85. Theoretical and Technical basis of X-ray diagnosticsrename
yaboiemil's version from 2016-02-07 19:13
Section1. X-rays are produced by Bremsstrahlung.
2. X-rays are high energy photons.
3. X-ray images are a result of the absorption and attenuation of these high-energy photons as they pass
through the body, which can be expressed by...
Attenuation of X-rays:
|d||Thickness of absorbing layer|
|micrometer symbol||attenuation coefficient|
|e||base of natural logarithms|
4. The attenuation coefficient will depend on the proton number of the absorbing medium, the energy of
the radiation and the interaction of photons with matter (e.g. photoelectric effect, compton scattering,
electron-positron pair production)
5. The x-ray is made up of 4 main parts:
Source of High Voltage6.Made up of:
|The Transformer||Transforms normal mains voltage into v. high voltage needed for x-ray production|
|Rectifier||Turns AC into DC because X-ray production can only use DC|
|Circuit||Used to smooth out the pulsating DC from the rectifier|
|Mains voltage||230 - 380V|
The X-ray Tube7. Made up of a hot cathode (filament) and a cold anode (tungsten usually)
8. A beam of electrons is accelerated between the hot cathode onto the focus area of the cold anode.
9. This decelerates the electrons very quickly (brehmsstrahlung) causing excess energy to be converted
10. The energy of the electrons incident upon the anode is U.e ...
|U.e||Energy of incident electron upon anode|
|h||Planck's Constant (6.62 x 10^-34 m^2kg/s)|
|Lamda min||Minimum Wavelength|
The Control Panel
11. Contains a voltmeter, ammeter
12. Helps to position patient and machinery
13. The control panel is behind a shield to protect the nurse/assistant
The Mechanical Part
14. Stand to hold the tube
15. Examination table
16. Bucky grid under the patient
17. Film/fluorescent screen under the patient
18. Image intensifier
|Bremsstrahlung||Electromagnetic radiation produced from the deceleration of charged particles.|