Download Radiology Chapters 2,3,4

Radiology
Chapter’s 2, 3. & 4
Electromagnetic spectrum

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)

Protons
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Subatomic particles and
positively charged

Neutrons

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

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

Wavelength
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Distance between the
crest of the wave to the
next wave

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

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
*
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
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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Important Terms
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kVp = Kilovoltage peak=quality of beam
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kVp =
density = low contrast = lots of
shades of gray
Low kVp = low density = high contrast = lighter
film = black & white film
Contrast – varying shades of gray
Density – overall blackness or darkness of
film
Important Terms
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mA=Milliamperage=quantity of x-rays
produced=density
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To many mA’s=darker film=higher density
To little mA’s=light film=lower density
# of electrons from cathode to anode
# of x-ray photons in beam
mA regulates temperature of cathode
Important Terms
Exposure time – refers to interval of time x-rays
are produced-measured in impulses
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Longer time=longer time x-rays emitted=darker
film=greater film density
Less time=less time x-rays emitted=lighter films=
less film density
Subject Thickness effects quality and quantity
of penetrating power
Important Terms
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Kilovoltage peak rule – RHS – when kVp is
increased by 15 – exposure time should be
decreased by ½
When kVp is decreased by 15 – exposure
time should be doubled
Milliampere-seconds (mAs) = combination of
milliamperes and exposure time
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Milliampers X exposure time (seconds) =
milliampere-seconds (increase mAs-decrease
time)
Important Terms
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Attenuation aka Dose
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Primary Radiation aka Primary Beam
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When matter absorbs radiation (only during
secondary)
Penetrating beam – Roentgen Units = R
Secondary Radiation
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Created when Primary beam hits matter (soft
tissues, head , skull, teeth) less penetrating power
Radiation pt receives – RAD = radiation absorbed
Important Terms
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Scatter Radiation
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A type of secondary radiation
Has been deflected off of path
Travels to all parts of the body & operatory
REM = Roentgen equivalent to man
MPD = maximum permissible dose
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Dental radiographer = 5.0 REM per year
Non health care worker = .1 REM per year
.08 RAD’s in FMX
Radiation Biology
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Radiation Biology-the study of effects of
ionizing radiation on living tissue
Absorption
Ionization page 39 – all x-rays harmful to
living tissue
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When x-rays strike patient tissues ionization
results
Free Radical Formation-causes cell damage
Sequence of Radiation Injury
page 41
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Latent Period=the time that elapses between
exposure to ionizing radiation and the
appearance of visible clinical signs.
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Example: Sitting in the sun – hours later skin
redness appears
Sequence of Radiation Injury
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Period of injury
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After the latent period
Cell injury can result as:
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cell death
changes in cell function – ex: endometriosis
breaking or clumping of Chromosomes – ex: (cell)
reproduction problems
many more cell specific
Cell injury is the desired result in cancer tx
Sequence of Radiation Injury
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Recovery period
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Not all cell radiation damage is permanent
Damage caused by low-level radiation is repaired
within cells of body. Ex: skin was burned – it has
repaired itself
Sequence of Radiation Injury
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Cumulative effects – overtime
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Radiation damage accumulates in tissue of entire
body
Can lead to:
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Poor health
Cancer – Thyroid/Skin
Cataract formation
Birth defects
Dental x-rays do not cause cancer – falls under
MPD
Sequence of Radiation injury
cont.
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Recovery period=Not all cellular radiation
injuries are permanent. With each radiation
exposure, cellular damage is followed by
repair.
Cumulative effects=The effects of radiation
exposure are additive, and unrepaired
damage accumulates in the tissues,
cumulative effects of repeated radiation
exposure can lead to health problems.
Determining Factors for
Radiation Injury
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Total dose – RAD – measurement of
attentuation – absorbable dose
Dose rate – rate @ which exposure to
radiation occurs & absorption takes place
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Cells need time to recover
Amount of tissue irradiated – area exposed
Cell sensitivity
Age
Short-Term and Long-Term
Effects
Short-term page 42
 Short-term effects are
associated with large
mounts of radiation
absorbed in a short
time. Includes nausea,
vomiting, diarrhea, hair
loss and hemorrhage.
Long-term page 42
 Effects that appear after
years, decades or
generations. Long-term
effects are associated
with small amounts of
radiation absorbed
repeatedly over a long
period.
Somatic and Genetic Effects
Somatic effects
 Somatic cells are all the
cells except reproductive
cells. Major somatic
effects of radiation
exposure include the
induction of cancer,
leukemia and cataracts.
These are not transmitted
to future generations.
Genetic effects
 Genetic effects are not
seen in the person
irradiated but are passed
on to future generations.
The radiation-induced
mutations affect the
health of the off-spring.
Genetic damage cannot
be repaired.
Radiation Measurements MPD,
Maximum Permissible dose
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The dental radiographer must know radiation
measurements to discuss exposure and dose
concepts with the dental patient.
Traditional or standard system
R-roentgen=measurement of radiation
REM (Me)=5.0 year or .01 weekly
Pregnant operator=0.1 per year
RAD (pt.)=0.1 per year
Risk Estimates
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Radiosensitive parts
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Lymphoid tissue
Blood forming tissues
Reproductive cells
Formative cells
Embryo cells
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Radioresistant parts
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Salivary glands
Kidney
Liver
Cells of mature bones
Muscle
Nerves
Critical Organs
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Thyroid Gland
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Bone Marrow
Skin
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Use Thyroid collar
Very sensitive to radiation
Eyes
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Cataract
Patient Exposure and Dose pg.
46
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Film- Using F-speed film instead of D
reduces absorbed dose by 60%. Using
F-speed instead of E reduces absorbed dose
by an additional 20%
Collimation-Radiation exposure can be
limited by using rectangular collimation,
reduces absorbed dose by 60%-70% rather
the round collimation (PID).
Patient Exposure and Dose
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Technique-Radiation exposure can be limited
by using a longer source-to-film distance.
XCP for example
Exposure factors-Radiation exposure can be
limited by using a higher Kilovoltage peak,
the use of higher kilovoltage peak reduces
skin dose.
Surface exposure-intensity of radiation @ pt
skin surface
REDUCING EXPOSURE RISKS
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Dental radiation risks – estimated 3
to1,000,000
30 PA’s to equal one chest x-ray’s worth of
radiation
Film speed
Collimation – PID use of Rectangular best –
most common is round – pointed not used
Technique – use film holding devices
Exposure – higher kVp less time
Risk versus Benefit
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X-radiation is harmful to living tissues
Benefit of disease detection outweighs risk of
biological exposure
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Properly prescribed & exposed – only when
needed
ALARA Principle – as low as reasonably
achievable – minimize risk to pt and operator
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FMX – full mouth survey – taken no more than
once every 3-5 yrs – 14 PA’s & 4 BW’s