review Flashcards
the overall blackening of the film
density
the difference in adjacent densities on a radiograph
contrast
the main controller of density
mAs
the main controller of contrast
LUT
the quantity of x rays in the beam
mAs
the quality of x rays in the beam
kVp
causes image to appear larger than the object being radiographed , misrepresentation of the true size of the image
size distortion
the major factor in magnification
OID
decreases the effect of magnification
SID
distance is ______ proportional to density
indirectly
if distance is increased _____ must increase to maintain density
mAs
the two types of shape distortion are:
elongation & foreshortening
____ distortion is the misrepresentation of the true shape of the image as compared to the object
shape
occurs when the object is at an angle and the central ray is perpendicular to the film
foreshortening
occurs when the object is parallel to the film but the central ray is angled or if the central ray is perpendicular to the object but the object is not parallel to the film
elongation
changes in the tube always cause _____ NOT ______
elongation , foreshortening
the _____ _____ of the anatomical part / object is intended to be positioned perpendicular to the CR and parallel to the IR
long axis
a ____ focal spot improves recorded detail
small
____ time reduces the chance of motion blur
short
example of breathing technique
low mA , high time (25-50 mA, 2-3 s)
high kVp =
high photon energy
low contrast
long scale
low kVp =
low photon energy
high contrast
short scale
what radiographic color would bone have
white
what radiographic color would air have
black
high kVp = ____ scatter
higher
how does scattered radiation affect contrast
decreases contrast
if kVp is increased by 15% , mAs should be
halved
if kVp is decreased by 15% , mAs should be
doubled
why is 15% rule applied
to maintain exposure
high contrast is ___ scale
short
long scale = ___ contrast
low
_____ radiation passes through a grid
primary
_____ radiation is absorbed by the grid
scatter
the height of the lead strips compared to the distance between the lead strips
grid ratio
the number of grid lines per inch
grid frequency
a ___ grid ratio absorbs more scatter than a ____ grid ratio
high, low
unwanted absorption of primary radiation by the grid
grid cut off
the physical area of the focal tract that is impacted by the electron beam
the focal spot
a small ___ produces better recorded detail
OID
the sharpness of the lines of an image
detail
wedge and trough are examples of
added filtration
filtration located under the window between the x ray tube and the collimator
added
filtration present because of the design of the x ray tube
inherent
filtration _____ the average energy of the beam
decreases or increases
decreases
CR uses ___________ imaging plates inside a cassette
photostimulable storage phosphor (PSP)
a device used to convert incoming x ray photons to light
scintillator
a device used to convert light into an electronic signal
photodetector
small groups of pixels are called
kernels
processing operation that applies to small groups of pixels
local processing
processing operation that involves the adjustment of a pixel
point processing
point processing operation that allows for adjustment in brightness & contrast
windowing
digital imaging systems having a high signal to noise ratio has _____ quality
better
does an 8 bit or 16 bit system have more shades of gray
16 bit
determines the number of shades of gray that can be represented on an image
gray scale bit depth
in a CCD system what is responsible for focusing the light on to the CCD chip
fiber optics
CCD are ____ imaging
indirect
the process for indirect radiography
2 step process
direct radiography is a ____ process
1 step
what type of laser is utilized in PSP reader
helium neon
what is a translation movement
slow scan
single laser , reads raster pattern
point scan reader
reads entire line at a time
line scan
processing operation that involves the adjustment of a pixel
point processing
a histogram modification or stretching
rescaling
spatial resolution is determined by what 4 things?
pixel size
pixel pitch
matrix size
FOV
is the measurement of sensitivity and accuracy of an image receptor
DQE
indicates the amount of x ray exposure that reaches the IR
exposure indicator
small or large focal spot to decrease motion
large
the comparison between the actual exposure and the proper exposure received by the IR
deviation index
in PSP systems the active layer is
the phosphor
encompass BMI platforms used in health care facilities and in radiology departments, respectively
RIS & HIS
radiology & hospital information system
are the electronic version of an individuals patients collection of medical documents
EMR & EHR
a BMI platform configured for storing , archiving, and distributing medical images
PACS
the universal , standardized public format and protocol for communicating biomedical imaging files
DICOM
what will give the best detail - pixel size and pitch
small pixel size & small pixel pitch
what combination of FOVs and matrix sizes will provide best resolution
FOV of 12 & matrix size of 2045
small & large
the ____ the matrix , the better the resolution
larger
the volume of tissue seen in each pixel is
voxel
the ____ the pixel pitch the better the resolution
smaller
controls the lightness and darkness of an image on the display
window level
is the columns and rows of pixels
matrix
is the graphic representation of the IR exposure
histogram
how is contrast range of an image determined in CR & DR imaging
LUT - look up table
the mathematical algorithm called that sets the standard for contrast for the selected exam
LUT
the post processing function that increases contrast and enhances the edges of an image is known as
high pass filtering
removes high frequency noise and reduces contrast - post processing
low pass filtering
not enough photons hitting the IR during an exposure , the image will have
quantum mottle - repeat increase mAs
if an exposure was made at 85 kVp and the resultant radiograph did not have enough contrast , but the IE was good , what should be done on the repeat image
lower kVp
the effective focal spot is always smaller than the ___ when the angle is 45 degrees
actual
line focus principal theory
what does the term dual focus mean
tube has 2 filaments
according to the anode heel effect the intensity of the beam is greatest at the ____ end
cathode
photons not produced at the focal spot are known as what type of radiation
off focus
the total filtration required for an x ray machine above 70 kVp is
2.5 mm
tech dose comes from
compton interactions
patient dose comes from
photoelectric interactions
as kVp increases photoelectric interactions
decrease
as kVp increases compton interactions
increase
the geometric unsharpness around the edge of an image is called
penumbra
artifact that occurs when the digital imaging receptor captures the grid lines when scanning
moire effect
the main purpose of exposure systems
produce consistent images
amount of exposure needed to reach IR for an adequate exposure
1mR/ hr
the mathematical algorithm that changes an image from spatial location to spatial frequency domain
fourier transformation
occurs when the computer processing software eliminates data irrelevant to the exam
data clipping
is the information important to the exam in a digital image
FOV
the sensing area of a DEL is determined by the
fill factor
the greater the sensing area the ____ the resolution
better
use the ____ within the grids focal range to avoid grid cut off
distance
to avoid grid cut off do not angle the CR ____ the grid lines
against
to avoid grid cut off the beam and the grid must be ______ to each other
perpendicular
a _____ beam size reduces scattered radiation
small
a filter absorbs ___ energy photons
high
filtration does what to density and contrast
decreases both
filtration ______ the average energy of the beam
decreases
to increase the amount of contrast on a image pre exposure you would
decrease kVp
an increase in focal spot size will have what result in IR exposure
has no effect
if the mA is increased from 300 to 400 all other factors remain the same. what will happen to IR exposure
increase
which contrast scale is produced with a high kVp
long scale
which one of these body components would display the most radiographic (radiolucent) density
air
the lack of sufficient data reaching the IR is called
quantum noise
which beam would penetrate through body tissues easily
a beam produced with high kVp
which type of image would be produced on a radiograph with low kVp
high contrast
T/F: low kVp produces a short scale of contrast
true
anther term for the presence of scattered radiation in the film is
fog
high kVp produces a ____ scale of contrast
long
as beam restriction increases, contrast
increases
digital processing function that controls contrast
window width
the addition of filtration will _____ IR exposure
decrease
the utilization of strict collimation will ___ exposure
decrease
as distance is decreased , IR exposure will
increase
the anode heel effect will cause an increase in density at the ____ of primary beam of the part being imaged is equal thickness
cathode
additive pathology will ______ IR exposure
decrease
if a digital processing system is said to have a “high margin of error” or “wide dynamic range” then the tech can have
varying exposures
the grayscale bit depth determines the
contrast a system can display
when a high kVp is utilized for an abdominal radiograph it will result in a ______ scale of contrast
long scale
the ability of an IR to distinguish between objects is its
contrast resolution
T/F: proper contrast on an image can be determined by IR exposure
false
T/F: the addition of contrast media will decrease contrast
false
how do grids effect contrast
increase contrast
term to describe when the histogram automatically modifies the values of interest so they properly represent the anatomical part being imaged
rescaling
this occurs when an image is obtained that does not fit the parameters that were used in the reference histogram
histogram analysis error
when x ray photons are converted to light then light photons are converted to an electrical signal describes what type of system
indirect conversion
amorphous silicon is used in what system
indirect digital
amorphous selenium is used in what system
direct digital
which of the processing operations is utilized to change the position or orientation is pixels
geometric processing
the three dimensional data with the digital image
voxel
which of the processing operations includes high pass & low pass filtering
local processing
T/F : the greater the DEL the greater the resolution
false
when a PSP plate is flooded with intense light, the process is called
erasure
which of the following is utilized to convert analog data into a direct signal in a CR system before the computer can work with the image
ADC
when radiographers view images, they are represented in which domain
spatial location
in a PSP system ___% of the latent image will be lost in 8 hours if it is not processed
25%
in a PSP system , what is the active component that traps electrons during exposure
phosphor crystal
a pixel that has an eight bit depth displays _____ shades of gray
256
when matrix size is increased and pixel size goes down
spatial resolution increases
a line pair of a resolution grid is utilized to measure which of the following
spatial resolution
an increase in source image distance causes recorded detail to
increase
as resolution increases
recorded detail increases
edge enhancement is also known as
high pass filtering
increased background information will increase
image noise
M=
SID/SOD
minification
cannot be archived in radiography
placing the object parallel to the film will avoid
shape distortion
SID =
SOD + OID
SNR measures
noise
spatial resolution is best measured in which of the following situations
high contrast and small structures
temporal resolution is the ability of a system to
provide better resolution when motion is present
the point spread function is used to measure
detail
the ability of an imaging system to record two adjacent structures as seperate structures is called
recorded detail
the larger the pixel size the ___ the recorded detail
less
the number of lines per millimeter seen or able to be seen on an image describes :
spatial frequency
the processing algorithm that averages incoming analog data ( data is sampled twice )
nyquist criterion
using a short OID will avoid
size distortion
when incoming data is sampled less than twice this can occur
aliasing
____ expresses the edges of an image in digital imaging
PSF
___ measures the accuracy of an image compared to the original object
MTF
reticulation means
quantum mottle
what technique chart doubles or halves the mAs in increments of 30% for 5 cm changes in subject thickness
fixed kVp
what technique chart is consistent with the 15% rule
variable kVp
what is known as excessive signal to the IR
detector saturation
what technique chart utilizes 2kvp, part thickness and a base kVp to figure technique
variable kVp
