1. Principle of radiation
Suppat ittimakin, md.

2. Radiation What is the radiation? Production of radiation
effect of radiation
Radiation protection

3. radiation
emission or transmission of energy in the form of wave or particle through space or through a material medium
Light, heat and sound are also types of radiation
Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particle
Ionizing radiation carries more than 10 ev  enough to ionize atoms and molecule and break chemical bonds

4. X-ray A form of electromagnetic radiation
Discovered by Wilhelm Conrad Röntgen

5. Production of x-ray

6. Production of x-ray Bremsstrahlung
This is radiation given off by the electrons as they are scattered by the strong electric field near the high-Z (proton number) nuclei
Continuous spectrum
Intensity of the x-ray increases linearly with decreasing frequency, from zero at the energy of the incident electrons, the voltage on the x-ray tube

7. Production of x-ray
When a fast moving electron collides with a K-shell electron, the electron in the K-shell is ejected (provided the energy of incident electron is greater than the binding energy of K-shell electron) leaving behind a 'hole'
This hole is filled by an outer shell electron (from the L-shell, M-shell etc) with an emission of a single X-ray photon, called characteristic radiation, with an energy level equivalent to the energy level difference between the outer and inner shell electron involved in the transition.

8. Production of x-ray

9. Production of x-ray
So the resulting output of a tube consists of a continuous bremsstrahlung spectrum falling off to zero at the tube voltage, plus several spikes at the characteristic lines

10. Device for the image production

11. X-ray tube
cathode
anode

12. Collimator
Two collimators: One collimator is placed between the sample and the analyzing crystal and one is placed between the analyzing crystal and the detector
made of lenses or curved mirrors 
narrow the beam of x-ray to a certain area

13. Analyzing crystal
Crystals consist of a periodic arrangement of atoms or molecules 
When parallel x-rays (x-ray photons) strike a pair of parallel lattice planes, every atom within the planes acts as a scattering center and emits a secondary wave

14. Detector
two main types of detectors are used wavelength dispersive XRF spectrometers: the gas proportional counter and the scintillation counter
Change into images

15. Effect of the radiation

16. Effect of the radiation to cells
act directly on the cellular component molecules or indirectly on water molecules
resulting in breakage of chemical bonds or oxidation
Breaking of the DNA
misrepairs of the dna induction of mutations, chromosome aberrations, or cell death

17. Tolerance dose for each organ

18. Radiation safety

21. RSNA 2013: Understanding the Importance of Dose Evaluation and Reporting

25. As Low As Reasonably Achievable
Radiation safety
ALARA
As Low As Reasonably Achievable

26. ALARA
a radiation safety principle for minimizing radiation doses and releases of radioactive materials by employing all reasonable methods
every radiation dose of any magnitude can produce some level of detrimental effects which may be manifested as an increased risk of genetic mutations and cancer

27. ALARA
1) Awareness of potential radiation hazards, exposure levels and safety controls in their work areas 2) Awareness of operating and emergency procedures
3) Awareness of practices that do not seem to follow the ALARA philosophy
4) Compliance with wearing personnel dosimetry and ensuring it’s return to the RSD at the proper exchange frequency

28. Radiation exposure Factors
Time: The less time you spend exposed to radiation the lower your dose
Distance: Like most other physical phenomena, radiation decreases with distance in accordance with the inverse square law
Shielding: Every shielding material has a "halving thickness."  the thickness required to reduce the radiation intensity by half
So if the halving thickness of a material is 1 inch, then a 1 inch thick sheet will cut the radiation to 50%. Two inches will cut the radiation to 25%, 3 inches to 12.5%, and so forth.

29. Radiation exposure Factors (cont)
Traditionally lead is used for shielding  because it has a very low halving thickness (0.4 inches)

30. Shielding???

31. Personal shielding

32. Structure shielding

33. Radiation with pregnancy
Licensees are required to attempt to prevent pregnant workers from exceeding ~ 55 millirem during any one month.
The desire is to avoid a large dose to the fetus during the 8th to the 15th weeks of the pregnancy as this is the period during which it is most sensitive to potential radiation-induced effects
Thus, it is incumbent upon the pregnant employee to strongly consider officially notifying the Radiation Safety Division as soon as she is aware of her pregnancy.

35. references
Radiation safety manual; stanford university (revise march 2010)
Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure. N Engl J Med. 2007;357:2277–2284
Radiology ACo. Appropriateness criteria, 2004–2001. American College of Radiology Web site
RSNA 2013: Understanding the Importance of Dose Evaluation and Reporting

36. Thank you for your attention