its a simple presentation on different types of xray tubes.

1. X-RAY TUBES
BY
AUGUSTIN PCS

2. CONTENTS
• Introduction
• Types
• Construction of each tubes
• Features of each tube
• Line focus principle & anode heel effect
• Tube rating
• Tube failure
• Care of tube
• Conclusion

3. INTRODUCTION
• A tube is air evacuated device.
• In which the x-rays are produced.
• Characteristics-:
i) produce electrons
ii) attract electron
iii) physical protective casing
iv) radiation protection
• Purpose:
provide x-rays from near source.

4. INTRODUCTION
Requirement:
• Ability to control quality and quantity.
• X-ray emission from desired port
• movement
Basic principle:
• High voltage across anode and cathode
• electrons emitted
• accelerated toward anode
• Interact and produce x-ray.

5. TYPES
• According to the cathode
Two types
• Cold cathode tube(Crookes tube)
• Hot cathode tubes (all other types)
• According to the anode
Three types
• Stationary anode x-ray tube
• Rotating anode x-ray tube
( conventional radiography tubes, mammography tube, grid
control x-ray tube)
• Rotating envelope x-ray tube

6. Crookes Tube

7. Crookes Tube
• Crookes tube
• Historically , x-rays were discovered
radiating from experimental discharge tubes,
called Crookes tube.
• Invented by William Crookes and others.
• Commonly known as cold tubes.
• Used till 1920.

8. Crookes Tube
Consists :
• Tube Envelope
• Anode
• Cathode
• Anti Cathode

9. Tube Envelope
• Consists of a partially evacuated glass bulb .
• Material – sodium or cerium
• Air pressure of 10-6
to 5x10-8
.
Anode
• Material- Platinum
• (At no-78, mp-1768o
c)
Cathode
• Material- Aluminium
(At no -13, mp- 660o
c)
Anti cathode
• Material - Copper plate
CROOKES TUBE

10. Operation
• Field emission or cold emission.
• DC voltage (100kv) across cathode and anode.
• Gas atoms ionized , created positive ion.
• Positive ion attracted to cathode and create more
electron.
• High speed electron strike anode.
CROOKES TUBE

11. Disadvantage
• Unreliable
• Air absorbed by wall, reduces pressure.
• Overheating due to heavy use.
• Intensity and energy of x-ray cannot be
controlled independently.
CROOKES TUBE

12. COOLIDGE TUBE
OR
STATIONARY ANODE TUBE

13. COOLIDGE TUBE
• Crookes tubes improved by William Coolidge in
1913.
• Called Coolidge tube or hot cathode tube.
• Characteristic features-
i) high vacuum
ii) heated filament
Iii) thermionic emission

14. COOLIDGE TUBE
Construction
• Tube envelope
• Anode assembly
• Cathode assembly

15. COOLIDGE TUBE
Tube Envelope
• Spherical tempered glass tube with two cylindrical arms-
cathode and anode arm.
• Made of borosilicate ( Pyrex)
• Internal pressure 10-8
mmHg
• Hold both electrodes

16. Anode assembly
Consists
Target
• Material –tungsten embedded in
copper.
• Thickness- 2-3 mm, Size – 1.8 to 2.2 mm
• Shape – Circular, square or rectangular
• Anode angle – 6-20o
• Typical angle – 16.5o
• High atomic no. – W- 74
• High melting point – W- 3370o
c
• Evaporating point - 5600o
c
COOLIDGE TUBE

17. Cathode assembly
• Focusing cup
• Filament
COOLIDGE TUBE

18. Focusing cup
• Made of molybdenum
• Nickel coated (anticorrosive layer)
• Streamline the thermionic cloud.
Filament
• Made of tungsten
• High melting point-3370o
c
• High evaporation point- 5600o
c
• Highly ductile and malleable
COOLIDGE TUBE

19. COOLIDGE TUBE
Operation
• Cathode filament heated, emits electron.
• Emitted electron accelerated towards
positively charged anode.
• X-ray produced- bremsstrahlung and
characteristic .

20. COOLIDGE TUBE
Advantages
• Stability.
• Intensity and energy of x-ray can be
controlled independently.

21. ROTATING ANODE X-RAY TUBE

22. ROTATING ANODE X-RAY TUBE
• The rotating anode tube is an
improvement of the Coolidge
tube.
Characteristic feature-
i) anode rotates
ii) tungsten – rhenium alloy

23. ROTATING ANODE X-RAY TUBE
Construction
• Glass envelope
• Anode assembly
• Cathode assembly

24. ROTATING ANODE X-RAY TUBE
Glass envelop
• Borosilicate glass
• Supports electrodes
• Shape - cylindrical
• Size - 30 – 50 cm length
20 cm broad
• Thinner window – size 5x5 cm
thickness 0.2mm
• Highly evacuated
• Internal pressure- 10-8
mmHg
• Ceramic metal (adv prevent off
focus radiation)

25. ROTATING ANODE X-RAY TUBE
Anode assembly
 Target track
• Material- 90% tungsten and 10%
rhenium(high thermal capacity, less
roughening)
 Anode disk
Base – molybdenum ( advanced
graphite alloy, light wt and heat
dissipation)
Anode angle- 7-17o
,typical angle – 12o
Rpm- 9000
Shape – beveled

26. • Anode stem
material – molybdenum
thin and long
restrict conduction of heat
• Rotor
material – copper and iron
high thermal capacity and
conductivity
rotation of anode
9000 rpm
Anode stem
ROTATING ANODE X-RAY TUBE

27. • Bearing
• Made of metal balls
• Lubrication – silver powder
• ( adv – liquid gallium
lubricated fluid dynamic
bearing)
• Stator induction Motor
• Material – electromagnet
• Supplied by AC power
ROTATING ANODE X-RAY TUBE

28. • Cathode AssemblyCathode Assembly
• Focusing cupFocusing cup
• Same as in Coolidge's tube.Same as in Coolidge's tube.
• Effectiveness of focusingEffectiveness of focusing
cup depends uponcup depends upon
• Shape , size , applied chargeShape , size , applied charge
and length of filamentand length of filament
ROTATING ANODE X-RAY TUBE

29. • FilamentFilament
• Dual filamentDual filament
• The size varies from 2.2mm toThe size varies from 2.2mm to
7mm in length in small filament7mm in length in small filament
• The size varies from 7mm toThe size varies from 7mm to
15mm in length in large15mm in length in large
filamentfilament
• 99 % tungsten and 1% thorium99 % tungsten and 1% thorium
• (prevent breakage, prevent(prevent breakage, prevent
evaporation)evaporation)
ROTATING ANODE X-RAY TUBE

30. ROTATING ANODE XRAY TUBE
ADVANTAGES
• Provide greater area for bombardment
• Better heat dissipation than stationary
anode tube

31. MAMOGRAPHY X-RAY TUBE
• X-ray tube dedicated for
mammography.
• Characteristic features
I) Low kv
Ii) Characteristic radiation
Iii) High spatial resolution

32. MAMOGRAPHY X-RAY TUBE
• CONSTRUCTION
• GLASS ENVELOPE
• ANODE ASSEMBLY
• CATHODE ASSEMBLY

33. Glass envelope
• Borosilicate glass/ ceramic metal
• Window- berrylium (z=4, mp=1287o
c)
Anode
• Material-
molybdenum – (z=42, mp=2623o
c)
rhodium - (z=45)
• Anode angle (0 or 16)/ tube tilt(24 or 06)
MAMOGRAPHY X-RAY TUBE

34. MAMOGRAPHY X-RAY TUBE
• Cathode assembly
consists
Focusing Cup - Mo
Filament
• W for MO track
• Rh for Rh track
(Added filter – Mo)

35. GRID CONTROLLED XRAY
TUBES
• Used in fluoroscopy units
• Purpose- reduced pt dose
• Interval between exposure.
• Focusing cup functions as a switch.
• Focusing cup act as a third electrode.
• Highly negatively charged -1.5 kV

36. ROTATING ENVELOPE TUBE

37. ROTATING ENVELOPE TUBE
• Most advanced technology till date.
• Idea of rotating envelope – 1917
Characteristic features
• Electron beam is shaped and controlled by
magnetic field.
• Cooling surface of anode in direct contact
with cooling fluid
• And a rotating envelope

38. ROTATING ENVELOPE TUBE
It consists of four system
• Tube envelope system
• Electron emission system
• Magnetic deflection system
• Cooling system

39. ROTATING ENVELOPE TUBE
• Tube envelope system
i. Material – non magnetic stainless steel
ii. Directly Attached to anode disk
iii. Annular/Circular Window (Thickness – 0.2
mm)
iv. Max rotational speed – 150Hz

40. ROTATING ENVELOPE TUBE
• Anode assembly
• Consists
Target track- 90% tungsten & 10% Rhenium
Anode Disk – Tungsten , Zirconium,
molybdenum body(TZM Alloy)
BP- 4612, MP- 2600

41. ROTATING ENVELOPE TUBE
• Electron emission system
Cathode Assembly
Consists
Focusing cup
Flat Emitter
Shape of emitter – circular
Material – tungsten
Thickness -100µm
Diameter - 5µm
Meander like path – for
filament heating .

42. RET
• Magnetic deflection system
Three coils
R- coils - Deflect the beam radial
direction onto focal spot. (flying
focal spot in z- direction,)
Q-coils – focus the beam to
determine the size
Phi- coils – deflection of flying focal
spot in tangential direction

44. ROTATING ENVELOPE TUBE
• Microcontroller
controls individual coil
currents (real time )
Electronically adjusted focal
spot
Best image quality.

45. ROTATING ENVELOPE TUBE
• Cooling system (convective)
Anode disk comes in direct contact with
cooling oil.
Oil rotation is turbine flow
Flow of oil - during exposure is 25ltr/min
- during pump running 8 ltr/min
Oil – Mineral oil

46. • Advantages
• Better heat dissipation.
• Various size multiple focal spot
• Longer tube life.
• can be used in high kV and High mA
technique for prolonged duration ( ie. High
mAs)
ROTATING ENVELOPE TUBE

47. Line focus principle
• Introduced in 1918
• Relation between anode angle and focal
spot
• Three principles
i) Incr anode angle – incr effective focal spot
size ( decr intensity of x-ray beam, poor
image quality)
ii) decr anode angle – decr effective focal spot
size (incr intensity of x-ray beam, better
image quality)
iii)without change in anode angle increasing
the bombarding area incr actual focal
spot ,effective and provide better heat
dissipation.

48. Anode heel effect
• Varying intensity of x-ray
at anode side is lesser
than cathode side.
• Beveled anode absorbs
some x-ray photon

49. TUBE RATING CHART
• Capacity of focal spot
supplied by
manufacture.
• Shows maximum
power delivered for a
given exposure time
without over loading.

50. Tube failure
• Anode pitting.
• Rapid heat increase at
anode.
• Filament vaporization.

51. CARE OF X-RAY TUBE
• Warm up the anode following manufactures
recommendation
• Minimize filament boost (prep) time.
• Use lower tube current (mA).
• Follow rating chart.
• Do not exceed anode thermal capacity or heat
dissipation rate of the target.
• Do not make high mA exposure on cold target.
• Do not rotate the tube housing rapidly from one
position to another

52. Conclusion
Mastery is not about perfection, but a
process ,a journey.
• So lets be sure there is going to be
more advanced technology and there will
be x-ray tubes with better heat dissipation
and lesser patient dose.