2. Atomic structure
• The number of electrons equals the number of proton in
an atom so the atom has no net charge ( electrically
neutral).
• Different materials( gold, lead, copper…etc) will have
different numbers of protons/electrons in their atoms.
However, all the atoms in a given material will have the
same number of electrons and protons.
3. Atomic structure
Atomic number(Z);
• Number of protons in the nucleus of an atom
Neutron number(N);
• Number of neutrons in the nucleus of an atom
Atomic mass number( A);
• Sum of the number of protons and neutrons in an atom
Isotopes
• Atoms with the same atomic number but different
atomic mass
Nucleons
• Proton and neutron together
4. Electrostatic force: Is the attraction between positive
protons and negative electrons. This attraction causes the
electrons to be pulled toward the protons in the nucleus.
In order to keep the electrons from drooping into the
nucleus, the Centrifugal force, pulls the electrons away
from nucleus.
Electrostatic and centrifugal force
6. The amount of energy required to overcome the
electrostatic force to remove an electron from its
orbit. Depends on atomic number (# of protons).
Te higher the atomic number, the higher the
electrostatic force will be for all electrons in that
atom.
Binding Energy
7. Ionization : Ejection of electron from the orbit
(atom gained a positive charge) by energy that is
greater than binding energy of electron.
8. • Excitation; Electrons transferred from high
binding energy level to low binding energy
level ( neutral excited atom) by energy that
is not great enough to make ionization.
9. Radiation
• Is the emission and propagation of energy in the
space and substance in the form of waves or
particles
• Particulate Radiation :Tiny particles of matter
that possess mass and travel in straight lines at
high speeds.
10. The movement of energy through space as a
combination of electric and magnetic fields
oscillating perpendicular to each other and to the
path of traveling .
Examples : x-ray, Radio-wave, Tv-waves, visible
light and gamma ray.
Travel at the speed of light (3 x 108
meters/second) (186,000 miles/second)
Electromagnetic Radiation
11. Electromagnetic radiation
Particle concept:
Radiation travel as a discrete bundles of energy
called photons or quanta with no mass or charge
traveling in the space at the speed of light in
straight lines
Wave concept:
Radiation travel a waves and focuses on the
properties of waves ( velocity, wavelength and
frequency).
14. X-ray Energy
• The energy of a waves of electromagnetic
radiation represents the ability to penetrate an
object.
• The higher the energy, the more easily the wave
will pass through the object.
• The shorter the wavelength and the higher the
frequency the greater the energy will be.
15. X-ray Characteristics
1) High energy waves (short wavelength and high
frequency)
2) No mass
3) No charge (neutral)
4) Travel at speed of light
5) Invisible
6) Travel in straight line
7) Cannot be focused to a point
8) Differentially absorbed by different materials
9) Cause fluorescence to some material
10) Harmful to living tissue
11) Diverges when travel to and through the object.
20. Metal housing :
•is filled with oil which surrounds
the transformers and x-ray tube.
•It ground the high voltage
component and protect the x-ray
tube.
Oil:
1.it insulate the electrical
components.
2.Help to cool the anode
3.Act as a filtration of x-ray.
Tube head seal:
• Prevent the oil from leaking
out of the tubehead but still
allow most x-rays to pass
through
22. X-ray tube components
1.focusing cup: focusing electrons on target ( made of
molybdenum)
2.Filament: release electron when heated.
3.Vacume :
No air or gases inside x-ray tube that might
interact with electrons
Prevent oxidation of tungsten filament
Increase velocity of electrons
4.Target: x-ray produced when electron striking target
5. Copper stem: remove heat from target
6: leaded glass: keeps x-ray from exiting tube in wrong
direction
7: unleaded glass window: it allow x-ray to pass
through
26. Tungsten
( filament and target)
• High atomic number ( 75)
• Transfer head readily
• High melting point
• Can be drown to fine wires
• Lowe vapor pressure.
29. ELECTRICAL CIRCUTES
• The low- voltage circuit: control the heating of
the filament. There are no x-rays produced
during this time.
• The high-voltage circuit: control the flow of
electrons across the x-ray tube. When you
depress the exposure button, the high-voltage is
activated. X-rays are produced until the
exposure time ends.
• The length of time the high-voltage circuit is
operating represents the exposure time.
30.
31.
32. Exposure Button
• The timer determines the length of exposure,
not how the long you hold down the exposure
button.
• You can’t overexpose by holding the exposure
button down for extended period. However, you
can underexpose by releasing the exposure
button too soon (the exposure terminates as soon
as you release the button).
33. milliampere (mA) selector
• Determine the amount of current that
will follow through filament.
• The higher the mA setting, the higher
the temperature of filament, the
greater the electrons that will produced.
36. kiloVolt peak (kVp) control
• kVp Control: regulates the voltage across the x-ray
tube.
• 1 kv ( kilovolts)= 1000 v (volts)
• 70 kvp setting means the peak ( maximum voltage) is
70,000 volts.
• The higher the voltage, the faster the electrons will
travel from the filament to the target.
• The kVpcontrol knob regulate the autotransformer.
42. The smaller the focal spot (target), the sharper
the image (teeth) will be.
The larger the focal spot( target), the higher the
work load capacity.
During x-ray production, a lot of heat is
generated. If the target is too small, it will
overheat and burn up.
In order to get a small focal spot, while
maintaining an adequately large target, the line
focus principle is used.
Line focus principle
43. Line focus principle
• The target is at an angle ( not perpendicular) to the
electron beam from filament.
• Because of this angle, the x-rays that exit through the
PID (appear) to come from a smaller focal spot.
• Even though the actual focal spot( target) size is larger
( to withstand heat buildup), the smaller size of
apparent focal spot provides the sharper image needed
for proper diagnosis.
44. Actual focal spot size: refers to size of the
area on anode target tat is exposed to bombarding
electrons from cathode
Effective focal spot size: refers to focal spot
size as measured directly under the anode target
45. X-ray production
• X-ray production is a very inefficient process.
Only 1% of the interactions between the high
speed electrons and the target atoms result in
x-ray.
• 99% of the interactions result in heat
production.
• There are two types of x-rays produced in the
target of x-ray tube. The majority are called
Bremmstrahlung radiation and others are called
characteristic radiation.
47. X-rays produced when high-speed
electrons from the filament are slowed
down as they :
1) pass close to the nuclei of the target
atoms
2) Strike the nuclei of the target atoms
Bremsstrahlung Radiation
(Braking radiation, general radiation)
50. The energy of the high-speed electron from
the filament must be higher than the binding
energy of the target electron with which it
interacts in order to eject the target electron
X-rays have energies characteristic of
the target material (energy = difference
between binding energies of target
electrons involved, e.g., K & L, K & M, etc.)
Characteristic Radiation
51. K-shell binding energy = 70 keV
L-shell binding energy = 11 keV
M-shell binding energy = 3 keV
Tungsten
54. Heat dissipation
• The excess heat is controlled by :
1. High melting point of tungsten target
2. The conductive properties of the copper sleeve
3. Cooling by oil surrounding the x-ray tube.
• If the target gets too hot, electrons will( boil off) and
accelerate from the target to the filament during the
reverse half of alternating cycle when the target is
negative and the filament is positive.
• Undesired radiation will be produced and the filament
will be damaged by electron bombardment.
55. Heat capacity or tube rating
5 minutes are required after a
single continuous exposure of 17
seconds at 90kVp and 15mA for
adequate heat dissipation before
another exposure is made.
62. Filtration
Low energy x-ray do not contribute to formation of
an x-ray image; all they do is expose the body to
radiation. Therefore, we need to get rid of them.
Filtration increase the average energy ( quality) of
the x-ray beam
Inherent filtration, results from the materials
present in the x-ray machine that the x-rays have to
pass through. These include:
1. Unleaded glass window
2. Oil
3. Tubehead seal
This remove the very week x-ray.
63. Added filtration, removes the x-rays that had
enough energy to get through the inherent filtration
but are still not energetic enough to contribute to
image filtration.
Total filtration: is combined inherent and added
filtration for the x-ray machine.
As a general rule:
If x-ray machine is 70kVp or higher ,total
filtration is equivalent to 2,5 mm aluminum thickness
If x-ray machine is below 70kVp, total filtration is
equivalent to 1.5 mm aluminum thickness
64. Inherent
Glass window
of x-ray tube
Added
Aluminum filter (s)
Total 70 kVp
1.5 mm
2.5 mm
Total Filtration
Oil/Metal
barrier
68. The shape of opening in collimator determines
the shape of the x-ray beam.
The size of the opening determine the size of
the beam at the end of PID.
Longer PID Have a smaller opening in collimator.
Rectangular collimation results in the patient
receiving 55% less radiation when compared to
what they would receive with a round PID.
