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115 terms

Veterinary Imaging test 2

STUDY
PLAY
If you manually process a film, what is the minimum time a film must stay in the fix before it can be briefly viewed and exposed to room light?
1 minute.
What is the RULE OF THUMB for manual processing?
Fix the film twice the developing time
What is the inverse square law for SID?
double the distance from the tube to film means 1/4 radiation reaches film ( decrease film density )
What are the 3 functions of a radiographic cassette?
1. To provide close, tight contact between the film and the intensifying screen.
2. Provide a light-tight container for the film
3. Protect the screen and film from physical damage
What are the two types of radiographic cassettes?
Aluminum and Plastic
Why is the radiographic cassette lined with metallic back?
to prevent backscatter
Wha size is the rectangle of lead on the front that allows use of the photoimprinter?
7 X 3cm
What are the four functions of intensifying screens?
1. Line front and back of cassette
2. Made of plastic sheet coated with PHOSPHOR material suspended in binding agen
3. Emits light when exposed to x-rays
4. reduces the amont of scatter radiation necessary to expose film (*****)
The screen speed is demermined by the size of the _________ _________.
phosphor crystal
What are the four characteristics for high speed screens?
1. Larger crystals
2. less radiation needed
3. poorer resolution
4. more graininess
What are four characteristics for slow speed screens?
1. Smaller crystals
2. More radiation needed
3. better resoultion
4. less graininess
Do high speed screens have larger or smaller crystals?
larger crystals
Do slow speed screens have larger or smaller crystals?
Smaller.

(S for slow and smaller)
What are the 3 different types of intensifying screens?
1. Rare Earth Screens
2. Hi-Plus Screens
3. Ultra Detail Screens
What are 4 characteristics of a Rare Earth Screen?
1. Higher speed screen
2. Larger crystal ( rare earth elements)
3. Higher cost
4. an attempt to combine high speed with good resolution
What is Quantum Mottle?
a mottling that can be seen on the film when using rare earth screens and very low exposures.

this is due to extreme sensitivity of rare earth phosphors to x-ray radiation.
What are 4 characteristics of Hi-Plus screens?
1. considered a medium speed screen
2. Medium sized crystal ( calcium tungstate)
3. average resolution
4. used for general x-rays
What are 4 characteristics for Ultra Detail Screens?
1. A slow speed screen
2. Smaller crystals
3. excellent resolution
4. useful for orthopedics
What are four important details of screen care?
1. clean monthly
2. use commerical screen cleaner or mild soap/water
3. record when cleaned
4. check adhesion to cassette when cleaned
What are 2 facts to remember about the construction of film?
1. Silver halide crystals are suspended in gelatin on both sides of plastic acetate base
2. Covered with a protective coating
What 3 things happen in the latent image production?
1. x-rayss hit screen phosphor crystals
2. screen phosphor crystals emit visible lgiht
3. Visible light from screen causes a change in silver halide on the film producing an invisible "latent image"
When is the latent image made visible?
when film is processed
What are the two types of film ?
1. Screen Film
2. Non-screen film
Is screen film or non-screen film more sensitive to visible light than x-rays?
Screen Film
Is screen film or non-screen film more sensitive to xray radiation than visible light?
non-screen film
Regular screen film is more sensitive to _____ light
blue light
Rare earth film is more sensitive to ______ light
green light
What film type is common for dental and orthopedic film?
non-screen film
Which film types needs more AND less radiation to expose film?
screen film= less radiation
non-screen film= more radiation
What is the Fast Speed Film also known as?
Ultraspeed
What is the Medium Speed Film also known as?
Par film/ Standard film
What is the Slow Speed Film also known as?
High detail film
What are three characteristics of Fast speed film?
1. Larger silver halide crystals
2. need less exposure
3. less detail
What film speed is most common?
Medium Speed Film
What are three characteristics of Medium Speed Film?
1. Medium-sized cyrstals
2. Medium exposure
3. Medium detail
What are 4 characteristics of Slow Speed Film?
1. Small cyrstals
2. Increased exposure
3. Increased detail
4. Greater latitude in exposure factors
What are 4 important things are important to remember for film care?
1. Store film vertically
2. Keep in cool area/ low humidity
3. Avoid formalin/ hydrogen peroxide/ ammonia vapors
4. Check film experation date
What is a grid?
Alternating thin strips of lead with spacers in between them.
What does a grid do?
absorbs any x-rays that are not parallel to the primary beam
What is a grid ratio?
The height of the lead strip divided by the distance between them.
Finish this sentence:
The greater the grid ratio _______________
the more efficient the grid
What are the 3 grid types?
1. Parallel Grid
2. Focused Grid
3. Crisscross Grid
What is a Parallel Grid?
When all lead strips are perpendicular to the table
What is a focused grid?
when the lead strips are parallel with the natural divergence of the primary beam
Which type of grid is most common?
Focused grid
What is a crisscross grid?
2 parallel type grids superimposed on each other.
What is a grid cut-off?
Refers to the absorption of part of the primary beam due to improper use of the grid.
What is the grid cut-off caused by?
1. focused grid used upside down
2. focused grid used with primary beam not centered over grid
3. focused or parallel grid not perpendicular to x-ray tube
4. focuse grid used with incorrect SID
What is a grid factor?
a portion of the primary beam is absorbed by any grid
it is estimated that __% of poor quality radiographs can be traced to poor processing.
90%
What is film processing?
Refers to the process of turning the latent image into the visible image on the film.
In order, what are the five steps of film processing?
1. Develop
2. Rinse
3. Fix
4. Wash
5. Dry
What are the 4 darkroom essentials?
1. Must be kept clean
2. Keep organized and uncluttered
3. Must be light-proof
4. Must be well ventilated
What are the 5 darkroom rules?
1. Keep area clean
2. Keep developer and fixer tanks covered
3. Stay organized
4. Handle film by edges
5. Remove film slowly to avoid static
The safelight uses ___ watt _____ since xray film is most sensitive to blue/green light
15 watt

redlight
Developing is the process of what?
the process of reducing the exposed silver halide crystals to black metallic crystals
The developer consists of what 5 things?
1. reducing agents
2. ALKALINIZER
3. Restrainers
4. Preservatives
5. Water
The rinse bath is compused of usually water and does what?
1. removes developer
2. reduces carry-over of developer into fix

can also be acid
The fixer is also known as the _____ agent
clearing agent
What does the fixer remove?
unexposed silver halide crystals
The time in the fix is dependant on what 2 things?
1. time to remove the unexposed crystals
2. time to harden the film emulsion
What 4 things does the fixer consist of?
1. ACIDIFIER
2. Hardener
3. Preservative
4. Water
Washing removes what?
removes fixing agent
When manually processing, all soultions should be ideally at __ degrees.
68 degrees
When manually processing, the final wash time is usually for how many minutes?
20-30 minutes
What are 4 advantages to automatic processing?
1. reduces developing and drying time
2. reduces artifacts
3. more consistent processing
4. less expertise required
What are 2 disadvantages for automatic processing?
1. higher initial cost
2. periodic maintenance
How do you know when the developer needs to be changed?
1. when it is green or brown
2. when films have less contrast and appear underexposed
The fixer needs to be replenished when clearing time is what?
more than 3 minutes
What are the three legal methods for film identification?
1. Lead letters placed on cassette at time of exposure
2. lead labelling tape on cassette at time of exposure
3. photoimprinter used in darkroom after exposure
Film identification must be __________ and ______ to be legal?
Permanent and ulalterable
If label is forgotten on film you can use what?
1. pencil
2. white ink or permanent magic marker
3. white tape
Identification on film should include what 5 things?
1. Name of hospital or practice
2. Date of film taken
3. Name or number of patient
4. Owners name
5. X-ray view or orientation
Legally, you must keep x-rays for a minumum of __ years
7 years
Films are filed in envelopes with what following information?
1. Owners name
2. Pet's name
3. Radiographic views
4. Date of exposure
Radiographic quality is based on what 3 things?
1. Density ( overall blackness )
2. Contrast ( Adjecent density )
3. Definition
A diagnostic radiograph will have what 4 characteristics?
1. Sufficient density
2. Sufficient definition
3. Sufficient contrast
4. Sufficient penetration
What does it mean to have sufficient density on a diagnostic radiograph?
1. adequate blackness on the radiograph
2. Reveals all structural details of the object
3. Too much density will hide detail
What does it mean to have sufficient definition on a diagnostic radiograph?
able to differentiate body parts from each other
What does it mean to have sufficient contrast on a diagnostic radiograph?
provides variations in tissue opacity
What does it mean to have sufficient penetration on a diagnostic radiograph?
provides internal detail, not just tissue silhouettes
What are the 3 factors affecting x-ray penetration?
Wavelength, Subject composition, and Tissue thickness
Short wavelengh=
increased penetration
Increased thickness=
decreased penetration
What are the 4 factors that can affect the radiographic image?
1. MA
2. KVP
3. Time
4. Distance (SID)
What does MA control?
Quantity of x-rays
Density of film
What does KVP control?
quality of x-rays
penetrating power of x-rays
contrast on film
What does TIME control?
determines the length of exposure
quantity of x-rays
density of film
What is the inverse square law?
Increase distance= decrease amount of radiation per square inch reaching film = causes decrease in density of film
When looking at film density what does many blacks equal?
high density
When looking at film density what does many whites equal?
low density
Radiolucent =
black on film which means the most radiation hitting the film

ie gas
Radiopaque =
white on film which means the least radiation hitting the film.

ie bones
The greater the tissue density =
lesser the film density
What are the 5 patient densities of concern in radiology? In order.
1. Gas
2. Fat
3. Water
4. Bone
5. Metal

From least dense to most dense.
What is high contrast and what is it also called?
It is abrupt changes of density tones from black to white

also called SHORT SCALE
What is low contrast and what is it also called?
Gradual changes of density tones from black to white

also called LONG SCALE
High contrast = short scale = low ____ and high ____.
Low KVP and high MAS
Low contrast = long scale = high ___ and low ____
High KVP and Low MAS
What is a wide latitude film?
film that needs large changes in exposure to change visible density
What is short latitude film?
film that shows density changes in response to minor changes in exposure.
Definition or image sharpness is affected by what three things?
1. motion
2. Geometric unsharpness
3. Material Unsharpness
How does magnification distort a radiograph?
causes object to appear larger than it really is and the object is not as close to film as possible
How does elongation distort a radiograph?
when the x-ray tube is not perpendicular to object,
How does foreshortening distort a radiograph?
when object is not parallel to the film
A radiographic film is exposed by what two things?
light and radiation
What are the two main questions that should be asked when critiquing the quality of a radiograph?
1. Is the film too light or too dark?
2. Is the density suitable?
What are the questions that could be asked before submitting the radiograph to the veterinarian?
1. Film too light or too dark?
2. Is the density suitable?
3. Was the entire area of interest represented?
4. Did I collimate correctly?
5. Do I have a R/L directional label?
6. Is the film labeled?
The standard change in KVP to increase or decrease penetration is _____%
10-15%
To improve a radiograph by altering the density, the MAS is increased or decreased by _______%
30-50%
What would a radiograph look like if it was inadequately penetrated?
the anatomical parts are indistinct or imperceptible
If the film is overpenetrated it will be what?
too dark
What is responsible when a radiograph has an overall gray appearance?
High KVP
Insufficient density is usually indicated if the film is what?
too light and the anatomical silhouettes of interest are visible.

The image is visible but not dark enough to see well
If the film is too light or too dark is it due to KVP or MAS?
KVP