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1895- Roentgen’s discoveries X-ray or
Roentgen rays.
1896-Thomas Edison developed the first
fluoroscope
1896- first reported case of biological damage
1921 Potter-Bucky grid was introduced
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1942 first AEC was demonstrated
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1942 first automatic processor developed
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1986-1974 calcium tungstate screen
cassettes
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1970 Intensifying screens
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1979 First digital
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1982 PACS Picture Archiving &
Communications Systems ( storage & access
of digital images)
1982 Teleradiolgy
1980s CR Computed Radiography (cassette
converting images to electronic signal and
stored in a computer (filmless)
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1996 DR direct digital image is directly
captured by electronic elements with no
intermediate step ( cassettesless)
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¾ of all radiation we receive comes from
nature rather than technology
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Minerals in ground ( Terrestrial)
Cosmic
Internal
Radon
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Medical x-rays
Nuclear medicine
Consumer products
Fallout
Occupational
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As Low As Reasonably Achievable
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X-ray profession is a safe profession
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Discovery of x-rayNovember 8, 1895 by
Wilhelm Conrad
Roentgen in Germany
Roentgen’s wife's hand
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Crooke’s Tube
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Jackson Focus Tube
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Coolidge Hot Cathode
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Consists of the following:
◦ Highly evacuated glass tube
◦ Two sealed electrodes, Cathode and Anode
•Cathode- negative electrode, source
of electrons
•Anode - positive electrode, source
of radiation (x-rays)
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Contains a spiral, incandescent filament of
tungsten wire
Filament is heated by an electrical current of
low amperage from a transformer
Temperature of the filament, controlled by
the amount of current passing through it,
controls the number of electrons emitted
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Filament
◦ Source of electrons
 Filament current
 Thermionic emission
◦ Coiled tungsten wire
 Large and small
◦ Focusing cup
 Space charge effect
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Another reason for the high melting point of
tungsten is that the filament gets so hot it
actually glows. This glowing is called
incandescence. And the process is known as
thermionic emission.
When the filaments gets that hot it the
electrons are “boiled off” or freed from the
atoms.
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Higher the temperature of the filament, the more
electrons emitted
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Direct relationship
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Stream of electrons from cathode to anode is
known as the tube current
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Current is measured in milliamperes (mA)
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Stream of electrons are taken from cathode to
anode by a transformer (kVp)
◦ The speed with which the electrons cross the gap
between the cathode and the anode.
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Two types
◦ Stationary- could be melted from the intense
bombardment of electrons.
◦ Rotating- composed of metal with a good heat
conducting characteristics (molybdenum)
 Disc shaped anode is coated with an alloy made of
tungsten and rhenium
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Rotating anode
◦ Requires a stator and
rotor to rotate
◦ Tungsten metal
 High melting point
 Efficient x-ray
production
◦ Target
 Decelerates and stops
electrons
 Energy converted to
heat and x-rays
 Bremsstrahlung and
characteristic
interactions
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Voltage kicks in, takes electrons across the
tube
Thermionic Emission is a boiling off effect,
electrons move by heat raising the
temperature and the electrons boil off the
filament
Voltage is then responsible for taking the
electrons across the tube to the anode (kVp)
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Anode is made of tungsten and rhenium
because they have high melting points
Anode needs to slow down or stop the
electrons
Once electrons reach the anode they become
photons
Each photon accounts for one x-ray
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Who invented x-rays?
What year were x-rays invented?
What was the name of the first tube used
when x-rays were invented?
What was the problem with the first x-ray
tube?
What was the problem with the second x-ray
tube?
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X-ray production is the striking of matter by
high speed electrons.
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X-rays are generated in x-ray tube
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form of electromagnetic radiation
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Form of invisible radiant energy
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Have short wavelengths; gives x-rays ability
to penetrate materials that would normally
reflect or absorb light
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Two behaviors: Waves and Particles
Have shorter wavelengths than regular light
Consist of small bundles of energy called
photons
Wavelength vs. kVp
as kVp is increased, the wavelength of x-rays
decreases; indirect relationship
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A form of
electromagnetic
radiation
Behave both like waves
and like particles
Move in waves that
have wavelength and
frequency
Wavelength and
frequency are inversely
related
X-rays also behave like
particles and move as
photons
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Can penetrate materials that normally absorb
or reflect light due to short wavelengths
Cause certain objects to fluoresce- ability to
emit natural light.
Ability to penetrate solid and opaque
materials to produce an image
X-rays are invisible
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Can produce biological changes that can
stimulate or retard growth
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X-rays travel in straight lines
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Travel at the speed of light ( 186,000 miles
per second)
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Ionize gases by removing electrons from
atoms to form ions ( negatively charged
atoms)
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All x-ray tubes are a vacuums, free of air, air
impedes the flow of electrons
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X-rays are produced when energy is changed
from one ion to another
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Cathode is negatively charged source of
electrons
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Anode positively charged source of electrons
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Anode spins 3400 & 10,000 revolutions per
minute
Spinning the anode, prevents the same spot
on the anode from being hit by the stream of
electrons
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Exposure switch- two functions: rotor and
exposure
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Rotor- activates the anode to begin spinning
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Rotor also activates the electrons on the
cathode to begin to group and form on the
tungsten filament
Exposure switch- releases the electrons to be
propelled from the cathode to the target of
the anode and x-rays are produced
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mAs (milliampere quantity) controls the
amount of radiation that will be produced.
mAs supplies the current to the cathode
kVp (kilovoltage peak)(quality) is the voltage,
penetrating ability, power, strength of the
electrons traveling across the cathode to the
anode.
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The production of x-rays requires a rapidly
moving stream of electrons that are suddenly
decelerated or stopped.
◦ The negative electrode (cathode) is heated, and
electrons are emitted (thermionic emission).
◦ The electrons are attracted to the anode, move
rapidly towards the positive electrode, and are
stopped or decelerated.