Construction of X-Ray tube

Oral medicine and Radiology, Dentistry
Components of tube head.
Production of X-rays
Factors controlling the x-ray beam.
Collimation.
Inverse square law.
Stuart. C. White and Michael J. Pharoah

1. CONSTRUCTION OF X-RAY TUBE BY KEERAT KUCKREJA 150301176 1

2. Primary components of X-Ray machine are the x-ray tube and power supply. The tube is often positioned within the tube head. The tube head is supported by an arm which is mounted on a wall A control panel allows the operator to adjust the duration of exposure . The tube current and the tube voltage are usually fixed. 2

3. COMPONENTS OF A TUBE HEAD Tube head showing a recessed X-Ray tube Components of power supply Oil that conducts heat away from the tube Path of useful X-Ray beam from anode An aluminium filter that removes the low energy photons A collimator which restricts the beam size An aiming cylinder 3

4. X RAY TUBE X-RAY TUBE CONSISTS OF AN ANODE A CATHODE EVACUATED GLASS CHAMBER 4

5. CATHODE The cathode consists of A Filament Focusing cup The filament is the source of electrons. It is made up of a coil of tungsten. Filaments also contain 1% thorium which increase the release of electrons from the heated wire 5

6. The filament is mounted between two stiff wires which carry electric current. These two wires connect to both low and high voltage electric sources. The filament is heated to incandescence by flow of current from the low voltage source It emits electrons at a rate proportional to the temperature of the filament known as thermionic emission. 6

7. The filament lies in a focusing cup made up of molybdenum The focusing cup electrostatically focuses the electrons emitted by the filament into a narrow beam directed at a small rectangular area on the anode called as the focal spot. 7

8. ANODE It consists of a tungsten target embedded in a copper stem . The purpose of target is to convert the kinetic energy of the colliding electrons into x-ray photons . Tungsten is used as a target material because of its : High atomic number (74) High melting point (3422 C) High thermal conductivity Low vapor pressure at the woking temperature . 8

9. Focal spot is the area on the target to which the electrons are directed from which x-rays are produced. The target is inclined to about 20 degree known as the angle of truncation to the central ray of x-ray beam. This causes the effective focal spot to be approx. 1mm *1mm as opposed to the actual focal spot which is 1mm*3mm. 9

10. POWER SUPPLY The primary function of power supply are to Provide a low voltage current to heat the filament. Generate high potential difference to accelerate the electrons from cathode to focal spot on anode . 10

11. TUBE CURRENT The filament transformer reduces the voltage of the incoming AC to about 10v in the filament circuit. This voltage is regulated by the filament current control (mA selector) TUBE VOLTAGE The actual voltage used on x-ray machine is adjusted with an autotransformer By using the kilovolt peak selector ,the operator adjusts the autotransformer and converts the primary voltage from input source to a desired secondary voltage. The selected secondary voltage is applied to the high voltage transformer which boosts up the peak voltage to 60,000-1,20,000V which provides electrons sufficient energy to generate x-rays. 11

12. PRODUCTION OF X-RAYS 12

13. FACTORS CONTROLLING THE X-RAY BEAM 1.Tube voltage peak 13

14. 2.Tube current 14

15. 3.Filtration n 15

16. 4.Exposure time 16

17. 5.Collimation 17

18. 6. Inverse square law 18

19. ` Oral Radiology Principles and interpretation – Stuart C. White , Micheal J. Pharoah 19 BIBLIOGRAPHY

20. 20 THANK YOU!