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Exposure FINAL review

Terms in this set (61)

Identify 3 components of a radiographic image:
-density
-contrast
-recorded detail (geometric factors)
What are the grid conversation factors?
Non grid = 1
5:1 = 2
6:1 = 3
8:1 = 4
10:1 = 5
12:1 = 5
16:1 = 6
A radiograph is taken with a slow (RS = 50) screen, using 40 mAs at 80 kVp. If a rare earth (RS= 400) screen was substituted, what new mAs could be used to maintain a similar radiographic density?
mAs1 = RS2
mAs2 = RS1

40 = 400
x = 50

400x = 2000
400 = 400

x= 5 mAs
Define radiographic density:
-the degree of blackening on the film
-(caused by deposition of black metallic silver)
Explain the different between short and long scale contrast:
short scale contrast = a lot of difference between adjacent shades of gray

long scale contrast = very little different between adjacent shades of gray
Rank body tissues according to ability to absorb x-rays:
-Air
-Fat
-Muscle
-Bone
List 2 technical factors affecting sharpness of detail:
-SID
-OID
-Focal spot size
The controlling factor of density in film/screen imaging is:
mAs
Name the four things that can happen as x-rays are transmitted through the body:
-interact with patient and scatter away from the receptor
-interact and are absorbed (photoelectric absorption) within the patient
-transmitted through the patient without interaction and strike the receptor
-interact with the patient (Compton scatter) and scatter towards the receptor
The controlling factor of contrast in film/screen imaging is:
kVp
The conversion of the invisible latent image into a manifest image (in film/screen) takes place in the:
Developer
Of the following group of exposure factors, which will produce the greatest radiographic density?

a. 200 mA, 0.03 s 72" SID
b. 100 mA, 0.03 s, 36" SID
c. 100 mA, 0.06 s, 36" SID
d. 200 mS, 0.06 s, 72" SID
c. 100 mA, 0.06 s, 36" SID
The ______ focal spot is the area of the target actually being bombarded by electrons.
Actual
According to the line focus principle, the effective focal spot size is controlled by 2 things. What are they?
-size of actual focal spot
-anode target angle
The layers of film emulsion are:
-Base
-Adhesive
-Emulsion
-Supercoat
As kVp increases, ______ interactions increase.
Compton
Describe the conditions under which x-ray film should be stored:
-on end
-below 68 degrees
-30 - 60% humidity
-dark
-no radiation
As Compton interactions increase, ______ increases.
scatter
Radiographic contrast is a result of:
-differential tissue absorption
-emulsion characteristics
Which methods of limiting the production of scattered radiation?
-using the prone position for abdominal exams
-restricting the field size to the smallest practical size
Decreasing the field size from 14 x 17 in to 8 x 10 in will:
Will decrease density and decrease amount of scattered radiation created within the part.
Filtration primarily affect the dose to the patient's:
skin
A grid usually employed in which circumstances?
-when radiographing a large dense body part
-when using a high kilovoltage
Exposure factors of 90 kVp and 4 mAs are used for a particular non-grid exposure. what should be the new mAs if an 8:1 grid is added?
grid1 = mAs1
grid2 = mAs2

1 = 4
4 = x

16 mAs
Inherent filtration includes:
-glass envelope
-dielectric oil bath
- glass window of housing
In film/screen imaging, quantum mottle is most obvious when using:
Rare earth screens
Spatial resolution is messed by:
Line pairs per millimeter
Misalignment of the tube-part relationship results in:
shape distortion
What has an effect i recorded detail?
-focal spot size
-SID
______ conditions can usually be compensated by adjusting mAs.
Destructive
How does decreasing kVp affect the scale of contrast?
Shorter scale of contrast
The line focus principle expresses the relationship between:
The actual and effective focal spot
The factors that increase the anode heel effect are:
-short SID
-large film size
-small focal spot size
The function of the fixer in film processing is to:
remove the unexposed silver bromide crystals and harden the emulsion
Materials that emit light when stimulated by x-ray photons are called:
Phosphors
Name 2 ways to reduce scatter racing the film:
-restrict the beam
-use a grid
The term spectral matching refers to the fact that film sensitivity mist be matched with the:
color of light emitted by intensifying screen phosphor
How many shutters are in the tube housing
2

(upper = off focus radiation
lower = penumbra)
The lower set of shutters reduces the ______.
penumbra
Describe off focus radiation:
Off-focus radiation produces images beyond exposed field of radiation
What is the correct order of radiographic film processing
-Developer
-Fixer
-Washer
-Dryer
A compensating filter is used to
Even out widely differing tissue densities
The number of x-ray photons delivered to the patient in a given exposure is primarily regulated by:
mAs
For x-ray tubes operating above 70 kVp the minimum filtration (in mm pf Al equivalence) is:
2.5 mm Al eq
A change from 100 speed screens to 200 speed screens would require what change in mAs?
mAs should be cut in half
What is the best way to reduce magnification distortion?
Reduce OID
The reduction in x-ray photo intensity as the photon passes through material is termed:
Attenuation
The primary source of scattered radiation
Patient
Screen speed is affected by:
-conversion efficiency
-number of phosphor crystals
-phosphor type
The intensity of radiation is 6 mR/hour at a distance of 15 feet from the source. What would the intensity be 5 feet from the source?
54 mR/hr
Define filtration:
Process of eliminating undesirable low energy x-ray photons by insertion of absorbing materials into primary beam
Filtration is often referred to as ______ the beam
hardening
Filtration needed to reduce beam to one half of its original intensity is the definition of:
Half Value Layer (HVL)
The quality of the x-ray beam indicates the ______ and ______ of the photons.
energy and penetrability
Changing the kVp will change the _____ of the electrons crossing the x-ray tube.
speed
While kVp is the primary controller of beam quality, it also has a slight effect on ______.
Quantity
Because kVp affects both quality and quantity, a change of only ______ is needed to double the exposure to the image receptor.
15%
Increasing the kVp will _____ bream penetrability.
increase
Name 3 types of grids:
-parallel
-focused
-crosshatched
Name 2 types of grid movement
-Reciprocating
-Oscillating
Name 5 grid errors:
-off focus
-off level
-upside down
-off center
-moire
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