Test #2 Flashcards
Which of the five interactions with matter discussed in class are important in diagnostic level radiography?
Compton Effect and Photoelectric Effect
Which x-ray interaction with matter is more likely to occur with high atomic number tissues?
Photoelectric Absorption
Which x-ray interaction with matter is related to the energy of the x-ray photon?
Compton - increasing energy, increases the probability of it occurring. It is totally independent of atomic number of the material it is interacting with.
Photoelectric - decreasing KVP increases the probability of it occurring.
Classical - decreasing energy will lead to increase in probability.
Which x-ray interaction is the most likely to occur at energies below 10 keV?
Coherent Scatter
Which x-ray interaction with matter is most likely to occur at energies between 10-60 keV?
Photoelectric Absorption
Which x-ray interaction with matter is most likely to occur at energies greater than 60 keV?
Compton Scatter
Which shell level is ionized in the photoelectric absorption interaction?
Inner Shell
What happens to the original x-ray following the photoelectric interaction?
It is totally absorbed
Resulting in the bright areas on the radiograph
Which shell level is ionized in the Compton scatter interaction with matter?
Outer Shell
What happens to the original x-ray following the Compton scatter interaction?
Goes on to other reactions and creates fog.
What happens to the original x-ray following the Coherent scatter interaction?
There is a change in direction but no change in energy, therefore no ionization.
State three other names for the Coherent scatter interaction:
Rayliegh, Thompson, and Classical
State at least 2 advantages of tissue compression
It decreases the number of atoms in the path of the travel of the x-ray.
Decreased patient thickness = Decreased Compton Scatter
State at least 2 advantages of performing PA lumbar spine examinations instead of AP
It decreases radiation dose to the gonadal region
Decreases scatter
Improves detail
How does collimation to the film size or smaller effect the production of scatter radiation?
As the collimated field size decreases, compton scatter interactions also decrease (less atom at the path of travel).
How does collimation to the smallest field size possible effect radiographic contrast?
Increasing film size reduces scatter radiation.
When collimating down “significantly”, what must be done to maintain radiographic density?
mAs must be increased by 50%
How does kVp effect the production of scatter radiation?
Compton scatter interaction increases as kVp increases.
The ideal is no scatter
Scatter leads to poor contrast, fog, dull film
Increasing kVp will give long scale of contrast and thus lots of shades of gray
or every 4cm of tissue thickness increase mAs should be doubled.
True or False
True
State 2 AKA’s for SID?
FFD and TFD
State the inverse square law formula:
Inversely Proportional (old/new = new2/old2)
Density SID Equation
Directly Proportional (old/new = old2/new2)
The exposure rate 3 feet from a source of radiation is 40mR per hour. What is the exposure rate at 6 feet?
x = 9
40 = 36
(9/36) x 40 = 10
The exposure rate 3 feet from a source of radiation is 40mR per hour. What is the exposure rate at 12 feet?
2.5
A lumbar spine radiograph requires 30 mAs at 40” SID. What mAs will be required to achieve the same radiographic density if the SID is changed to 80”?
120 mAs
A cervical spine radiograph requires 12 mAs at 72” SID. What mAs is required to achieve the same radiographic density if the SID is changed to 40”?
3.7 mAs
What is the purpose of radiographic “Bucky” grid?
Reduce Compton Scatter
When is it necessary to use a grid?
> 10 cm Thickness
> 60kVp
What is the advantage of a high frequency grid?
Decreased line visibility
No need for a moving grid mechanism
Height of lead strips divided by width of lead strips is called?
Grid Ratio
What type of chiropractic practice would require a relatively high grid ratio?
Gonstead
There are 3 types of grids - name them
Parallel Linear, Crosshatch, Focused Linear
Why would you not want to purchase a crosshatch grid?
You can’t angle the central ray
Define grid radius
Proper SID range, Focal range proper focal range
Describe a radiograph taken at the improper grid radius.
THERE WILL BE LATERAL CUT-OFF ON BOTH EDGES
Define grid cutoff.
underexposed
grid frequency
OF GRID STRIPS PER CM OR INCH
State the three types grid movement.
OSCILLATING, RECIPROCATING, SINGLE STROKE/MANUALLY COCKED
What type of chiropractic practice would require a relatively low grid ratio?
upper cervical
Is a grid a radiation protection device - for the patient?
No
Which ratio grid would require the greatest increase in exposure?
HIGHER GRID RATIO= HIGHER mAs
Describe a radiograph that is taken with the central ray off center.
PRIMARY X-RAYS COLLIDE WITH STRIPS->GRID CUT OFF ON LATERAL EDGES
Describe a radiograph that is taken with the beam angled to the left or the right
CUT-OFF ON ONE LATERAL EDGE
Why are intensifying screens used with x-ray film
VISIBLE LIGHT FROM INTENSIFYING SCREENS PRODUCE THE IMAGE BY STIMULATING SILVER HALIDE ON FILM
What is the film base made of
PLASTIC/MYLZA
Why does a double-coated film emulsion result in a decrease in sharpness
THE FASTER THE FILM OR SCREEN THE THICKER THE EMULSION, LIGHT DIVERGES OVER EMULSION PRODUCING PENUMBRA
Define latent image:
THE IMAGE ON THE FILM PRODUCED BY THE RARE EARTH CRYSTALS THAT IS NOT YET DEVELOPED
Define manifest image:
IMAGE ACTUALLY SEEN ON FILM AFTER PROCESSING
How is film manufactured to increase its’ speed
INCREASE THICKNESS=INCREASE SPEED
Which of these imaging systems would you choose if you were imaging extremities, 100, 600, 1200?
100
Which of these imaging systems would result in the most radiation exposure to the patient? 100, 600, 1200
100
Which of these imaging systems would result in the least radiation exposure to the patient, 100, 600, 1200?
1200 speed
Which of these imaging systems is the most consistent with the ALARA concept, 100, 600, 1200?
1200
What is the cause of quantum mottle, what does it look like?
CAUSED BY DECREASED X-RAYS USED TO PRODUCE THE IMAGE. LOOKS GRAINY LIKE A LOW MEGAPIXEL CAMERA PIC
Which of these imaging systems would result in a radiograph with the most quantum mottle, 100, 600, 1200?
1200
What is the lowest film-screen system speed that you should consider using for routine spinal radiographs
400 speed
What does the term film latitude mean
THE ABILITY OF THE FILM SCREEN SYSTEM TO ALLOW FOR ERROR, (LONG LATITUDE IS MORE FORGIVING), WIDE RANGE OF USEFUL DENSITIES
How is film contrast related to film latitude
AS FILM LATITUDE INCREASES, FILM CONTRAST DECREASES, INVERSELY RELATED
What color safelight is safe to use with both green and blue sensitive film(univeral)
RED, GBX SAFELIGHT
How far away from the work surface should a safelight be hung
4 feet
How do you know that the safelight filter is installed properly
WRITING IS ON THE OUTSIDE AND READ LEFT TO RIGHT
What is the maximum wattage of a light bulb for the safelight
WHAT THE MANUFACTURER SAYS OR 15 WATTS OR LESS
What color of light do rare earth screens emit, what type of film must be used with them
green yellow, green sensitive film
What color of light must the intensifying screen emit for orthochromatic film to respond
green
What color of light do calcium tungstate screens emit, what type of film must be used with them?
BLUE VIOLET, BLUE SENSITIVE FILM
If a technique is based on 200 speed imaging system and requires 30 mAs, 80 kVp, 40” SID, what must be done to compensate if a new 600-speed system is used
USE 1/3 mAs=10 mAs
When an artifact is demonstrated on a film as a result of something on the screen, what color will it appear. will it be sharp or blurred? why?
WHITE, SHARP DEBRIS BLOCKING LIGHT FROM INTENSIFYING SCREENS
What should be used to clean an intensifying screen
SCREEN CLEANER AND LINT FREE GAUZE
What temperature and humidity should film be stored at
68 DEG AND 40-60% HUMIDITY
Where is the film’s expiration date located? what is the result of using film that is out of date?
ON THE BOX INCREASE FOG, DECREASE CONTRAST…BREAK DOWN OF SILVER HALIDE CRYSTALS
What may appear on the film if the humidity is too low
BLACK ARTIFACTS FROM STATIC
Why is the use of “split screens” considered obsolete
REQUIRES TOO MUCH EXPOSURE
What should be done instead of using “split screens” why is this consistent with the concept of ALARA?
use filter, decreases patient exposure
What is film emulsion made of?
SILVER HALIDE CRYSTALS SUSPENDED IN GELATIN
This processing solution is alkaline
developer
This processing solution is acidic
fixer
This processing chemistry must be passed through a device to reclaim silver
fixer
This processing solution consists of a reducing agent, activator, restrainer and preservative
developer
What is the difference between automatic and manual processing developer
NO HARDENER IN MANUAL
In manual processing where is the hardener found
fixer
In automatic processing chemistry, where is the hardener found
IN DEVELOPER AND FIXER
State the standard time-temperature for manual processing
5 MIN AT 68 DEG (64-72)
You are performing manual processing. The developer temperature is 66 degrees Fahrenheit. How long should the film be developed
5 MIN 30 SEC ADD 15 SEC PER DEG DIFF
What does exhausted developer look like
motor oil
Describe how developer should be mixed
A->B->C->D PREVENTS DEVELOPER FROM OXIDIZING
Why is there a floating lid on the developer replenisher chemistry
TO PREVENT OXIDATION OF CHEMICALS
Why is the processor lid left open when the processor is off
TO PREVENT CONDENSATION FROM BUILDING UP/PREVENTS CONTAMINATION
Why is the water tank in the processor drained when it is off
KEEPS ALGAE OUT OF TANK
Describe how and when crossover rollers should be cleaned
EVERYNIGHT WITH WATER AND SYNTHETIC SPONGE, ONE COLOR FOR FIXER AND ANOTHER COLOR FOR DEVELOPER
How often should the entire processor be drained, cleaned and replenished
MONTHLY (4-6 WEEKS, DOCUMENTED AND POSTED) Costs roughly $100
per clean up
Which edge of the processor feed tray should be used and why
ALTERNATE TO AVOID OVERUSE OF MICROSWITCH
Why does the direction of film transport through the processor matter?
To avoid to much chemistry being concentrated in one area of the film.
What is the function of the developer?
Converting silver halide crystals to black metallic silver.
What is the function of the fixer?
Takes the emulsion and hardens it. It clears and hardens the film. It
cleans off the unexposed/undeveloped halide crystals off the film. They are dissolved off. When we do silver recovery to get it back and keep it out of streams of water we pass the fixer through a silver recovery device.
What would the image look like if the developer was too:
Cold?
Underexposed/Underreactive
What would the image look like if the developer was too:
Concentrated?
Overexposed (Fog)
What would the image look like if the developer was too:
Diluted?
Underexposed/underreactive
What would the image look like if the developer was too:
Oxidized?
Underexposed/underreactive
