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What is the importance of spectral matching in selection of screen film combinations?
Rare earth screens; it must match
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Amber filter
Blue sensitive film
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Red filter
Green and blue
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Proper film storage
- Temp 20 degree Celsius 68F
- Humidity >60%
- Shelf life - cool dry place
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Other name for fixer
Hypo
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Principal of development
Convert latent image to manifest
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Why does film go through fixer tank?
Washes off the unaffected silver halide
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Brown film
Fixer retention
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Physical qualities required for to be used as a intensifying screen base?
Polyester plastic
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Typical radiograph intensifying screen
Base,reflective layer,phosphor,base,contact felt, low z front , low z back
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Radiographic film contributes to latent image?
Fewer than 1%
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Why are two screens placed in a radiographic cassette ?
Reduce patient dose
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Name 5 phosphors
Barium flurochloride, barium sulfate,zinc sulfide, calcium tungstate, lanthanum
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Quantum mottle
Radiographic noise produce by the random interaction of x ray with intensifying screen
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Four exposure technique factor; how does each affect OD
- Kvp - number of X-rays in image forms beam
- mA - number of X-rays produced radiation quantity
- Exposure time (s) minimize motion blur the can occur during patent motion.
- SID - determines the intensity of X-ray beam at IR
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Components of total X-ray beam filtration
Inherent,compensating, added filtration
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Why is it important to keep exposure time as short as possible
Dosage minimize patient motion blur
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Large focal spot
Sufficient mAs used to image thick or dense body parts, shorter exposure time. More X-rays at anode
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Small focal
Electron interaction over smaller area of anode; finer detail
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OD
- Black OD 3 or greater
- Clear is less than 0.2
- Light OD of 2
- Useful range 2?
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High OD
Over exposure too dark
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Change in OD req what technique
- Fix distance
- MAs used to control OD change in 30% mAs is used to produce a visible image
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Body habitus
Thicker body = more strength
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Advantage of large focal spot over small
Large - more X-rays
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Contrast
Difference in OD between adjacent anatomical structures or the variations in OD on a radiograph
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High contrast
Bones spinal column
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Low contrast
Psoas muscle, kidney
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Radiographic film cross section
Super coat, emulsion, adhesive, base, adhesive, emulsion, supercoat
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90 second processor
Developer fixer washing drying
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Process whereby latent image is created in one crystal of the film emulsion
The exposed crystal , electron collected at sensitivity center. These elections concert silver jobs to atomic silver
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Gloves goggles
Toxic skin burns eye irritations
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Proper dark room procedure
Color watt distance from film
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Reg screen film
Double emulsion
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Mammography
Single screen single side emulsion
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Photon
Electromagnetic radiation that has neither mass nor electric charge but interacts with matter as though it's a particle
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Alpha particle
Particulate from of ionizing radiation that consists of two photon an two neutron.
Helium emitted from nucleus of radioactive atom
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Fundamental particles within an atom
Electron proton neutron
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Property of an atom does biding energy describe
Electron closer to nucleus Stronger binding
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Can atoms be ionized by Changing number of positive charges ?
No, bound strongly together and that action would change type of atom
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How are ion pairs formed?
Opposite charged particle come together
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Why doesn't an electron spontaneously fly away from nucleus atom ?
Tightly bonded strength = certain amount of energy to release
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X-rays
- Electron cloud
- Produced outside nucleus of excited atoms
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Gamma ray
Produced inside the nucleus of radioactive atoms
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Alpha particles , beta particles
- Nucleus
- Particulate radiation
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Energy
Ability to do work
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Derived quantity
Secondary quantities combination one or more of the three base quantities
Volume density velocity
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Ionizing radiation
Any electromagnetic that had sufficient energy to remove an electron from an atom
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Air kerma
- 1/1000 of a rad
- 100 ergs of energy absorbed per gram of tissue
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Average level of natural enviromental radiation
300mrad yr
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The Coolidge tube
First heated filament X-ray tube
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Fluorscopy
Real time x ray
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Acceleration
Rate of change over time
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Barium platinocyanide
Phosphor fluorescent material
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1895
Roentgen discovers X-rays
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Roentgen Noble prize
1901
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Coolidge hot cathode x eh tube
1913
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Weight different from mass
- Weight is determined by gravity
- Mass is constant
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For examples of electromagnetic radiation
X rays gamma rays visible light radio waves microwaves infrared radiation ultra violet radiation
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X-rays vs electromagnetic radiation
X-rays interact at electron level or nuclear level
Electromagnetic interact molecules cells
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Purpose of X-ray filtration
Lower patient radiation dose
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Formation of negative ion and positive ion
X-rays electron absorbs energy and is release from atom + - ion pair
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Spatial resolution
Ability to image small objects that have high subject contrast
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Spectral matching
Rare earth screens only in conjunction with film emulsion that have lift absorption match light emission of screen
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Phosphor
Active layer of the radiographic intensifying screen closest to radiographic film
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Luminescence
Emission of visible light
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Kvp
Measure of the maximum electrical potential
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mAs
Product of exposure time and x ray tube current. Measure total number of electron
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Beam penetrability
Ability of an X-ray beam to penetrate tissue
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Sid
Distance from X-ray tube to IR
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Inherent filtration
Filtration of useful X-ray beams provided by the permanently installed components of an film emulsion
X-ray tube housing assembly an glass must match light emission
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Solvent
Liquid in to which various solids and powers can be dissolved
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Sensitive center
Physical imperfections on the lattice of emulsion layer that occur during the filming manufacturing process.
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Latent image
Unobservable image stored in the silver halide
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Silver halide
Active ingredient of radiographic emulsions
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Spectral matching
Use of rare earth screens only in conjunction with film emulsions that have light absorption characteristics matched the light emissions of the screen
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Artifact
Unintended optical density on a radiograph or another film type of IR
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Radiation fog
Artifact caused by unintended exposure to radiation
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Shelf life
How long before it expires
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Orthochromatic
Referring to blue it green sensitive films
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Screen speed
Relative number used to identify the efficiency of conversion of X-rays in to usable light
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Archival quality
Image does not deteriorate with age but remains in original state
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90 sec processor
- Developing 22sec
- Fixer 22
- Washing 20
- Drying 26
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High contrast
Smaller crystals uniform grain size
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Low contrast
Larger crystals wider range sizes
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Direct exposure film
- Thicker emulsion an more crystals
- Not sensitive to light
- Increased dose
- Very detailed
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Screen construction
- Polyester plastic base - support layer
- Phosphor layer - active layer
- Reflective layer - increase screen efficiency
- Protective coating
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Isotropically
X-rays emit ^ equal intensity in all directions
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X-rays emitted through window or port
Useful or primary beam
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X-ray tube made of
Pyrex glass or metal enclosure to withstand high heat load and minimize X-ray absorption
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Cathode two parts
Filament focusing cup
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Outer shell electrons boiled off
Thermionic emission
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Anode +
Conducts electricity radiates heat contains target
Two types stationery and rotating
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Anode heat
- 99% kinetic energy to hear
- 1% converted to X-rays
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Anode heel affect
The smaller the anode angle the larger the heel affect
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