X ray

X RAY RADIOLOGY

1. X-RAY PHYSICS Dr Girish Gunari Moderator-Dr Madan mohan

2. Content HISTORY X-RAY PRODUCTION X-RAY GENERATORS

3. HISTORY WILLIAM ROTGEAN [ 1895 discovered x ray ] [ 1901- Nobel prize]

4. The first x-ray photograph Roentgen’s wife BERTHA’S hand

5. X-ray = high energy electromagnetic radiation with shorter wavelength [ 0.01-10 nm ] with high penetrating power X-ray properties Travel in straight line

6. Travel at speed of light [3X10’8m/sec or 186400 miles/sec]

7. Electrically neutral Produces ionization Induces fluorescence N

8. PRODUCTION OF X-RAY When fast moving electrons stopped by target material Kinetic energy of electron is converted into Heat-99% X-RAY-1%or <1%

9. Electron interaction with target atom BREMSSTRAHLUNG CHARACTERISTIC X-RAY

10. BREMSSTRAHLUNG/ BRAKING RADITION ON SLOWING DOWN DUE TO ATTRACTIVE FORCE OF NUCLEUS[PROTONS] KENETIC ENERGY OF ELECTRON EMITED AS RADITION

11. Electron which passes closer to the nucleus emit x-ray of higher energy Electron which move little for from the nucleus emits lower energy More kvp more closer electron will reach nucleus

12. Bremsstrahlung will have all possible energy from minimum to maximum Continues spectrum

13. CHARACTERISTIC X-RAY hv = E k -E l E k and E I -binding energy Characteristic radiation are characteristic of k shell of target Increase in atomic number =more energy of inner shell= more is the energy released

14. X-RAY SPECTRUM Continuous bremsstrahlung spectrum Line spectra characteristic of target material and superimposed onto the continuous bremsstrahlung spectrum

15. E= ev e-charge v-velocity (kvp) Different tube voltage v1 > v2 > v3 Increase in voltage increase in energy Emax changes

16. Different tube current i1 > i2 Larger current =larger rate of flow of charges =more electrons arriving per unit time Emax remains same

17. Different target z1 > z2

18. X-RAY TUBE DESIGN CATHODE -electron source ANODE - Target to stop the electron HIGH VOLTAGE- supply to accelerate electron GLASS /METAL ENVOLOPE

19. CATHODE -electron source Is negative terminal of the tube Parts Filament focusing cup Connecting wire – {10 v and 3-5 mas}

20. FILAMENT – is a small coiled wire Commonly made from Thoriated tungsten [molybdenum and rhenium used to increase efficacy] On heating metal its atom absorb thermal energy and some of the electrons in metal escape through surface of metal called THERMIONIC EMMISION

21. WHY?...TUNGSTEN [0.2mm diameter-( spiral 0.2cm 1cm length] High melting point [3370*c] THERMIONIC EMMISION below melting point 2200*c Low vapour presser [long life] can be formed into helical =will have larger area

22. Modern tubes have two filaments Larger filament High current Low resolution Larger focal spot Small filament Low current High resolution Shorter focal spot

23. Tube current – number of electron flowing from cathode to anode It is unidirectional- i.e from cathode to anode

24. FOCUSING CUP Made up of molybdenum or nickel Contains negative charge Designed to focus electron on small area [focal spot]

25. Focusing cup as switch Focusing cup is made more negative 1.5kv compare to filament so that all electron converge at a point [pinched]before reaching target –act as switch to off and on

26. SPACE CHARGE EFFECT Kvp is zero or near zero Emitted electron form cloud around it called space charge [Edison effect] and they tend to repeal electron back into filament called space charge effect On increasing kvp Electron get more Energy and over Come this effect So tube current increases

27. SATURATION VOLTAGE

28. ANODE Positive electrode Made up of 90%tungsten+rhenium alloy { more resistance to surface pitting by heat} TYPES Stationary rotating

29. STATIONARY ANODE Small plate of tungsten 2-3mm thick embedded in copper-for heat dissipation Used in –dental x ray and portable x-ray Anode angle -15-20* Disadvantage- heat dissipation

30. ANODE –placed at an angle 15-20

31. some definitions FOCAL SPOT – area of target where electron are bombarded and x ray are emitted ACTUAL FOCAL SPOT - actual area where electrons are bombarded EFFECTIVE FOCAL SPOT- is length and width of x-ray beam projected

32. Smaller the focal spot –better is the resolution but more heat expose at single small focal spot lead to pitting

33. LINE FOCUS PRINCIPLE Developed to solve PROBLEM- need of large focal spot for heat dissipation and small focal spot to produce good radiographic detail

34. Decreasing the angle decreases effective focal spot size C=B sin0

35. ROTATING ANODE {1933}

36. ROTATING ANODE Made of tungsten alloy with rhenium Has bevelled edge with angle of bevel 6to20* Speed of rotation 3000 rpm[60Hz] -9000[180HZ

37. Stationary anode limited –large heat produced will pit the anode During long period of exposure Rotating anode advantage is –heat is distributed in larger area of anode by rotating it so long period of exposure is done without any damage to anode

38. made up of molybdenum High melting point [2600*] Poor conductor of heat-protect ball bearing from un desirable heat Length should be short as possible (length = inertia= load on bearings Anode stem

39. STATOR OF INDUCTOR COIL Provides magnetic field necessary for induction of current ROTATOR OF INDUCTION COIL the magnetic field provided by stator induces current in copper rotor This current provides power for rotation of anode assembly

40. BALL-BEARINGS Increase life of tube Lubricant used in silver or lead Silver is suitable in vacuum (oil vaporise in heat and vacuum is lost)

41. GENERATORS

42. Faraday’s Experiment No current was induced if the magnet at rest inside or outside the coil.

43. Faraday’s law of electromagnetic induction A change of magnetic flux linked with a conductor induces an electromagnetic force ( emf ) in the conductor

44. The magnitude of the induced emf is proportional to the rate of change of magnetic flux and to the area of the circuit . e- electro magnetic force - change in magnetic flux

45. SELF INDUCTION In a single coil or solenoid, if there is a change in the magnetic flux, an emf will be induced in the same coil. This phenomenon is known as self induction

46. Lenz’s law of electromagnetic induction states that the induced current is always in a direction to oppose the change producing it.

47. MUTUAL INDUCTION When two coils are placed very close to each other, the magneticflux change in one coil induces an emf in other coil. This phenomenonis known as mutual induction

48. A.C Generator mechanical energy is used to rotate the coil to produce electrical energy

49. Fleming’s right-hand

50. 0* 90* 180* 270* 360*

51. Generator Ordinary Generator : Mechanical energy =>Electrical energy X-ray generator device : that supplies electric power to the X-ray tube Electric supply : 220 V, 50Hz, 3 phase, AC power

52. Why does x ray tube require electrical energy ? • To emit electrons from cathode – filament circuit(10V) •To accelerate from cathode to anode - high voltage circuit(40-150kVp) •To regulate the length of exposure - timer circuit

53. Generator Control panel kVp - mA Exposure time Transformer assembly Grounded metal box Low voltage filament transformer High voltage transformer Group of rectifiers -Oil (Insulator)

54. Electric supply : 220 V, 50Hz, 3 phase, AC power •Filament circuit - 10 V High voltage circuit 40-150 kVp

55. Transformer A transformer is a device that either increases or decreases the voltage in a circuit AC DC

56. Laws of transformer The voltage in the two circuits is proportional to the number turns in the two coils Number of turns increases then voltage increases

57. step up transformer -more turns in the secondary coil -

58. step down transformer =fewer turns in the secondary coil

59. Electric supply : 220 V, 50Hz, 3 phase, AC power •Filament circuit - 10 V High voltage circuit 40-150 kVp step up transformer step down transformer

60. principle of conservation of energy increase in voltage must be accompanied by a corresponding decrease in current

61. Autotransformer- self induction

62. Autotransformer Step down transformer(filament ) 10 V -Turns in secondary coil less Step up transformer (cathode to anode) 40-150 kV Turns in secondary coil > 600

63. PROBLEM - Output of Transformers is alternating current(AC ) Cathode – negative Anode-positive Cathode –positive anode -negative

64. SOLUTION: RECTIFY!!!

65. • Rectification is the process of changing the alternating current into direct current Rectifier is the device that allows electrical current in one direction but does not allow current to flow in the other direction

66. Rectifier is a semi conductor. Semiconductor acts like an insulator at low temperature and acts like a conductor at room temperature

67. N-type semiconductors[negative]

68. P-type semiconductors [positive]

69. P-N junction N-type and P-type crystals are joined

70. P N P-N diode conducts current in a forward direction only ,

71. Half wave rectification

72. Advantage: Prevents damage to the tube in inverse cycle.

73. Disadvantage: Half of the power is wasted 25cycle/s

74. Full wave rectification

75. Advantage: Utilizes full electrical potential 50cycle/s

76. PULSED POTENTIAL/SINGLE PHASE GENERATOR X-ray Low energy radiation increases patient dosage Loss of exposure time as x ray are in pulse

77. Three phase generators •Three phase generator consists of three single phase currents out of step with each other by 120*

78. • Supply power at near constant potential

79. Three phase transformers Consists of three sets of primary and secondary windings. • Two types of configurations: Delta Wye (star)

80. Six pulse six rectifier

81. Ripple factor variation in the voltage across the x-ray tube Single phase 100% Triple phase

82. Delta will lag the wye by 30degrees

83. Delta will lag the wye by 30degrees Lag by 30* Twelve pulse

84. Smoothing -capacitor

85. Advantages constant voltage Produces X rays efficiently throughout the exposure. No time is spent in bombarding the X ray tube with low energy electrons. High tube ratings for extremely short exposure times. Produces radiographs with short exposure times and high repetition rates.

86. step down 220v=> 10v Auto transformer Filament circuit

87. Kilo voltage control circuit Auto transformer step up 220 => 40to150

88. Transformer rating • The rating of a transformer states the maximum safe output of its secondary winding , expressed in kilowatts kW = kV x mA 1000

89. Storage generators Capacitor discharge generator Electric supply Step up transformer Large capacitor X-ray tube KV falls during exposure at the rate of 1KV for each mA Advantage : Small and easy to move. Limitations : Must be charged prior to use. Battery powered generator Electric supply Nickel-cadmium battery DC chopper Transformer Rectifier X-ray tube Limitation: Heavy and requires regular battery maintenance. Advantages: Stores considerable energy Independent of power supply

90. DR1==GE wipro - 9 00 MA

91. Room 1 -700MA allengers

92. Room2-500 MA

93. Room 3-IIT 350MA

94. DR-2 600MA

95. Thank you