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54 Cards in this Set

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Overall aomount of blackening on film?
Density
What is density rate regulated by?
exposure rate or nmber of photons reaching the film
To graphically illustrate the response of x ray film to amounts of exposure the densities can be plotted on a graph. What is this called?
H&D Curve, sensitometric curve, or characteristic curve.
Radiographic film base plus fog ranges around what numbers?
.05-1.0
What is the diagnostic useful range of density?
.25-2.5
The study of film emulsion to exposure is what?
sensitometry
What does the study of sensitometry require the use of?
sensitometer, densitometer, and processor.
Difference in density represent what?
contrast
Product of ma and time
mAs
Any combination of mA and time that will produce a given mAs will produce an identical density. This is know as what?
reciprocity
Is mAs a quatitative factor?
yes
What does mAs regulate?
beam intensity
exposure rate
quantity or # of x rays
Is MAS directly or indirectly proportional to denisty?
directly
What do you do that produces more high energy x-ray photons?
Increase the kvp
KVP affects ___________ and ___________
of the film
quatity, quantity
How are kvp and mAs related?
directly but not proportionally
When mAs manipulation is not possible, how can you double or half the density and what is the disadvantage of doing this?
15% rule, you change the scale of contrast
The relationship between SID and density is governed by what law?
The inverse square law

I1 D2 squared
---=___________
I2 D1 squared
What is the distance maintenance formula?
mas1 (D1)2
____=_____
mas2 (D2)2
If 25 mAs at 40 inches is necessary how much mAs should be used if 72 inches must be used?
Distance Maintenance Formula
What is the purpose of an intensifying screen?
decrease patient dose and increase tube life
As screen speed increases what will patient dose do?
Decrease
The flourescent light emitted by the phospors is responsible for what percentage of image density?
98-99%
What is the purpose of a grid?
improve contrast
The primary purpose of a grid is to absorb _________ produced by what effect?
scatter, compton
The grid should be placed where?
Between patient and film
What should a patient measure for you to use a grid?
9-11 cm
What are the types of grids?
Stationary- grid lines
Moving
Parallel
Focused
Cross hatch-prohibit tube angulation
What are the types of grid errors?
Off-level-loss of density
Off-center-loss of density
Off-focus-dark strip down middle
Upside down grid-dark strip down middle
"Moire" artifact-2 focused grids on top of each other.
What are the grid ratio conversions?
5:1 2
6:1 3
8:1 4
10:1 5
12:1 5
16:1 6
What is grid ratio?

Grid frequency?
height/distance

# of lead strips per inch
Ordinary filtration of 2.5 mm Al has what effect on density?
none
What effect does beam restriction have on density?
decreases (4x4 and lower, only manual settings)
Does beam restriction have a greater effect on contrast or density?
contrast increases
Under manual technique how would you compensate for most additive pathology?
What would you do with AEC?
increase 5-15%, nothing automatically adjust
Is abscess additive or subtractive?
additive
Is edema additive or subtractive?
additive
Are tumors additive or subtractive?
additive
Is atealeactasis additive or subtractive?
additive
Is CHF additive or subtractive?
additive
Are pleural effusions additive or subtractive?
additive
Is pneumonia additive or subtractive?
additive
Is TB additive or subtractive?
additive
IS ascites additive or subtractive?
additive
Is cirrhosis additive or subtractive?
additive
Osteomyelitis is additive or subtractive?
additive
Is pagets's disease additive or subtractive?
additive
Is atrophy additive or subtractive?
subtractive
IS bowel obstruction additive or subtractive?
subtractive
is degenerative arthritis additive or subtractive?
subtractive
Is multiple myeloma additive or subtractive?
subtractive
Is osteomalacia additive or subtractive?
subtractive
Is osteoporosis additive or subtractive?
subtractive
Is emhysema additive or subtractive?
subtractive