-
How many cycles of electricity occur in a second, 1/2 second?
60 cycles, 1/2 second 30
-
How many impulses of x-rays are generated per second, 1/2 second?
60, 30
-
What does the mA measure?
Quantity or amount
-
What 2 factors determine quantity of electrons thus x-rays?
mA and time
-
What control factor determines the speed of electrons thus the penetrating power of x-rays?
kVp
-
What does kVp measure?
Quality or speed
-
What control panel setting controls contrast?
kVp
-
A radiograph with mostly black and white is called a ______ contrast.
High scale or short scale
-
What produces a short scale (high scale contrast)?
low kVp
-
What produces a long scale (low scale contrast)?
High kVp
-
A radiograph with lots of grays is called a _____contast.
low scale or long scale
-
What is the step-down transformer controlled by?
mA
-
What is the step-down transformer connected to and heats up?
Filament wire (low voltage filament circuit)
-
What is the step-up transformer connected to?
mA and kVp
-
What is the step-up transformer controlled by?
kVp
-
Which transformer has more turns in the secondary coil?
Step-up
-
Which transformer has more turns in the primary coil?
Step-down
-
Which is the negatively charged terminal?
Cathode
-
Which is the positively charged terminal?
Anode
-
What two structures are made of Tungsten?
Target and filament wire
-
What is the source of electrons?
filament wire
-
What is the source of x-rays?
Target
-
What parts are inherent filtration?
Glass (aperature), Oil bath, and Metal barrier
-
What part is added filtration?
filter
-
Which 3 structures are protective devices?
filter, PID, and collimator
-
What does the filter do, what is it made of, and how thick does it have to be?
- Removes weak, less penetrating x-rays from the beam
- Aluminum
- 1.5 under 70 kVp and 2.5 70 and above
-
What does the collimator do, and what is it made of?
- Restricts the size of the beam to 2.75 inches
- Lead
-
Which PID reduces the radiation exposure the most and how much?
- long, lead lined, rectangular
- 50%
-
What two control panel factors settings control density?
mA and time
-
High density film is obtained by increasing the ___or ___.
mA or time
-
Low denstiy film is obtained by decreasing the ____or____.
mA or time
-
What must be present to produce x-rays?
- A source of free electrons
- A high voltage to give them speed
- A target to stop them
-
What happens when the low voltage circuit is activated?
The filament wire heats up and thermionic emission occurs
-
What happens when the high voltage circuit is activated?
- There is a potential difference between the cathode and anode
- Electrons are propelled towards the target
- X-rays and heat are produced
-
When are x-rays produced?
When electrons strike the tungsten target
-
How much is heat and how much is x-ray that is produced?
-
Define self-rectification
X-rays are only produced when the cathode is negative and the anode is positive
-
Define attenuation
The removal of x-rays from the beam by absorption or scatter
-
Radiopaque structures are a result of more or less attenuation of x-rays?
More
-
Radiolucent structures are a result of more or less attenuation of x-rays?
Less
-
Attenuation by absorption is?
Photoelectric effect
-
Attenuation by scatter is?
Compton effect
-
Define Bremstrallen radiation
When electrons interact with the nucleus of a target atom
-
Define Characteristic radiation
When electrons interact with an electron of a target atom
-
Define Thermionic emission
The boiling off of electrons into a cloud at the filament wire
-
Foreshortening
Too much vertical angulation
-
Overlapping
Error in horizontal angulation
-
Elongation
Not enough vertical angulation
-
#00 and 0 film
children PA and BW
-
#1 film
Adult anterior PA
-
#2 film
Adult posterior PA and BW
-
#3 film
Long adult posterior BW
-
#4 film
Occlusal, whole arches
-
Characteristics or Properties of X-rays?
- Can cause a fluorecent screen to glow
- Can affect a photographic plate
- Invisible
- Travel long distances at the speed of light (186,000 mi/sec)
- Have no mass
-
Advantages of paralleling and bisecting?
- Paralleling- less distortion
- Bisecting- good for shadow palates
-
Define Density and Contrast
- Density- overall blackness of the film
- Contrast- difference in densities within a film
-
Purpose of intensifying screen
To intensify the radiation to allow a reduction in radiation exposure time
-
Why use fast speed film?
To reduce exposure time
-
What is the fastest speed film and how much does it reduce exposure time?
-
To change from 10 mA and 6 seconds to 15 mA exposure time and maintain density?
- 10 X 6=60 mAs
- 15x = 60 mAs
- x = 4 seconds
|
|
