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Review-Image A and E

Image acquisition and evaluation review

Density (brightness) amount of blackness on a given area of a radiograph
mAs controls what? quantity of xrays produced
kVp controls what? the energy or quality of xrays produced
Contrast differences in adjacent densities on the radiographic image
density may be defined as: darkness on a radiograph
the radiographic image is formed by: exit rays striking the image receptor
the primary controlling factors of density are: mAs and window level
How do you describe the relationship between mAs and density? density is directly proportional to mAs
the number of electrons boiled off the cathode and consequently the number of xrays produced are controlled by: mAs
the law stating that any combinations of mA and time that produce the same mAs value will produce the same radiographic density is the: reciprocity law
the active portion of a CR IP is: PSP
the primary controlling factors of contrast are: kVp and window width
the relationship between kVp and density may be described as: direct, although not proportional
the 15% rule states that: density may be halved be decreasing kVp by 15%
what governs the relationship between SID and density? inverse square law
if SID is doubled, what may be said about radiographic density? density is reduced to one-fourth
if SID is reduced by one-half, what must done to mAs to maintain a constant density? reduce mAs to one-fourth its original value
What can cause poor recorded detail? Long OID, Large focal spot, patient motion, magnification
in digital fluoroscopy, what equipment should be used to view the image? high-resolution monitor capable of displaying millions of pixels
a primary advantage to digital fluoroscopy is: postprocessing manipulation of the image
which of the following describes the relationship between radiographic density and the use of grids? grids reduce density unless mAs is increased to compensate
the use of filtration: has little effect on density because xrays removed from beam are not image producing rays
as beam restriction increase: density decrease
the variation of xray intensity along the longitudinal axis of the xray beam describes: anode heel effect
the thicker part of anatomy should be placed under which aspect of the xray tube? cathode
the function of contrast is to: make detail visible
a radiograph with few gray tones, primarily exhibiting black and white, would be described as having what type of contrast? high contrast, short scale
poorer recorded detail may be caused by which of the following factors? pixel pitch wide
high kVp produces which of the following? low contrast, long scale, many gray tones
low kVp produces which of the following? high contrast, short scale, few gray tones
more uniform penetration of anatomical structures occurs when what level of kVp is used? high
differential absorption of the xray beam is a function of: photoelectric interaction
What effect does beam restriction have on contrast? increase contrast because of reduction in the number of compton interactions that occur
the adjustment in technical factors required when using beam restriction is: increase mAs to compensate for the number of rays removed from the primary beam
what effect does the use of radiographic grids have on contrast? increase contrast
as the amount of beam filtration is increased: contrast decreases
the portion of contrast that is caused by variations in the anatomy or is secondary to pathological changes is called: subject contrast
recorded detail is: geometric representation of the part being radiographed
better recorded detail may be caused by what? long SID, short OID, small focal spot
optimal recorded detail may be created using what? narrow pixel pitch
elongation and foreshortening are examples of: shape distortion
magnification is caused by: short SID, long OID
distortion that occurs when the xray beam is angled against the long axis of a part is: foreshortening
distortion that occurs when the xray beam is angled along the long axis of a part is: elongation
the actual patient dose as measured by a meter embedded in the collimator is: dose area product (DAP)
quality assurance and maintenance of CR cassettes includes cleaning and inspecting the plates at least: every 3 months
quality assurance and maintenance of CR cassettes includes erasing plates at least: daily
quality assurance of digital imaging requires the uniformity of processing codes to ensure: image appearance consistency
a software function that evens the brightness displayed in the image called: smoothing
beam part receptor alignment latitude describes: the latitude of collimation that still allows the software to detect collimated edges
exposure technique in digital imaging may be adjusted by: increasing kVp
digital imaging is more sensitive to: scatter and background radiation
inappropriate collimation causes: histogram analysis error
an artificial increase in display contrast at an edge of the image is: edge enhancement
as speed class increases: the likelihood of noise increases
smoothing software may result in: loss of fine detail
excessive processing of the digital image may: degrade visibility of anatomy
a high SNR provides an image with: higher spatial resolution
quantum noise limits ability to see: detail
grid ratio is defined as: the ratio of the height of the lead strips over the distance between the lead strips
grid frequency is defined as: the amount of lead in the grid (expressed as the # of lead strips per inch)
a grid with lead strips and aluminum interspacers that are angled to coincide with the divergence of the xray beam is called a: focused grid
the range of SIDs that may be used with a focused grid is called: grid radius
the best scatter cleanup is achieved with the use of: crosshatch grids
grid cutoff may be described as: decreased density on a radiograph as a result of absorption of image forming rays
use of the air gap technique: works because scatter radiation travels in divergent paths and misses the IR as a result of increased OID
materials that make flat panel detectors possible are: amorphous silicon
Which of the following maintains image brightness over a wide range of exposures? automatic rescaling
the available gray scale of an imaging system is determined by: bit depth
the smallest exposure change able to be captured by a detector is called: contrast resolution
an indicator of the dose level needed to acquire an optimal image is: dose area product
the useful image acquisition area of an image receptor is: detector size
the smallest resolvable area in a digital imaging device is: detector element
what allows more anatomical structures to be captured during an exposure? dynamic range
the range of receptor exposures that provides a quality image is called: exposure latitude
which of the following is a graphical representation of pixel values? histogram
undesirable fluctuations in brightness are called: image noise
the number of pixels making up the digital image is the: matrix size
the expression of image quality provided by a detector is called: modulation transfer function (MTF)
which of the following terms describes the highest spatial frequency that can be recorded by a digital detector? nyquist frequency
what converts light into a charge? photodiode
the smallest area represented in a digital image is the: pixel
the number of pixels/mm in an image is called: pixel density
the space from the center of a pixel to the center of the adjacent pixel is called: pixel pitch
the process of assigning a value to each pixel to represent a gray tone is called: quantization
a material that absorbs xray energy and emits part of that energy as visible light is called: scintillator
bit depth is equal to: 2n (n equals the # of bits)
receptor exposure the amount of radiation striking the image receptor
30% rule to see a difference in density, the mAs must change at least 30%
filtration effect on contrast? increase filtration=lower contrast
collimation effect on contrast? increase collimation=increase contrast
units of spatial resolution? lines pairs per millimeter (lp/mm)
what technical factors should be used for wet plaster casts? increase 15 kVp
what technical factors should be used for dry plaster casts? increase 10 kVp
what technical factors should be used for fiberglass cast? increase 5 kVp
what technical factors should be used for iodinated contrast? not over 70 kVp
what technical factors should be used for barium contrast? not over 100 kVp
whats the order of film development? developer, fixer, wash, dry
where do most processor problems with film occur? developer
what temperature should the developer be? +/- 2 degrees of 95 F/ 35 C
the faster the speed of the screen? the greater the density
where is the micro switch located that controls replenishment near the entrance roller
collimation effect on density? increase collimation=decrease in density
how high is the safelight over the processor 36"
does mAs go up or down for a higher grid ratio? mAs goes up
mAs effect on density? increase mAs=increase density
kVp effect on density? increase kVp=increase density
SID effect on density? increase SID=decrease density
grid ratio effect on density? increase grid ratio=decrease density
filitration effect on density? increase filitration=decrease density
anode heel effect on density? increase anode heel effect=decrease density
patient factors effect on density? increase factors=decrease density
kVp effect on contrast? increase kvp=decrease contrast
OID effect on contrast? increase OID=increase contrast
grid ratio effect on contrast? increase grid ratio=increase contrast
patient factors on contrast? increase factors=decrease contrast
Created by: Chrslarsen