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BASICS OF RADIATION AND
PRODUCTION OF X-RAYS

Presented byDr. Dinanath Chavan
First year PGT, Department of
Radiodiagnosis...
Radiation
• Radiation is energy that travels through space or matter.
• Two types of radiation used in diagnostic imaging ...
EM RADIATION
• In this type, the energy is "packaged" in small units
known as photons or quanta.
• Visible light, radio wa...
Particulate Radiation
• The other general type of radiation consists of small
particles of matter moving through space at ...
Electromagnetic spectrum
X-rays are electromagnetic radiation of exactly the same nature
as light but of very much shorter...
Electromagnetic radiation is the transport of energy
through space as a combination of electric and magnetic
fields.
Ele...
Properties of electromagnetic
radiation
• Electromagnetic radiation → wavelike
fluctuation of electric and magnetic fields...
Electromagnetic radiation

According to the classical
theory Electromagnetic
radiation can be
considered as wave
motion .
...
Wave concept of electromagnetic radiation
•All EM radiations travel with the speed of light
186000miles/sec, 3×10ˆ8 m/sec ...
Particle concept of electromagnetic radiation
•Short EM waves like XRAYS react with matter as if they are
particles rather...
Relationship between wavelength and
energy
Relationship between wavelength and frequency
ν= c/λ
c – velocity of light (~3×...
X-ray Production
Wilhelm Conrad Roentgen (18451923)

X-rays were first discovered in 1895 by the
German physicist William Roentgen, when us...
Site of discovery
Roentgen's lab where, on 8
November 1895, he noticed an
extraordinary glow while
investigating the behav...
The first x-ray
photograph:
Roentgen’s wife
Bertha’s hand
X-ray tube

Basic elements of an X Ray source assembly
Glass enclosure
•Vacuum: to control the
number and speed of the
accelerated electrons
independently.
• Pyrex glass is used...
Cathode -------•Negative terminal of
the x-ray tube is called
cathode or filament.
•Along with filament 2
other elements :...
CATHODE --------

MADE OF TUNGSTEN + 1%-3% THORIUM ( better emission of electrons. )
Filament and focusing cup
( Nickel )
•

Modern tubes have two
filaments
1. Long One : higher
current/lower
resolution, lar...
Focusing Cup

Cathode assembly of a dual-focus x-ray
tube. The small filament provides a
smaller focal spot and a radiogra...
Focusing cup

Current across
tube one direction
only

Mutual repulsion
↑Number of
electrons

Prevented by focusing cup – f...
Thermionic emission
When Current flows – wire heated

Absorbs thermal energy – electrons move a small
distance from the su...
Thermionic emission

Emission of electrons resulting from the absorption of
thermal energy – thermionic emission
(Tungesto...
Space charge
•Collection of negatively charged electrons in the vicinity
of filament when no voltage applied btw cathode a...
Space charge cloud
Temperature limited

Space charge cloud shield the electric field for tube voltages of 40kvp
and less (...
Tungsten
1.
2.
3.
4.
5.

Thin wire
Strong
High melting point
Less tendency to vaporize
Long life expectancy

Z # 74
MELTIN...
Filament vaporization
•Filament vaporization – shorten the life
•Not heated for too long- filament boosting circuit
•Vapor...
Anode +++++

Stationary anode
Tungsten target in copper anode
Rotating anode+++

Spread the heat produced during an exposure over a large area of
anode – capable of withstanding high t...
Anode +++ parts
1. Anode disk –tungsten
•3600rpm
•Beveled edge – line focus
•Target area increased but
effective focal siz...
Anode +++
Modification of tube to improve speed of rotation and in
turn increased ability to withstand heat .

1.Stem leng...
Focal spot
•True focal spot :Area of the tungsten target (anode)
that is bombarded by electrons from the cathode.
•The siz...
Line focus principle
•Anode angle : defined as
the angle of the target
surface with respect to the
central ray in the x-ra...
Line focus principle

Foreshortening of the focal spot length
Line focus principle

effective focal length = focal length • sin
Effective focal spot<actual focal spot
Anode angle

Large focal spot = greater heat loading.
Small focal spot = good radiographic detail.
Heel effect
The heel effect: The heel
effect is due to a portion
of the x-ray beam being
absorbed by the anode.
This resul...
Heel effect
Intensity of exposure on
anode side < cathode side
of tube
Heel effect less noticeable
with large focus-film
d...
• The intensity of the x-rays emitted through the heel of
the target is reduced because they have a longer path to
travel ...
Properties of xrays
1.
2.
3.
4.

X-rays travel in straight lines.
X-rays are electrically neutral
X-rays are Polyenergetic...
Properties of x-rays
6. X-rays cannot be deflected by electric field or
magnetic field.
7. X-rays cannot be focused by len...
Processes of x-ray generation
When high speed electrons lose energy in the target
of the x-ray tube

2 processes of xray g...
Degree of deceleration
0.5%time electron
comes in proximity
with nucleus
Coloumbic forces attract
and decelerate the
elect...
Bremsstrahlung ( braking radiation )
Enrgy of photon = enrgy of
initial ectron – enrgy of
braked electron

Energy of photon E = 12.4 /λ
Energy is related to th...
Continuous spectrum

Highest energy determined by the kVp
Minimum wavelength determined by the kVp
Maximum wavelength dete...
Brems radiation- Polyenergetic
Characteristic radiation

Characteristic radiation results when the Electrons bombarding the
target eject electrons from t...
Characteristic X-Ray Production
M Shell

Outgoing projectile electron
(lower energy)

Target atom
L Shell
K shell
Incoming...
Characteristic radiation
BINDING ENERGIES
OF DIFFERENT SHELL ELECTRONS

K-70 KEV
L-11 KEV
M-2 KEV
Characteristic radiation
L

K

M

K

(β)70-2 = 68 keV

L

11-2 = 9 keV

M

(α)70-11= 59 keV

Between 80 and 150 kVp , k sh...
Characteristic radiation

THERE ARE MANY
CHARACTERISTIC RADIATION
PRODUCED IN ONE ATOM
THEREFORE CHARACTERISTIC
RADIATION
...
Characteristic radiation

Less Polyenergetic
Typical x-ray pattern
Factors affecting x- ray spectrum:1) Effect of tube current (mA) (while others
remain constant):
 More mA more e- s flow ...
2)Effect of kV ( other factors remaining constant)
-> As kV is raised area under the curve increased
-> The position of th...
3)Effect of added filtration: ( other factors remaining
constant)
-> Added filtration absorbs low energy x-rays and allow
...
Super Rolatix ceramic x-ray tube
Metal casing instead of glass envelope.
Three ceramic insulators – two insulators for the...
Advantages of Metal -• less off focus Radiation .
• higher tube loading.
• longer tube life with high tube currents.
Cooli...
Super Rolatix ceramic x-ray tube
Thank you
Basics of radiation and production of x rays
Basics of radiation and production of x rays
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Basics of radiation and production of x rays

  1. 1. BASICS OF RADIATION AND PRODUCTION OF X-RAYS Presented byDr. Dinanath Chavan First year PGT, Department of Radiodiagnosis SMCH. ModeratorDr. Mrinal Dey Professor, Department of Radiodiagnosis SMCH.
  2. 2. Radiation • Radiation is energy that travels through space or matter. • Two types of radiation used in diagnostic imaging are 1. electromagnetic (EM) and 2. particulate. Electromagnetic Radiation • EM radiation includes: (a) gamma rays, (b) x-rays, (c) visible light, (d) radiofrequency
  3. 3. EM RADIATION • In this type, the energy is "packaged" in small units known as photons or quanta. • Visible light, radio waves, and x-rays are different types of EM radiation. • EM radiation has no mass, is unaffected by either electrical or magnetic fields, and has a constant speed in a given medium. • EM radiation travels in straight lines; however, its trajectory can be altered by interaction with matter. • EM radiation is characterized by wavelength (λ), frequency (v), and energy per photon (E)
  4. 4. Particulate Radiation • The other general type of radiation consists of small particles of matter moving through space at a very high velocity. • Particle radiation differs from electromagnetic radiation in that the particles consist of matter and have mass. • Particle radiation is generally not used as an imaging radiation because of its low tissue penetration. • ex. Electron, alfa particles.
  5. 5. Electromagnetic spectrum X-rays are electromagnetic radiation of exactly the same nature as light but of very much shorter wavelength Unit of measurement in x-ray region is Å and nm. 1 Å = 10-10 m, 1 nm = 10 Å = 10-9 m X-ray wavelengths are in the range 0.5 – 2.5 Å. Wavelength of visible light ~ 3900 - 7500 Å.
  6. 6. Electromagnetic radiation is the transport of energy through space as a combination of electric and magnetic fields. Electromagnetic ( EM ) radiation is produced by a charge ( charged particle ) being accelerated . { electrons are consider as standing waves around the nucleus and therefore do not represent acclerating charges. } Any accelerating charge not bound to atom will emit EM radiation .
  7. 7. Properties of electromagnetic radiation • Electromagnetic radiation → wavelike fluctuation of electric and magnetic fields set up in space by oscillating electrons
  8. 8. Electromagnetic radiation According to the classical theory Electromagnetic radiation can be considered as wave motion . According to the quantum theory electromagnetic radiation can also be considered as a particles called photons
  9. 9. Wave concept of electromagnetic radiation •All EM radiations travel with the speed of light 186000miles/sec, 3×10ˆ8 m/sec but they differ in wavelength •Wavelength (λ) – distance between 2 successive crests / trough •Frequency (ν) – number of crests /cycle per second (Hz) • (λ) wavelength ↓ (ν) frequency ↑ •EM travel with the speed of light c , c=λν •Wave concept of EMR explains why radiation may be reflected , refracted, diffracted and polarized . If each wave has length λ and ν waves pass a given point in unit time velocity of wave is v = λ× ν
  10. 10. Particle concept of electromagnetic radiation •Short EM waves like XRAYS react with matter as if they are particles rather than waves. •These particles are discrete bundles of energy and each bundle is called quantum /photon. •Photon travel at the speed of light. •Amount of energy carried by each photon depends on frequency of radiation. •If frequency doubled energy doubled . •Particle concept can explain the interaction with matter like photoelectric and Compton effect . Energy calculated E=hν h= Planck's constant (4.13×10 ˆ-18 Kev sec )
  11. 11. Relationship between wavelength and energy Relationship between wavelength and frequency ν= c/λ c – velocity of light (~3×108 m/s) also E= hν Instead of ν E =hc/λ ( h×c = 12.4) E= 12.4/λ •Energy of photon =ev •X-ray measured in kilo ev , 1Kev = 1000 ev
  12. 12. X-ray Production
  13. 13. Wilhelm Conrad Roentgen (18451923) X-rays were first discovered in 1895 by the German physicist William Roentgen, when using a Crookes tube He called them ‘x’ rays, ‘x’ for ‘unknown’.
  14. 14. Site of discovery Roentgen's lab where, on 8 November 1895, he noticed an extraordinary glow while investigating the behavior of light outside a shrouded cathode tube. To his astonishment, he saw the shadows of the bones of his hand when held between the tube and a fluorescent screen. Within two months he had published a carefully reasoned description of his work and the famous radiograph of his wife's hand.
  15. 15. The first x-ray photograph: Roentgen’s wife Bertha’s hand
  16. 16. X-ray tube Basic elements of an X Ray source assembly
  17. 17. Glass enclosure •Vacuum: to control the number and speed of the accelerated electrons independently. • Pyrex glass is used.
  18. 18. Cathode -------•Negative terminal of the x-ray tube is called cathode or filament. •Along with filament 2 other elements : connecting wires and focusing cup Filament made of tungsten wire 0.2 mm diameter coiled to form a vertical spiral 0.2 cm diameter and 1 cm length
  19. 19. CATHODE -------- MADE OF TUNGSTEN + 1%-3% THORIUM ( better emission of electrons. )
  20. 20. Filament and focusing cup ( Nickel ) • Modern tubes have two filaments 1. Long One : higher current/lower resolution, larger exposure 2. Short One : lower current/higher resolution. Focusing cup maintained At one point only one at same negative potential is used as the filament .
  21. 21. Focusing Cup Cathode assembly of a dual-focus x-ray tube. The small filament provides a smaller focal spot and a radiograph with greater detail, provided that the patient does not move. The larger filament is used for high-intensity exposures of short duration. 1: long tungsten filament 2 : short tungsten filament 3 : real size cathode
  22. 22. Focusing cup Current across tube one direction only Mutual repulsion ↑Number of electrons Prevented by focusing cup – forces the electron stream to converge on the anode in required shape and size Electron stream spread out Bombarding Large area of anode
  23. 23. Thermionic emission When Current flows – wire heated Absorbs thermal energy – electrons move a small distance from the surface of metal This escape is referred to as thermionic emission
  24. 24. Thermionic emission Emission of electrons resulting from the absorption of thermal energy – thermionic emission (Tungeston heated >22000C) Electron cloud surrounding the filament produced by thermionic emission is termed “Edison effect”
  25. 25. Space charge •Collection of negatively charged electrons in the vicinity of filament when no voltage applied btw cathode and anode – space charge •Number of electrons in space charge remain constant •Tendency of space charge to limit the emission of more electrons from the filament is called space charge effect Filament current →filament temperature →rate of thermionic emission
  26. 26. Space charge cloud Temperature limited Space charge cloud shield the electric field for tube voltages of 40kvp and less ( space charge limited ) , above 40kvp space charge cloud is overcome by voltage applied
  27. 27. Tungsten 1. 2. 3. 4. 5. Thin wire Strong High melting point Less tendency to vaporize Long life expectancy Z # 74 MELTING POINT- 3,370 DEG. CELSIUS
  28. 28. Filament vaporization •Filament vaporization – shorten the life •Not heated for too long- filament boosting circuit •Vaporized filament usually deposited on the inner surface of glass wall •Color deepens as the tube ages- bronze colored “sunburn” •Tends to increase filtration and changes the quality of beam
  29. 29. Anode +++++ Stationary anode Tungsten target in copper anode
  30. 30. Rotating anode+++ Spread the heat produced during an exposure over a large area of anode – capable of withstanding high temperature of large exposures
  31. 31. Anode +++ parts 1. Anode disk –tungsten •3600rpm •Beveled edge – line focus •Target area increased but effective focal size remains the same. 2. Stator 3. Rotor 4. Bearings - metallic lubricants (silver ) 5. Stem - molybdenum 90%tungsten W and 10 % rhenium Re- ↑resistance to surface roughening - ↑thermal capacity
  32. 32. Anode +++ Modification of tube to improve speed of rotation and in turn increased ability to withstand heat . 1.Stem length 2.Bearings 3.weight • As short as possible • Decrease inertia • 2 sets as far as possible • Decrease weight ( molybdenum + W Re alloy ) • Reduced inertia
  33. 33. Focal spot •True focal spot :Area of the tungsten target (anode) that is bombarded by electrons from the cathode. •The size and shape of focal spot is determined by the size and shape of the electron stream which hits the target. •Heat uniformly distributed on focal spot
  34. 34. Line focus principle •Anode angle : defined as the angle of the target surface with respect to the central ray in the x-ray field. •Anode angle range :6°- 20° •Line focus principle Effective focal spot size is the length and width of the focal spot projected down the central ray in the x-ray field .
  35. 35. Line focus principle Foreshortening of the focal spot length
  36. 36. Line focus principle effective focal length = focal length • sin Effective focal spot<actual focal spot
  37. 37. Anode angle Large focal spot = greater heat loading. Small focal spot = good radiographic detail.
  38. 38. Heel effect The heel effect: The heel effect is due to a portion of the x-ray beam being absorbed by the anode. This results in an x-ray beam that is less intense on the anode side and more intense on the cathode side. The heel effect is more pronounced with steeper anode angles.
  39. 39. Heel effect Intensity of exposure on anode side < cathode side of tube Heel effect less noticeable with large focus-film distance Heel effect is less with smaller films Cathode ←Intensity→ Anode
  40. 40. • The intensity of the x-rays emitted through the heel of the target is reduced because they have a longer path to travel in the target. The diff in intensity is as much as 45% Factors affecting the heel effect: 1. Anode angle: the steeper the target → ↑↑ heel effect. 2. FFD: ↑↑ FFD → ↓↓ heel effect "with fixed film size". 3. Film size: ↓↓ film size → ↓↓ heel effect "with fixed FFD". 4. Roughening of the target surface → ↓↓ X-rays output & ↑↑ the heel effect. • In radiographs of body parts of different thicknesses → the thicker parts should be placed toward the cathode (filament) side of the x-ray tube. • e.g. AP film of the thoracic spine → anode end over the upper thoracic spine where the body is less thick & the cathode end of the tube is over the lower thoracic spine where thicker body structures will receive the increased exposure.
  41. 41. Properties of xrays 1. 2. 3. 4. X-rays travel in straight lines. X-rays are electrically neutral X-rays are Polyenergetic and heterogeneous X-rays travel at the speed of light electromagnetic radiation 5. X-rays are highly penetrating , invisible rays.
  42. 42. Properties of x-rays 6. X-rays cannot be deflected by electric field or magnetic field. 7. X-rays cannot be focused by lens. 8. Photographic film is blackened by X-rays. 9. Fluorescent materials glow when X-rays are directed at them. 10. Produce chemical and biologic changes by ionization and excitation. 11. Liberate minute amounts of energies while passing through matter. 12. X-rays interact with matter produce photoelectric and Compton effect.
  43. 43. Processes of x-ray generation When high speed electrons lose energy in the target of the x-ray tube 2 processes of xray generation General Characteristic General radiation ( Bremsstrahlung) • High speed electrons with nucleus of the tungsten atom Characteristic radiation • High sped electrons with the electrons in the shell of tungsten atoms
  44. 44. Degree of deceleration 0.5%time electron comes in proximity with nucleus Coloumbic forces attract and decelerate the electron Loss of kinetic energy and change in trajectory e‾ + e‾ +
  45. 45. Bremsstrahlung ( braking radiation )
  46. 46. Enrgy of photon = enrgy of initial ectron – enrgy of braked electron Energy of photon E = 12.4 /λ Energy is related to the potential difference across tube or λmin = 12.4 / kVp
  47. 47. Continuous spectrum Highest energy determined by the kVp Minimum wavelength determined by the kVp Maximum wavelength determined by the filters used
  48. 48. Brems radiation- Polyenergetic
  49. 49. Characteristic radiation Characteristic radiation results when the Electrons bombarding the target eject electrons from the inner orbits of target atoms
  50. 50. Characteristic X-Ray Production M Shell Outgoing projectile electron (lower energy) Target atom L Shell K shell Incoming projectile electron (high energy) W K X-ray L X-ray Characteristic X-ray emission Ejected electron ionizes atom
  51. 51. Characteristic radiation BINDING ENERGIES OF DIFFERENT SHELL ELECTRONS K-70 KEV L-11 KEV M-2 KEV
  52. 52. Characteristic radiation L K M K (β)70-2 = 68 keV L 11-2 = 9 keV M (α)70-11= 59 keV Between 80 and 150 kVp , k shell characteristic contributes to about 10 %(80kVp) to 28%(150kVp) of useful beam.
  53. 53. Characteristic radiation THERE ARE MANY CHARACTERISTIC RADIATION PRODUCED IN ONE ATOM THEREFORE CHARACTERISTIC RADIATION IS ALSO POLYENERGETIC !
  54. 54. Characteristic radiation Less Polyenergetic
  55. 55. Typical x-ray pattern
  56. 56. Factors affecting x- ray spectrum:1) Effect of tube current (mA) (while others remain constant):  More mA more e- s flow from cathode to anode  Change in mA is directly proportional to the change in the amplitude of the x-ray spectrum  Shape of the curve remain unchanged The effect on the tube spectrum when the mA has been halved.
  57. 57. 2)Effect of kV ( other factors remaining constant) -> As kV is raised area under the curve increased -> The position of the curve has been shifted to the right to the high energy side -> The increase is relatively greater for high energy x-ray than for low energy x-ray -> Characteristic curve doesn't change position The effect on the tube spectrum when the kV has been reduced from 80 kV to 70 kV.
  58. 58. 3)Effect of added filtration: ( other factors remaining constant) -> Added filtration absorbs low energy x-rays and allow high energy x-rays to pass through. -> The curve is shifted. The bremsstrahlung emission spectrum is reduced more on left than on right. ->effect of added filtration is the increase in the effective energy of the x-ray beam (high quality) -> Characteristic curve doesn't change position The effect on the tube spectrum when filtration has been added to the exit beam.
  59. 59. Super Rolatix ceramic x-ray tube Metal casing instead of glass envelope. Three ceramic insulators – two insulators for the two high voltage cables, and one supports the anode stem. • Allows more compact tube design. • Most common - Aluminium oxide. Anode rotates on an axle which has bearings at each end – provides greater stability and reduce the stress on shaft. • Allows use of massive anode up to 2KG. • larger heat storage capacity. Allows higher mAs settings.
  60. 60. Advantages of Metal -• less off focus Radiation . • higher tube loading. • longer tube life with high tube currents. Cooling – better cooling due to more efficient transfer of heat to the oil through the metal enclosure, as compare to the glass enclosure. ( metal is better conductor of heat )
  61. 61. Super Rolatix ceramic x-ray tube
  62. 62. Thank you

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