Download Radiology PP 1 Ch 234

Radiology
Chapter’s 2, 3. & 4
By Garland Fisher
Electromagnetic spectrum
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Unique abilities
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Some rays visible
some are not
Penetrates matter
Produces latent image
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Produces fluorescence
 Light bulb
Produces ionization of
matter
 Change matter
Matter
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Anything that occupies
space and has mass
Matter can be altered
by energy
Fundamental unit of
matter is the Atom
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Desk
Chair
Computer
Tissue
Muscle
Teeth
Bone
Your Patient
Atom
Electrons
An atom is the smallest
unit of an element, it
consist of a positively
charged protons
found in the nucleus.
Negatively charge
electrons that orbit
around the nucleus.
Neutron
Proton
Electron
Nucleus
(Dense core that occupies very little space)
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Protons
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Subatomic particles and
positively charged
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Neutrons
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Subatomic particles and
has no charge
Nuclear Composition
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Equal number of protons
and electrons form a
stable atom.
The number of protons
and neutrons equals the
atomic weight.
Force will knock an
electron out of their orbit.
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X-radiation
Electromagnetic energy
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Is this Atom stable or
unstable?
Ionization
(production of ions)
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Converting atoms into ions.
To produce ions a force or a collision
such as x-radiation or electromagnetic
energy must eject an electron out from
its orbit. Thus making the atom unstable.
Spontaneous release excess energy in
the form of wave or particles.
ION
Electrostatic Force
Binding energy holds electrons in their orbits
(Example: sun and the planets)
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There are seven
shells an atom can
have they are k, l, m,
n, o, p, and q.
K-shell has the
highest energy and
the strongest binding
energy
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Nucleus
k
l
m
n
o
p
q
Atoms into ions
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Positive ions are
ionized atoms.
An ionized atom has
been interrupted by
some force:
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X-radiation
Electromagnetic energy
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Negative ions are electrons
out of orbit or unstable
structures.
This ejected ion will speed
off to interact with other
atoms.
When they interact or
collide it sets off a chain
reaction and in turn will
eject other electrons until
the energy dissipates.
Elements
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Elements
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Substances made up of only one type of Atom
Molecule
Molecule
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Two or more Atoms
make up a molecule
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Two Hydrogen and one
Oxygen = Water
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Bonded together by
electrons on the outer
most shells
Ionizing Radiation
(all radiation cause biological changes)
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Particulate
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Responsible for
radioactivity
Radioactivity is when
atoms spontaneously
disintegrate or decay.
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Power plant
Atomic bomb
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Electromagnetic
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Series of wave like
energies with no mass
some high energy some
low energy
Visible and invisible
Man made or natural
occurring
Electromagnetic Energy
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Made up of both wave and particle that
travel in a straight line
X-ray = bundle of energy, is termed, x-ray
photon which has no mass no charge and
travels at the speed of light (186,000 MPS)
X-ray photon is what interacts with matter
(your patient)
Examples of electromagnetic radiation
and there wave like patterns
Less
energy
More
energy
Electromagnetic Energy
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Wavelength
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Distance between the
crest of the wave to the
next wave
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Frequency
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Refers to the number of
wavelength that pass a
given point in a certain
amount of time. We can
adjust the frequency by
kilovoltage
Voltage
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Measurement of electrical force that cause
electrons to move from a negative pole to a
positive one (Strength)
Dental x-ray units require a high level of
electrical potential
Kilo-Voltage Peak
(KVp)
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Kilovoltage controls the
level of penetration
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Shorter wavelength =
more penetrating
High frequency =
more penetrating
Longer wavelength =
less penetrating
Low frequency the =
penetrating
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Kilovoltage
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Kilo = 1000
Volatage = volts 110 or 220
Higher voltage means
greater energies
Dental radiographs require
65 to 100 kilovolts
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Higher KVp should be used
when area is dense or thick
Adjust KVp on individual
diagnostic needs
Overall QUALITY of primary
beam
Amperage
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Measurement of electrons moving through a
conductor
Current is measured in amperes
Milliamperes (mA)
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Milliampere
 Milli = 1/1000
 Ampere = Electrical
current NOT voltage
mA settings
 7, 10, and 15
Thermionic emissions
 Higher the setting
increases temperature
resulting in some
electrons being ejected
out of their orbit.
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Ampere allows electrical
current to flow thru a
filament which results in a
cloud of electrons
Depending on mA setting
will depend on the
QUANTITY of x-rays
produced
Milliamperes-Seconds
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Exposure time
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Interval of time in which
photons are being
produced (.117 secs)
Longer time = more
photons
High mA = more photons
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Both mA and exposure
time both have a direct
influence on the
number of electrons
produced
If we produce to many
photons our dental film
will be dark or black
Radiographic Density
(Degree of darkness or blackness of an x-ray.)
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Density
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Amount of radiation
reaching the film
 KV or mA
Distance from the x-ray
tube to the patient
Patient thickness
(Density)
Developing conditions
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The more photons that
strike the film the more
dense (black) the
radiograph will appear
Tubehead
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Cathode
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Negative electrode
consist of tungsten
filament held in a cup
shaped holder made of
molybdenum
Negative = electrons,
therefore electrons are
created to produce
photons
*
Electrons
held in
place
Tubehead
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Anode
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Positive electrode consist
of a wafer thin tungsten
plate embedded in a
solid copper rod
Positive = collision =
photons
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Collision
produced
photons
(indicated in
red)
Transformers
Three types are used in production of x-rays
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Step down
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Step up
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decreases the voltage from the incoming 110 or
220 to three to five volts required
Increases the voltage to 65,000 to 100,000 volts
required
Autotransformer
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Compensator
Inside the Tubehead
This is What Happens
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Electricity excites the filament at 3-5 volts, creating thermionic
emissions, a release of electrons from the tungsten filament
when heated, this cloud of electrons stay in place until the
exposure button is pushed. The high voltage circuit is activated.
The electrons produce are accelerated across the x-ray tube to
the anode. The molybdenum cup helps to direct the electrons to
the tungsten target. When the electrons strike the tungsten target
their energy of motion or kinetic energy is converted to x-ray
energy and heat. More heat is created that x-rays and is
dissipated through the copper stem and absorbed by the
insulating oil. X-rays are produce in all direction only a few will
escape through the unleaded portion of the tube. Those x-rays
will be directed to the aluminum filter, which will remove the long
waves. The collimator will focus the remaining short waves and
travel down the lead lined PID and exit the tubehead
Production of radiation
(not all produce the same in the tube head)
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General radiation
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AKA braking radiation
An electron passes near the
nucleus and is deflected by
the positively charge
nucleus
Once deflected this kinetic
energy is converted into
photons
Add photo
Bremsstrahlung German
(braking radiation)
Production of radiation
(not all produce the same in the tube head)
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Characteristic radiation
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Electron that has been
deflected continues to
travel ejecting other
electrons out of orbit until
they loose their kinetic
energy
 Energy in motion
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