary beam most often consists of
Brems radiation
The energy of the beam can be changed through adjustments in
a. kvp
b. mas
c. quantity
d. distance
kVp
Off-foused radiation happend at the ___
anode
Target is on ___ side
anode
off focused radiation produced
ghosting effect
what helps reduce the amount of off-focused radiation
upper shutter of collimator
rotor is made up of ___
copper shaft & soft iron
stator consists of ___
electromagnet
Incident e- in photoelectric interacts with
inner shell e-
incident e- in compton interacts with
outer shell e-
what are ejected from photoelectric
photoelectron
what are ejected from compton
electron with ionizing capability
what happened when xray strike matter
- absorbed (photoelectrically)
- scatter
- direct transmission
reduction in intensity results from ____
absorption & scattering
increase kVp = __ PE = ___ Compton
decrease / increase
decreased patient dose = ___ PE = ___ Compton
decrease/ increase
Which of the following is not required for xray production
a. accelerating of e-
b. slowing of e-
c. rotating target
d. source of free e-
c. rotating target
Compton scatter most likely occurs with
a. An xray interacting with an outer shell electron
b. projectile electron interacting with outer shell e-
A
The anode heel effect causes
a. An x ray field with lower intensity on the anode side
b. xray with lower contrast
c. xray with higher quality on anode side
An x ray field with lower intensity on the anode side
thicker body part is placed on which side of xray tube
cathode
increase anode heel effect = ____ angle
small
increased anode heel effect = ___ SID
decreased
The line focus principle explains the relationship between:____
a. The actual focal spot and the effective focal spot
b. The large focal spot and small focal spot
c. The large focal spot and actual focal spot
A. The actual focal spot and the effective focal spot
Line focus principle results in greater ____ & ____
heat capacity
image sharpness
For line focus principle, what needed to be angled for heating while maintaining small focal spot
TARGET
Quantity aka ____ (3)
xray output
intensity
exposure
quantity is affected by ____ (4)
kvp
mas
distance
filtration
quantity is measured by _____
milliroentgens
Quantity is also known as all of the following except :____
a. xray output
b. exposure
c. energy
d. intensity
C
IR exposure is measured by ___
numeric exposure value
Quality aka ___
penetrability
HIGH penetration in material of ____ atomic #
LOW
quality is affected by ____ (2)
kvp
filtration
increase mAs = ____ quantity
increase
increase kVp = ____ quantity
increased 4x
increase distance = ___ quantity
decrease
increase filtration = ____ quantity
decrease
intensity is _____
a. quantity
b. quality
A
increase kVp = ____ speed + energy of photons
increase
what can remove low-energy photons
increase filtration
increase filtration = ___ resolution
increase
Beam quality is a measurement of
a. Half-value layer
b. beam divergence
c. amount of radioactivity
d. amount of xray in primary beam
A
What are the prime factors
kvp
mas
distance
what material is used for filtration
aluminum
thicker filters = ___ atomic # = ____ reduction of output
high
high
purpose of filtration
remove low-energy xray photons
filtration ____ intensity of beam AND ____ photon energy
decrease
increase
total filtration is combination of ____
a. inherent & added
b. inherent & compensating
c. added & compensating
A
purpose of grid
improve contrast by absorbing scatter
when to use grid
body thickness over 13cm or 10 for film
kvp > 70
grid is made up of ____ strips & ____ interspace
radiopaque
radiolucent
Grid lines could be visible in all of the following except ___
a. when using stationary grid
b. when the bucky oscillates
c. when CR is not perpendicular to IR
B
which type of grid has the tube angled with length of grid without cut-off
parallel
which type of grid has focal range
focused
grid with wide focal range = ____
low grid ratio
better scatter cleanup = ____ grid raatio
high
narrow focal range = ____ grid ratio
high
which type of grid has 2 linear grids perpendicular to one another
crosshatch
which type of grid is best at scatter cleanup
crosshatch
if primary beam is angled into lead and leads to decrease in density along periphery of film, what error occured?
grid cut-off
how to fix off-level grid
grid perpendicular to CR
when does off-focused error occur
when used at SID out of focal rang
which type of error is describes:
“ focused grid not aligned with labeled tube side facing ray tube”
upside down
what is the effect caused by upside-down grid error
uneven exposure
What caused moire effect
grid lines captured & parallel to scan lines
moire effects occured in ____ grid
stationary
HVL is a measurement of beam ____
a. quantity
b. quality
A
5 image characteristics
brightness
contrast
noise
distortion
spatial resolution
brightness is measured by ____
candela
brightness is controlled by ____
a. postprocessing
b. preprocessing
a
window level adjusts ___
a. brightness
b. contrast
A
increase window level = ___ brightness
decrease
why we dont adjust window width for brightness
data from original histogram is lost
narrow dynamic range –> misdiagnosed
contrast is ____ of pixel
bit depth
contrast describes:
a. visibility
b. sharpness
A
distortion describes:
a. visibility
b. sharpness
B
brightness & contrast corresponds to :
a. visibility
b. sharpness
A
distortion & spatial resolution corresponds to :
a. visibility
b. sharpness
B
sharpness is determined by ____ (3)
matrix size
pixel size
bit depth
sharpness is measured by ___ (4)
PSF
LSF
MTF
system noise
increased kVP = ___ scale
short
decreased kVp = ____ scale
long
short scale is for which structure
skin
bone
long scale is for which structure
soft tissue
Window width adjusts ____
a. brighness
b. contrast
B
What is the amount of mAs that can compensate for kVp
NONE
subject contrast depends on ____
kvp & irradiated material
subjected contrast resulted from ____
differential absorption
increased subject contrast = ___ kVp
decrease
spatial resolution aka ____ (3)
definition, sharpness, recorded detail
short wavelength = __ frequeny & resolution
increase
short wavelength is for ___ objecct
small
problems with spatial resolution (4)
no motion
decreased OID
decreased focal spot size
increase SID
if SNR increased = ____ image quality
increased
how do you optimize SNR
noise intolerance
set exposure value
monitor
noise intolerance = ____
exposure creep
lack of attention to wide dynamic range = ____
dose creep
decreased noise will ___
increase pt dose
difference bw optimal image and best image
optimal: balance of noise & pt dose
best: no noise & high pt dose
what caused size distortion
magnification
decreased magnification = ___ spatial resolution
increase
increase visualization = increased in ___ while maintaining____
OID
SID
minimize OID = ____ distortion
decrease
maximize SID = ____ distortion
increase
why shape distortion happen
object plane & image plane not parallel
shape distortion depends on what factors (3)
thickness
position
shape
how to decrease shape distortion
body // IR and perpendicular to CR
minimize OID
elongation is a type of ___ distortion
shape
elongation is caused by ____
a. tube angle
b. body part
tube angle
foreshortening is a type of ___ distortion
shape
foreshortening is cause by ____
a. tube angle
b. body part
body apart
Attenuation varies depend on ____ (2)
pt thickness & composition
differential absorption & attenuation depend on ____ (3)
- atomic #
- mass density
- xray energy
increase atomic # = ____ attenuation
increase
pathology will cause changes in _____ (3)
thickness
effective atmoic #
density
Additive is a condition in which ___
there is an increase in thickness, effective atmoic #, and/or density
additive conditions ____ attenuation
increase
as additive disease worsens, IR exposure ____
decreases
Destructive is a condition in which ____
there is an decrease in thickness, effective atmoic #, and/or density
destructive conditions ____ attenuation
decrease
as destructive disease worsens, IR exposure ____
increase
Which of these pathologies result in the increased attenuation of the beam
a. osteoporosis
b. emphysema
c. pneumothorax
d. congestive heart failure
D
Which of these pathologies result in the decreased attenuation of the beam
a. tuberculosis
b. pneumonia
c. cardiomegaly
d. emphysema
D
tuberculosis
additive
pneumothorax
destructive
atelectasis
additive
pagets disease
additive
emphysema
destructive
bowel obstruction
destructive
osteoporosis
destructive
What is being described:
highest actual atomic #
low effective #
low density
AIR
What is being described:
lowest effective #
low density
similar tissue to water
FAT
What is being described:
high actual atomic #
high effective #
higher density than FAT
MUSCLE
highest attenuator is ___
BONE
fat has tissue similar to ___
water
which one has higher density
a. muscle
b. fat
A
How can a technologist tell if an image is overexposed
a. the exposure indicator number will be out of range
b. loss of contrast
c. image show quantum mottle
d. image show saturation
A
what is dexel
Rounds average attenuation coefficient to nearest preset value in dynamic range
3 components of dexel
A-Se
TFT
Capacitor
A pixel corresponds to ___
area of pt’s tissue
pixel size depends on ____
matrix size
___ pixel size = more details
small
what is subset of bit depth
dynamic range
what is subset of dynamic range
grayscale
how to calculate # shade of grays
2^bit depth
large matrix size = ____ quality
high
voxel is collected by ___
dexel
The main image capture component of all dr detectors is the
a. Active matrix array
b. pixel
c. voxel
d. flat panel IR
A
AMA is main image capture of ____
a. DR
B. CR
DR
What made up of AMA (2)
flat panel & dexel
function of AMA
convert remnant xray to electrical signal
A cassette-based is used in ___
a. CR
b. DR
CR
IR type for DR & CR
DR: TFT
CR: PSP
function of PSP
stores xray energy as latent image
PSP is sensitive to ___
BG radiation
CR imaging plates use which of the following?
a. barium fluorohalide
b. amorphous silicon
c. amorphous selenium
d. barium sulfate
A
dexel material for direct capture
amorphous selenium
dexel material for indirect capture
amorphous silicon
xray strikes the scintillator in ___
a. direct capture
b. indirect capture
c. CR
B
which IR type has 7 layers
a. PSP
b. TFT
PSP
what is quantization
3rd step of digitizing images
level out brightness level for pixel to nearest gray available in preset dynamic range
Histogram shows ___
a. brightness value
b. grayscale.
brightness value
histogram has ____ that can recognize false densitities
light field recognition
Histogram analysis do 2 things: _____
compare histograms
eliminate data that skew with rescaling
5 histograms selection errors
▫Segmentation
▫Matching
▫Prosthetic & lead apron in collimated area
▫Pre-fogging of IR from BG radiation
▫Extreme scatter radiation
An image with appropriate spatial resolution could be said to have:___
a. sharpness
b. visibility
c. distortion
d. noise
e. quantum mottle
a. sharpness
The total number of pixel values that can be produced by the digital system is the ____
a. bit depth
b. dexel
c. exposure latitude
d. dynamic range
a. bit depth
The range of exposures that can be captured by a detector is the ____
a. dynamic range
b. grayscale
c. contrast
d. window level
a. dynamic range
The ability to produced quality images within a range of acceptable techniques is _____
a. exposure latitude
b. dynamic range
c. rescaling
d. DQE
a. exposure latitude
A graphic representation of the recorded signals received by the IR is known as
a. DR
b. histogram
c. rescaling
d. image sampling
Histogram
Spatial resolution is controlled by ___
a. bit size
b. mas
c. kvp
d. pixel size
a. bit size
Interpolation can fix ___
a. dead pixels
b. image ghosting
c. effects of scatter
d. segmentation errors
a. dead pixels
LUT gives _____
just right amount of brightness & contrast
adjustments to LUT
output pixels adjusted to same output Q values
LUT adjustments happened during____
image rescaling
4 steps to preprocessing?
- Field uniformity
- Dexel & noise correction
3.Histogram & analysis
4.Rescaling
field uniformity has this computer software called ____ that compensate areas out of range of uniformity
electronic amplification
Anode heel effect is partially compensated by ____
field uniformity
purpose of field uniformity
correct uneven distribution of BG density
What is segmentation failure
When individual exposure cant be separated
when will segmentation failure happen
CR
interpolation is ___
a. postprocessing
b. preprocessing
B
how does interpolation reduce noise
through software KERNEL
purpose of interpolation
give dead pixels the gray surrounding it
DQE stands for ___
detective quantum efficiency
purpose of DQE
measure the efficiency of IR in converting xray into radiographic image
DQE =1 means ___
100% of information is converted
increase DQE = ___ IR exposure AND ____
decrease
pt dose
which of the following provide ideal brightness & balanced grayscale regardless of technique
a. rescaling
b. field uniformity
c. LUT adjustment
RESCALING
process of rescaling
S –> Q –> placed in permanent LUT
amorphous selenium absorbs _____
a. xray
b. light
a. xray
amorphous silicon absorbs _____
a. xray
b. light
b. light
which phosphor is in scintillator layer for indirect capture
cesium iodide
what is the phosphorescent screen of indirect capture DR
scintillation layer
immediate light emission by some types of stimulation is ____
Fluorescence
delayed emission of light is ____
Phosphorescence
what is the second stimulation to phosphorescence
laser beam
latent image becomes ___ after exposure
manifest image
underexposure cause ____
quantum mottle
overexposure caused ____
saturation
windowing affects ___ of images
visibility
3 functions of PSP
- Ionize phosphors
- Trap e- & convert to electric signals
- Stores xray energy as latent image
exposure latitude controls ____
brightness & contrast
wide exposure latitude = ____
low contrast
narrow exposure latitude = ____
high contrast
what is exposure indicator number
indicate level of radiation exposure to IR
if out of exposure indicator range it will cause ____
NOISE
what is dynamic range
range of exposure intensities to IR
what is dynamic range compression
remove darkest to lightest pixel values from grayscale
DRC allows __
windowing
spatial domain operation is __
a. preprocessing
b. postprocessing
POSTPROCESSING
what is point processing
performs specific pixels in sequence
image substraction is an example of ___
a. point processing
b. area processing
c. global operations
A
what is area processing
Execute mathematical function on a subsection of image
magnification is an example of ___.
a. point processing
b. area processing
c. global operations
b. area processing
image orientation is an example of ____
a. point processing
b. area processing
c. global operations
c. global operations
with global operations, middle column is being ____ while corresponding columns are ____
translated
inverted
detail processing is in which domain operation
frequency
windowing is in which domain operation
intensity
high frequency = ____ pixel size
increase
high wavelength = ____ pixel size
decrease
what is submatrix
spatial detail processing with kernels
what allows frequency processing to separate structure
fourier transformation
4 postprocessing features of detail processing
- smoothing
- BG suppression
- local contrast of fine details
- edge enhancement
mid-size structures suppressed by contrast reduction & move into BG happened in ____
detail processing
pro and con of edge enhancement
Pro: increase local contrast for small pathology changes
Cons: increase image noise
if over enhance local contrast = ___
loss of details
BG suppression reduce contrast of ____ structures
larger mid-frequency and low-frequency
pro & con of BG suppression
Pros: effective in tissues like fat pads
Cons: Result is similar to edge enhancement
Smoothing removes ___ structures
highest-frequency
which 2 postprocessing features give the same result
BG suppression & edge enhancement
soft edge is due to ___
decrease in local contrast
noise is reduced by ___
interpolation
purpose of smoothing
corrects for dead pixels in IR + amount of mottle
severe mottle = ___
gross underexposure
Cons of smoothing
lose small details that contribute to diagnostic information
decoupling local contrast is ____
fine details visible
whole image has same contrast
if we eliminate noise, we need to accept the fact that
some fine details are gonna be lost
soft tissue technique can be stimulated by ___
DRC
adjust pixel values to fit average histogram & small exposure error is _____
rescaling
segmentation doesnt occur in ___
a. CR
b. DR
B.
what can correct quantum mottle
a. kernel
b. frequency filtering algorithm
c. none
kernel
what can correct electric mottle
a. kernel
b. frequency filtering algorithm
c. none
frequency filtering algorithm
What is imaging cycle in order
exposure –> histogram –> permanent LUT (rescaling) –> anatomical LUT (gradation) –> default detail processing –> displayed image
