Basic Radiation Concepts
This unit will provide a basic
understanding of atomic
theory, energy, and x-ray
properties.
Branches of Science
Natural Science
Physical Sciences
Biological Sciences
Non-living matter
Living matter
Physics
Astronomy
Zoology
Botany
Matter & energy
Heavenly bodies
Animals
Plants
Chemistry
Geology
Virology
Matter & its changes
Earth
Viruses
Branches of Science
There are many other branches of scientific study
throughout the world, but these are the most important to
the radiologic technologists.
– Anatomy – study of the structure of organisms
– Physiology – study of organism functions
(especially organ systems)
– Biology – study of all forms of life
– Chemistry – study of atomic particles (matter)
& their interactions
– Physics – study of physical world & laws governing all physical
objects
– Radiology – study of radioactive particles & their properties
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Matter
• Anything that has mass, occupies space, and
has shape or form.
• Measured by its mass
– The quantity of matter in an object
Matter has mass whether it is a
gas, liquid, or a solid.
Mass vs. Weight
• Mass is:
• Weight is:
– Measured in Kilograms
– Represents the weight
of a standard piece of
platinum-iridium
– Equal to 1000cm3 of
water at 00 C
– Remains constant
regardless of
environment
– Force exerted on a
body by a gravitational
field
– Can vary according to
environment
– Sometimes used
interchangeably with
mass, but not the same
Matter
Structure of Matter
Mixture
Substance
Element
Compound
atom
molecule
• Mixture - the combination of two or
more substances.
• Substance – any material with a
definite, constant composition.
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Elements
• Simplest forms of substances that compose matter
• Cannot be broken down into simpler parts by
ordinary means
• Each element has only one unique type of atom in
it with a set number of protons
• There are 92 naturally-occurring elements & over
a dozen “man-made” elements
The Periodic Table
The Periodic Table
Number of protons in
nucleus
Mass of
components
of atom
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Atoms
• Matter is composed of basic “building blocks” called
atoms.
• Atom is the smallest particle
of an element that still possesses
the chemical properties of that
element
• The atom is the smallest form of
structured matter. A simple design
of the atom, created by Neils Bohr,
looks something like this:
Atoms
• The three particles which make up the atom are:
– Protons
• Found in nuclei
• All atoms have at least one
– Neutrons
• Found in nuclei
• Found in all elements except Hydrogen
– Electrons
• Found orbiting in electron shells (max. of 7) around nuclei
Structure of Atoms
Particle type Found in the…
Charge
Mass (kilograms)
Proton
Nucleus
+1
1.673 x 10-27
Neutron
Nucleus
0 (neutral) 1.675 x 10-27
Electron
Orbiting nucleus
-1
9.109 x 10-31
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Compounds
• Made by the chemical combination of two or
more elements in definite proportions.
– Complex substances
– They are entirely different substances not
just a mix of two or more elements
• Ionic bond - an electron from one atom
transfers to another atom
• Covalent bond - two atoms share
electrons which revolve around
both nuclei
Molecules
The chemical combination of two or more
ATOMS.
- the smallest particle of a compound
that still possesses the characteristics
of the compound.
Basic Rules of Particles
• Shell – the orbital distance the electron is from the
nucleus.
• K-shell – the orbital shell closest to the nucleus. The
shells are named in order K, L, M, N, O, P, Q.
• Maximum number of electrons that can occupy a shell is
found by: 2n2
• Electron Binding Energy – each electron is “bound” to the
nucleus by its own energy level. This is the amount of
energy required to “free” the electron from its orbit.
Measured in electron volts (eV).
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Basic Rules of Particles
• Valence – the number of electrons in the outermost
shell of an atom.
– If an atom gives up an electron in a reaction it is said to
have a positive valence. (protons outnumber electrons)
– If an atom gains an electron in a reaction it is said to have
a negative valence. (electrons outnumber protons)
• Octet Rule – the number of electrons in the outermost shell can
never exceed 8. An atom with 8 electrons in the outer shell is
chemically stable.
• Ionization - the process of turning an atom into an ion.
Occurs
when an electron is added or taken away, changing the electrical
charge of the atom.
Basic Terms of Atomic Theory
• Isotope – a new atom created by the gain or loss of a
neutron.
• Positive Ion – created when an atom loses an electron.
• Negative Ion – created when an atom gains an electron.
• Atomic Mass Unit – (amu) the combined mass of the
particles of an atom.
• Atomic Number – the number of protons in the atom.
• Atomic Mass Number – used in place of amu when
precision is not necessary. Indicates the number of
protons and neutrons in the nucleus
Chemical Shorthand
Atomic mass
number
Atomic number
A
Z
X
Chemical symbol
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Energy
Energy
• The ability to do WORK.
• Measured in electron Volts (eV)
• All types of matter have the ability to change
their form & shape but they need energy to
accomplish this.
• The law of conservation of energy states that
energy is neither created nor destroyed but is
only changed from one form to another
Work
• Work = FORCE x distance an object is
moved
• The term used for the application of
force to an object
• The joule is the derived unit
of measurement of work
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Force
• Force = mass x acceleration
– Because of inertia, force is needed
to start an object moving, and
because of momentum, force is
needed to stop an object that is
already moving.
– Force can be imparted from one
object to another.
Inertia
The property of an object
with mass to resist a change
in its state of motion.
Momentum
• The product of mass & the velocity at
which the mass is moving.
• The law of conservation of momentum
states that momentum resulting from an
object in motion is not lost unless an
outside force acts upon it.
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Types of Energy
• Potential energy – the capacity of an object to do
work based on its position, weight, etc.
• Kinetic energy – the energy of motion.
• Chemical energy – the energy released during a
chemical reaction.
• Electrical energy – the energy of moving electrons
(usually through a wire).
Types of Energy
• Thermal energy – the energy of heat &
motion at the molecular level.
• Nuclear energy – the energy contained in
the nucleus of an atom.
• Electromagnetic energy – the energy of
charged particles manipulated through an
electric current.
The Electromagnetic Spectrum
• Radiowaves – long wavelength,
low frequency.
• Microwaves – shorter wavelength,
slightly higher frequency.
• Infared light – radiant heat.
• Visible light – smallest segment of
spectrum.
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The Electromagnetic Spectrum
• Ultraviolet – causes molecular interactions. Infared,
visible light, & UV light make up a very small section
of the electromagnetic spectrum & are located directly
in the middle of the spectrum.
• X-rays – man-made radiation. The energy level at
which the waves travel is very high.
• Gamma rays – shortest wavelength, highest frequency.
• UV, X, and Gamma are the only EM radiations with
ability to ionize (remove an electron from an atom)
Wave-Particle Duality
• Electromagnetic Radiation has properties of both a
wave and a particle.
- EM travels through space as a wave (a disturbance in
space). They are unique in that no medium is required.
- High end EM acts as a particle in that it has the ability
to ionize.
More on Waves
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Wavelength
• The length of one wave, measured from the
top of one wave to the top of the next
• Wavelength (λ) = velocity (c)/frequency (υ)
λ
Velocity
• How far an object travels in a specified
period of time
• A property common to all EM radiation
• Waves in the electromagnetic
spectrum all travel at the same
velocity, the speed of light (c),
or 3 x 108 m/s
Velocity(c) = frequency(υ)x wavelength(λ)
Frequency
• The number of waves that go by in one
second
• Frequency(υ) = velocity (c)/wavelength(λ)
• Hertz (Hz) is the SI unit of measurement for
frequency
1 sec.
• 1 Hz = 1 cycle/s
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Amplitude
• The distance from peak to valley
• Indicates the intensity (energy) of the wave
Properties of X-rays
• Highly penetrating, invisible rays in the form of
electromagnetic radiation.
• Electrically neutral; electric & magnetic fields do
not affect them.
• Can be produced over a wide variety of energies &
wavelengths.
• Release heat when passing through matter
(thermal transfer).
• Travel in straight lines.
Properties of X-rays
• Travel at the speed of light (3 x 108 m/s).
• Can ionize matter, causing biologic & chemical
changes.
• Cause fluorescence of light sensitive crystals.
• Cannot be focused by a lens (refracted).
• Affect & cause images on photographic film.
• Produce secondary & scatter radiation.
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Radioactivity
• A general term referring to the processes in
which some unstable atoms emit particles &
energy
– “Radiate” from the atom
– Results from atoms with unstable nuclei that
contain too much energy
Radioactivity
• Electromagnetic energy is pure energy, not particles
with mass. Has properties of both electricity &
magnetic energy - travels at the speed of light
– Alpha particles (α) - two protons bound to two neutrons
with no electrons
– Beta particles (β) - tiny particles, similar to electrons, that
form inside the nucleus of an unstable atom - has a negative
charge & is instantly ejected from the positively-charged
nucleus
– Photons - particles of energy that have no mass - Gamma
(γ) rays are streams of photons
Radioactivity & Half-life
• The length of time it takes for half the atoms in an
element to decay
• Half-lives are used to measure the quantity of
radioactivity
– Becquerel is the SI unit to measure radioactive decay - one
decay event/sec.
– Curie is the “old” unit of measure - 37,000,000,000 (3.70 x
1010) nuclei decaying in one second
– 1 Curie = 3.7 x 1010 Bq
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