The x ray beam

x ray beam

4. X RAY TUBE

7. Functions of protective housing
Prevent leakage of radiation
Prevent accidental electric shock
Mechanical support to the x ray tube

8. CATHODE ASSEMBLY

10. Filaments are usually made of thoriated
tungsten because
1.Its melting point is very high
2.Does not vaporize easily

11. ANODE
Common anode materials are
Copper
molybdenum
graphite

12. ANODE ASSEMBLY

14. STATIONARY ANODE
ROTATING ANODE

16. ROTATING VS STATIONARY
ANODE
Rotating anodes let you have higher tube
current and shorter exposure times.
Rotating anodes are powered by induction
motors.

17. INDUCTION MOTOR

18. Tungsten is used as target material because of
atomic number is high (74) make good x-ray
production.
Thermal Conductivity is very good in
tungsten.
High Melting point for tungsten, 3400C.

19. FOCAL SPOT
This is where the high-voltage electrons hit
the anode.

22. Line-focus Principle
the process of making the angle between the
anode surface and the central ray of the X-ray
beam such that the effective focal spot size is
made small as compared to the actual focal
spot size.

24. Heel Effect
Reduction of the X-ray intensity at the anode
side of an X-ray field. In an X-ray field it can
be observed that the film density is lower on
the anode side than on the cathode side. This
phenomenon is termed the heel effect

28. space charge
The excess of electrons or ions in a given
volume.

29. Space Charge Effect
When a low voltage is applied across the
tube, the current is small due to space charge
effects.
 The electron cloud surrounding the filament
has a tendency to repel other electrons back
to the filament unless sufficient accelerating
voltage is applied to pull them away from the
filament as fast as they are produced.

30. With increasing kV, the effects of space
charge are gradually overcome and the
current (mA) increases until all electrons that
are released at the filament reach the anode.

32. X RAY TUBE FAILURE
1.Tungsten target (anode) pitting
2.Bearing failures/glass envelope breaking
3.Heat
4.Filament failure
5.arcing

33. A.) The vaporized tungsten from both filament
and anode.
B.) Breaking of the filament itself.
C.) Holding the rotor switch prior to making
exposures
D.) Single excessive exposures exceeding tube
limits.
E.) Long exposure times.

34. Open Filament
It is the condition where in the filament wire
becomes thinner and eventually breaks. The
excessive heating of the filament causes the
filament to vaporize. Occurs due to
prolonged periods of high mA operation.

35. Arcing
It is a sustained luminous discharge of
electricity across a gap in a circuit or between
electrodes.

36. Methods of heat transfer
Radiation - transfer of heat through emission
of infared radiation.
Conduction - transfer of energy by contact.
Convection - transfer of heat by movement of
heated air, oil from one place to another.
HEAT IS THE MOST IMPORTANT CAUSE OF
TUBE FAILURE

37. VOLTAGE RECTIFICATION
Process of converting AC into DC

38. Half wave rectification

39. Shortcomings of half wave
Waste of supply
Increase exposure time

40. Full wave rectification

41. Diods
A diode is a device which only allows current
to flow through it in one direction. In this
direction, the diode is said to be 'forward-
biased'

42. During the positive half
cycle of input voltage,
the diode is forward
biased and it conducts
for all volts which is
greater than its barrier
potential.
During negative half of
the cycle, the diode is
reverse biased hence it
does not conduct

43. Q. What will happen if unrectified current is
passed through x ray tube?

44. Bremsstrahlung Radiation
When an electron is propelled towards the
nucleus of an atom, its velocity increases then
decreases as it moves away from the nucleus
due to electrostatic attraction of positively
charged protons in the nucleus.

45. The energy of the E= mc
2
has a continuous
spectrum up to a maximum equal to the
maximum kinetic energy of the electron.
 The production of Bremsstrahlung radiation
increases with the atomic number of the
target atom; thus, it increases electrostatic
attraction

48. Characteristic Radiation
The second method of X-Ray production is by
orbital electron transitions.
Characteristic X-Rays are emitted at specific
energies dependent on the type of target
material.

49. High energy electrons interact with an
electron in an inner orbital shell and if the
energy is high enough may eject that
electron, producing a vacancy in the inner
orbital shell.

50. The vacancy is filled by an outer orbital
electron, the excess energy is emitted as an
X-Ray with discrete energy equal to the
difference between the energy states of the
inner and outer electron shell

54. X-RAY Tube Output
The combined output of Bremsstrahlung and
Characteristic X-Rays results in an X-Ray
spectrum

55. X RAY INTERACTION WITH MATTER
The higher the energy of the x-ray, the
shorter the wavelength.
Low energy x-rays interact with whole atoms.
Moderate energy x-rays interact with
electrons.
High energy x-rays interact with the nuclei.

56. Five forms of x-ray Interactions
Classical or Coherent Scattering
Compton Effect
Photoelectric Effect
Pair production
Photodisintegration

57. Two Forms of X-ray Interactions Important to
Diagnostic X-ray
Compton Effect
Photoelectric Effect

58. Changes in X-Ray Beam Quality
and Quantity
An increase in: Results in:
Current (mAs) Increase in quantity
Voltage (kVp) Increase in quantity and quality
Added Filtration decrease in quantity, increase in
quality
Increased target Z increase in quantity and quality
Increased voltage ripple decrease in quantity and quality

59. BRAIN STORMING SESSION

60. 1.When filtration is added to an x-ray tube,
radiation__________ increases
2.The quality of the x-ray beam is controlled by
the ...
3.Filtration is added to the x-ray beam in order
to remove___________x-rays.
4.The unit of measurement for the patient
absorbed dose is the---------------

61. 5.The wavelength of a bremsstrahlung x-ray is
_________ proportional to it's frequency.
6.As the atomic number of an atom increases,
the chances of a photoelectric effect
occurring ------------
7. A _____________ interaction involves a
photon collision with a loosely bound
electron and formation of a scattered photon

62. 8.___________________ must be known in order to
calculate the energy of the x-ray photon
9.Adding filtration is sometimes called
_______________________the beam.
10What versus what is used to plot the x-ray
emission spectrum?
11.The target of an x-ray tube is often made from:
Balsa wood
Cobalt
Tungsten
Aluminum

63. 12.What are the two types of radiation?
Particulate and electromagnetic
Alpha and Beta
Alpha and Gamma
Positive and negative
13.Who discovered natural radioactivity?
Wilhelm Roentgen
Marie Curie
Henri Becquerel
None of the above

64. 13.The primary risk from occupational radiation
exposure is the increased risk of:
Cancer
Blindness
Abrasions
None of the above

65. 2
3
4
5
1

66. THANKS