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73 Cards in this Set

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  • Back
Radiograph
is produced from X-rays passing through a patient's body and interacting with the emultion (surface) of a radiographic film.
Exposure Factors
1.mA, time, kVP, SID
2.heel effect, tube alignment to film & body part, OID, tissue thickness/pathology, screen selection, collimation and beam filters, fog & film processing
Density
def. - overall blackness of the total image.
-controlled by mAS
mAs
1. main controlloing factor of density
2. secondary controlling factor of contrast
3. controls amount electrons at the cathode (quality of radiation)
4. double mA,time,mAs=double density
5. hald mA,time,mAs=half density
6. mAs is the product of mA & time.
7. use the triangle for mAs
Reciprocity Law
def. - this law means that any combination of mA X T factors taht are equivalent mAs should produce the same amount of density.
Smaller Focal Spot
Advantages:
1. results in greater recorded detail to image.
Disadvantage:
1. longer (slower) exposure time may result in patient motion.
2. focal spot cannot tolerate heat generated by a long exposure.
Larger Focal Spot
Advantages:
1. shorter (faster) exposure time minimizes risk of patient motion.
2. focal spot can tolerate increased heat generated by longer exposure times.
kVp
1. secondary controlling factor of density
2. quality of radiation
3. controls penetration
4. main controlling factor of contrast
5. 1 kV=1000 V
6. to double density increse kV 15%
Inverse Square Law

I =new intensity
I =old intensity
D =old density squared
D =new density squared
def. - the intensity of radiation is inversely proportional to the square of the distance.
**use w/problems w/mR or R & distance.
Anode Heel Effect
1. intensity of the beam is greater at the cathode end of the beam.
2. greatest w/large cassettes & when part is thick on one end & thin on other end
3. used for: femum, thoracic spine
Film Fog - Density
density may affect by film fog w/c is unwanted density that makes it difficult to visualize structures on the radiograph.
causes:
1. aged/old film
2. light (result in total blackening of film emulsion)
3. scattered radiation exposure, or improper film development.
4. to prevent or reduce film fog - darkroom must be lightproof.
Artifacts
are foreign or unwanted marks that show up on radiograph due:
1. improper film handling
2. improper processing
3. faulty equipment
Half-moon/Crescent marks
pressure may times from fingernails
Static Electricity
spidery black lines on processed film
Improper washing
greasy film
Light spots
dirt or dust on the intensifying screens
Emulsion peeling of the film
"Reticulation: caused from drastic change in temperature from the developer to the fixer
Film & Screens
a. Base-polyester
b. Active crystals: Silver bromide(in gelatin)
c. More sensitive after exposure to x-ray or light
d. Must be stored in a cool, dry place
e. Latent image-created when film is exposed to light and/or x-ray
f. manifest image: created when film is exposed to x-ray or light and develope(visible image)
g. back of most cassettes lined with thin layer of lead: to absord backscatter
h. for best results match the film base tint with the color of light that comes off the screen
Long-scale contrast
several degrees of gray to black tones will be produced in the image w/higher kVp above 70 kVP
Short-scale contrast
the range of gay tones is more abrupt from white to black. Fewer gray tones will be seen in the image is produced at lower kVp ranges below 70 kVp
FSS, SID, OFD
Focal-Spot Size
Source-to-image-distance
Object-film distance
SID
-has no effect on the penetrating power of kVP

- will not affect contrast as long as the kVp remains unchanged.

- greater SID will reduce geometric blur(pnumbra) & improved detail.
Intensifying Screens
-have phosphors that intensify the action of radiation.

-2 important elements of screens
1. size of the crystal
2. thickness of layer of phosphor.

categories of screens
1.detail - slow
2.general purpose-medium
3.fast-high speed
Grids
def. is designed to be used where density of the image is affected by the amount of scattered radiation reaching the film. Placed under the table between the patient & film.
Grid Ratio
is the ratio of the height of the lead strips to the distance between the led strips.
Filtration
is the process of filtering the beam of radiation through some tye of material that will remove lower-energy radiation from the beam & prevent it from reaching the patient.
Artifacts
are foreign or unwanted marks that show up on radiograph due:
1. improper film handling
2. improper processing
3. faulty equipment
Half-moon/Crescent marks
pressure may times from fingernails
Static Electricity
spidery black lines on processed film
Improper washing
greasy film
Light spots
dirt or dust on the intensifying screens
Emulsion peeling of the film
"Reticulation: caused from drastic change in temperature from the developer to the fixer
Film & Screens
a. Base-polyester
b. Active crystals: Silver bromide(in gelatin)
c. More sensitive after exposure to x-ray or light
d. Must be stored in a cool, dry place
e. Latent image-created when film is exposed to light and/or x-ray
f. manifest image: created when film is exposed to x-ray or light and develope(visible image)
g. back of most cassettes lined with thin layer of lead: to absord backscatter
h. for best results match the film base tint with the color of light that comes off the screen
Long-scale contrast
several degrees of gray to black tones will be produced in the image w/higher kVp above 70 kVP
Short-scale contrast
the range of gay tones is more abrupt from white to black. Fewer gray tones will be seen in the image is produced at lower kVp ranges below 70 kVp
FSS, SID, OFD
Focal-Spot Size
Source-to-image-distance
Object-film distance
SID
-has no effect on the penetrating power of kVP

- will not affect contrast as long as the kVp remains unchanged.

- greater SID will reduce geometric blur(pnumbra) & improved detail.
Intensifying Screens
-have phosphors that intensify the action of radiation.

-2 important elements of screens
1. size of the crystal
2. thickness of layer of phosphor.

categories of screens
1.detail - slow
2.general purpose-medium
3.fast-high speed
Grids
a. Bucky:
1. moving grid
2. if lines appear on
radiograph: bucky is not
turn on
b. Increase grid ratio - increas in technical factors
c. higher grid ratio-more critical centering
d. Focused grid has a specific SID range that must be used or get grid cutoff
e. Purpose of a grid: to eliminate some scatter from reaching the film.
Grid Ratio
is the ratio of the height of the lead strips to the distance between the led strips.
Filtration
is the process of filtering the beam of radiation through some tye of material that will remove lower-energy radiation from the beam & prevent it from reaching the patient.
Location of Darkroom
-ventilation constant flow of fresh air w/a temperature 60-70F degrees.
-humidity 40-60%
-walls adjacent to radiographic rooms s/b shielded w/1.6mm (1/16 inch) lead all the way to the ceiling to protect unexposed film from radiation exposure.
Radiographic Film
consists of two parts:base & emulsion. Base made of polyester and emulsion contains the crystals that will hold the latent image formation. (Silver halide crystals)
Spectral Absorption
commonly called spectral matching refers to the use of film whose sensitivelty is correctly matched to the light spectrum emitted from teh intensifying screen.
Calcium-tungstate intensifying screen
emit blue & blue violet light & should be matched to silver halide emulsion film or blue-sensitive film.
Rare-earth intensifying screens
should be matched to screen film taht is sensitive to gree light.
Radiographic film is sensitive?
X-rays, heat, light, chemical fumes, moisture, pressure & any kind of rough handling ex. bending, scratching, crimping etc. fue, chemicals & gas substance. Films should be store upright.
Film Fog
undesirable increase in the density of the emulsion either before or after radiation exposure. decreases quality of radiographic image.
Intensifying Screens
-look like thin sheets of plastic
-different size according to corresponding to film sizes.
-screen is mounted inside the cassettes.
-screen has 4 layers: protective coating, phosphor, reflective layer and base.
Protective Coating
outermost layer of the screen & closest to the film
Phosphor
or active layer is responsible for emitting light when struck by Xray. or converting the energy of xray beam into visible light. ex. rare-earth or calcium tungstate
-high atomic number
-high conversion efficiency
-spectral mathcing
-phosphorescence
Rare-earth screens
high speed, require less xray exposure to the patient
Screen Speed
-screen's ability to produce density with a given exposure to X-rays.

-the higher the speed the more density will be produced at a given exposure.
Resolution
"rule of thumb" conditions that increase the intensification factor reduce resolution. This means that high speed screens with their large size phosphor crystals wil have a lower resolution that fine detail screens
Poor screen-film contact
1. air trapped btween screen & film.
2. foreight matter on the screen surface
3. improperly mounted screen
Basic Steps of Film Processing
1. Developer
2. fixer
3. washer
4. dryer
Automatic Processing
involves higher solution temperatures & shorter processing times.
Developer
changes silver bromide into black metallic silver
Fixer
1. hardens emulsion
2. clears unexposed silver bromide crystals
Preservative
common ingredient to developer and fixer
Roller-transport system
controls the processing time
Safelight
1. fogging depends on the distance from the safelight & length of time the film is exposed to the safelight
2. 3ft from workbench
3. 15 watt bulb
Manual processing
if developer temperature is up the technician should decrease the development time.
Replenishment
is used to restore both developer and fixer chemicals to their original strength
Microswitches
located at the entryto the feed tray detect the film size & start the automatic chemical-replenishment pump
Sharpness of detail
1. main contributing factors: focal spot size, OFD,(OID), FFD(SID)
2.the higher the scren speed the less the definition
Distortion
1. distortion=misrepresentation of shape
2. magnification=misreprsentation of size,#1 cause >large OID and SID also hs an effect
3. shape distortion cause: film, tube & part not parallel to each other
4. increased SID & decreased OID will give the least magnification and best detail
Scattered/Secondary Radiation
def. - radiation that has deviated in driection after passing through matter.
1.patient #1 cause
2.as you increase kVp you increase scatter
3.collimation decreases scattered radiation
Technique chart
1. based on body part measurement in centimeters measured with a caliper
2. technician must use before making exposures
Devices used to analyze films:
1.Densitometer: reads densities
2.Penetrometer:reads penetration(kV-quality of the beam)
3.Spinning top test:checks rectifiers
4. Milliameter-checks current
5. Sensitometry-checks processor
mAs-Distance Formula
(Rule of Thumb)
When the distance is exactly in half one-fourth(1/4) of the original mAs is used to maintain tghe proper radiographic density. If the SID is doubled then four (4) times the original mAs is necessary to maintain the proper radiographic density.
kVp & Density
(Cut the mAs in 1/2)
a 15% in kVp is equivalent to a 50% increase in density on the radiograph, therefore in order to maintain the same radiographic density, every 15% increase in kVp must be accompanied by a 50% reduction in mAs.
kVp & Density
(Double the mAs)
a 15% decrease in kVp is equivalent to a 50% reduction in the density on the radiograph therefore, in order to maintain the same radiographic density every 15% reduction in kVp must be accompanied by a 50%increase in mAs.