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RADR 2305, Chapters 26, 27, 28, 29, FINAL
Terms in this set (75)
What are the two photographic factors that allow detail to be seen?
Density & Contrast
What does window level control?
Doubling mAs will have what effect on density?
Density will double
If kVp is doubled, what happens to the intensity?
It is quadrupled
What is the relationship between window level and density?
Window level manipulation is done through _________________ or ___________________ of pixel values
Addition or subtraction
What is the typical OD range?
0.25 to 2.5
(or .5 to 2.0)
What is the controlling factor of density?
What does mAs reciprocity mean?
Several ways to get your mAs
Need a ____% minimum change in mAs to visualize a change in density.
A change in ________ results in a change in kinetic energy of electrons in tube.
Decreasing kVp by 1/2 will have what effect on intensity?
Will change intensity to 1/4th the original value
What are the types of generators?
How does FSS affect density?
It does not
How does focal spot blooming affect detail?
What is this effect called?
Focal spot blooming will
focal spot blur
- especially at edge)
What does blooming do to focal spot?
Density up to ______% greater at cathode side of beam
What is the inverse square law?
Double SID = intensity will decrease by a factor of 4 (or will decrease to 1/4th)
What is the density maintenance formula?
Increased filtration will have what effect on density?
Low energy = ______ wavelength
low energy = long wavelength
Increasing the angle has what effect on density?
Decrease density because it is increasing SID
What is grid conversion formula?
How is film screen related to density?
When does development fog happen?
When development of unexposed silver halide crystals occurs
What are the two geometric factors?
Detail & distortion
Window width has what kind of relationship to contrast?
What is short scale contrast?
Change in D log E curve of film will affect what?
Radiographic contrast = ___________ x ___________
Radiographic contrast = subject contrast x IR contrast
Subject contrast is affected by what factors?
Subject contrast affected by
-density/thickness of tissue,
-concentration of tissue,
-atomic number of tissue,
IR contrast is affected by what?
IR contrast affected by
-size of crystals,
-type of matrix system,
What are the 4 factors that determine contrast - film?
1. Intensifying screen
2. Film density
3. Slope of D log E curve
Which has lower contrast, directly exposed film or screen film?
Directly exposed film has lower contrast than screen film
The use of intensifying screens has what effect on contrast?
Two lines on D log E curve - which one has faster film speed?
Subject contrast is dependent on what 3 things?
2. Amount of irradiated material
3. Type of irradiated material
Increase in thickness and field size have what effect on contrast?
Longer scale of contrast
High atomic number and tissue density have what effect on attenuation?
Do not exceed ____ kVp for nongrid
What is the controlling factor of contrast?
Increasing grid ratio has what effect on contrast?
Use of intensifying screen has what effect of contrast?
How do the following affect contrast?
+ mAs = no effect
+ SID = no effect
+ OID = + contrast (air gap)
+ Part thickness = - contrast (+scatter)
FSS has what effect on contrast?
Beam restriction has what effect on contrast?
More collimation = less scatter = higher contrast
Number of photons is greater on which side of the X-ray tube?
Absorption of x-ray by heel of anode is called what?
anode heel effect
Increased filtration has what effect on contrast?
Increase in bit depth has what effect on contrast?
Decrease in contrast
Increase in shades of grey
(higher dynamic range)
Which type of distortion is described as "true distortion?"
What is another name for penumbra?
Focal spot blur
What is the equation for Focal Spot Blur?
FSB = FSS x OID/SOD
As FSS increases, what happens to focal spot blur?
What are PSF, ESF, & LSF?
Point spread function, Edge spread function, & Line spread function
(All of these describe the blurring of the point of line or edge - boundary blurring)
What is the equation for MTF?
MTF = Image/object
(A perfect MTF is 1)
Modulation Transfer Function
What are some variables of MTF?
IR, post processing, monitor, etc
The ability of an imaging system to accurately display objects in two dimensions is called what?
What is the Nyquist Criterion?
Frequency signal must be sampled twice per cycle
When the signal is sampled twice per cycle, then one would say it is meeting nyquist criteria
What is the Aliasing (Moire effect)?
-Occurs when Nyquist Criterion is not met
-Low-frequency image wraps around high-frequency image
-Visual appearance of two images slightly out of alignment
What are the layers of an intensifying screen?
How does the presence of the reflective layer affect resolution?
How does the presence of x-ray absorbing dye affect resolution?
Increases resolution by decreasing the spread of light
What are the phosphors?
Factors affecting recorded detail
Focal spot size
Intensifying screen phosphor size & concentration
(the spread of light causes blur and fog and reduces resolution)
What is fill factor?
Percent of the pixel that is sensitive to the x-rays
Indirect DR components
(ccd = charge coupled device)
Direct DR components
A semiconductor that senses light and converts to electrical charge
Charged coupled device (CCD)
In digital systems, recorded detail is dependent on what three things?
1. Acquisition and display matrix
2. Pixel size
3. Grayscale bit depth
Factors affecting distortion
What things affect shape distortion?
1. CR direction
3. Relationship between body part and IR
What is the equation for Magnification Factor?
Magnification factor = image size/object size
MF = SID/SOD
SID/SOD = image size/object size
SID - OID = SOD
If CR is centered to wrist for a forearm, which portion would be elongated and which foreshortened?
superior forearm = elongated
wrist = foreshortened
What 2 factors affect shape distortion?
(Central ray, Anatomical part, Image receptor)
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