Interaction of x-rays with matter

Question 1

attenuation is dependent on;

Answer 1

• Energy of x-ray beam
• Atomic number of absorber
• Thickness of the absorber
• Density

Question 2

Pair production

Answer 2

• High energy x-ray photon escapes interaction with electrons and comes close enough to the nucleus of the atom to be influenced by the strong nuclear field
• Incident of 1.02 MeV or greater interacts with nucleus and it undergoes a change of state, forming 1 positron and 1 electron,
  *They unite and the mass of both particles is converted to energy in theform of annihilation

Question 3

Applications of photoelectric effect

Answer 3

• Bones absorb radiation which is why they appear white
• Soft tissues allow radiation to pass and they appear gray on radiograph
• Air-containing structures the appear completely white

Question 3

Photodisintegration

Answer 3

• An x-ray photon of 10Mev interacts with a nucleus and its absorbed by the nucleus.
• After the nucleus has absorbed the photon it becomes excited and instantly emits a subatomic particle( nuclear fragments) e.g neuton, proton or alpha particle