- Let’s start this post -Production of X-RAY and their properties
X-ray is produced by an X-ray tube, the three main parts of an x-ray tube are the anode, cathode, and filament
When the filament is heated through the power supply, electrons are ejected from its surface, a high voltage between the cathode and the anode, the force of electrons accelerate towards the cathode to anode, the electrons hitting the anode tungsten target, produce bremsstrahlung radiation only 1 % X-ray produce and 99% electron energy is converted into heat.
- The x-ray beam energies pass through a thin glass window in the tube envelope, in some tube thin glass beryllium window.
1.X-ray tube envelope is generally made of Borosilicate glass (pyrex)
2. The Cathode design – The cathode in a modern x-ray tube (Invented in 1913, W.D.Coolidge ) consists of wire filament to provide current .and negatively charge (-) focusing cup.
- The function of focusing cup is to direct the electron towards the anode, so that it strikes the target in a well define area called the focal spot.
- The size of the focal spot depends on the filament size.
- The diagnostic tube usually has two separate filaments to provide a double focal name one small and large focal.
- Large focal is 2×2 mm may be used for taking high-speed radiograph where large current anode 500 MA and short exposure time required.
- Small focal 1×1 mm is used in fluoroscopy where low current 100 to 200 MA at large exposure time is required through viewing the final detail of the anatomical structure.
- The material of filament is tungsten is chosen because of its high melting point.
3. The Anode design – Target anode is positively charge (+), made of tungsten 90%,rhenium 10% alley because of high atomic number, high melting point, high conductivity & heat capacity that can intense heat produced in the target by electron bombardment.
- Coating layer molybdenum and graphite base because of lightweight resistance to aging, greater heat store capacity, less roughing the target area, and avoiding the crest in the anode.
1.X- rays are high penetrating power.
2.X -rays are electrically neutral and can not be deflected by electric & magnetic field.
3.X-rays can produce fluorescence effects in certain crystals.
4.X-rays effect photographic film & produce a latent image which can be developed chemically.
5.X- rays produce biological & chemical changes.
6 .X-rays travel at the speed of light 3×108m/s.
7.X-rays have ionization power.
8.X-ray, liberate minute amount of heat on passing through matter.
Important fact –
ICRP (60) 1991 recommendation for effective dose –
International commercial radiation protection (ICRP)
- Occupational effective dose 20 mili sv/year (msv)
- (Average cover period of 5 years should not exceed in 30msv/years.)
- Trainees – 6 msv/ year
- Public 1 msv/year
- Lens of eye – 150 msv/year
- Trainees – 50 msv/year
- Skin/hands /feet -500 msv/years
- Trainees – 150 msv/years
- Pregnant lady – 2 msv/years
- Effective dose unite –Sv (sievert) ( earlier REM)
- Absorbed dose unite – gray
- 1 gray=100 rad
- Energy unite- jule
- 1ci (curie)=3.7×1010 becquerel.
- 1 Becquerel =2.7×10-11ci (curie)
- Radio Activity unite – becquerel
- 1ev -1.6×10-19jule
- Radiation is the process by which energy transfer takes place without any medium
- Radiation unite –c/kg
- Ionization radiation – 2.5×10-4c/kg
- KeV- kilo energy volt
- mAs- Milli Ampere Second
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