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Chapter 3 & 4

Rad protection review

The life journey of an X-Ray photon:1. X-ray photon is created at the surface of the anode.2. Primary photons are the photons leaving the tube housing before they interact with matter.3. Once the primary photons enter matter they may be either absorbed, scattered, or pass through without any interaction.




1. Coherent Scatter: low energy photons, less than 10 eV, causes atom to vibrate, no by product at the end. (1-50 kVp) *Not significant in Dx Radiology2. Photoelectric absorption: Occurs 23-150 kVp, photon is either absorbed or reduced depending on energy of the incoming photon and the object's atomic density. By product is a photoelectron, ionized atom and a characteristic photon (sometimes also an Auger electron) This involves an inner shell electron.3. Compton scattering: Occurs 60 kvp - 2 MeV. Incoming photon interacts with an outer shell or loosely bound electron. This electron is freed and and is now called a Compton scattered electron or "recoil electron". The incoming photon loses some of its orginal energy and changes direction. By product: Compton electron and scattered photon. This interaction is NOT depend on atomic (Z) #

Interactions of x-ray & matter:




  1. Exposure: measured in C/kg; used to measure ionization of air
  2. Air Kerma: measured in Grays; measures the kinetic energy deposited in air.
  3. Absorbed Dose: measured in Grays; measures the amount of energy per unit mass aborbed by an object
  4. Equivalent Dose: measured in Sieverts, product of the average dose recieved and the associated radiation weighing factor, ex: EqD = D x Wr. Based on the NCRP report # 116
  5. Effective Dose: measured in Sieverts, product of the the average dose recieved, the associated radiation weighing factor, and the type of tissue. Ex: EfD= D x Wr x Wt
  6. Collective Effective Dose: describes the radiation exposure of a population from low doses of varying radiation sources.
E Example problem: # of people x average EfD
  1. TEDE: Total Effective Dose Equivalent is the sum of the EfD and the Committed Effective Dose Equivalent (CEDE).
**** Read page 68 ***** Important Stuff!!!



  • What does DAP mean?
  • What are some examples of Early Tissue Reactions (p.59)
  • What are some examples of Late Tissue Reactions
  • What does STochastic mean, and name 2 Stochastic effects.
  • Know the Quality Factors for Different types of Ionizing Radiaiton (Wr) p. 65
  • What is LET?

Other super important stuff!!

End ofthe Review!