Radiation (1 - 3)

• Binding energy is the amount of energy required to hold the electron in its shell or to remove it

  
  

  The larger the atom, the larger the positive charge in the nucleus, the more tightly bound the inner k shell electrons will be.

  
  

  more energy to remove them from the atom
• What radiation is this

  Characteristic Radiation

  
• What radiation is thing

  Bremsstrahlung radiation

  
• 1. Incident electron collides with orbiting electron in k shell
  2. Incident electron changes direction and orbital electron in ejected
  3. Electron from L ir M shell drops to K shell and emits extra energy as an xray photon (or multiple photons)

  Characteristic Radiation
• Charateristic radiation only occurs at 69.5keV
• 1. Incoming electron passes by very closely with nucleus of atom
  2. Nucleus is positively charged so electron changes direction, and loses energy in form of xray photon
  3. This loss of energy causes the electron to slow down

  Bremsstrahlung Radiation
• The reduction of intensity of the xray beam before it hits the image detector

  Attenuation
• The process where energy is converted from a wave of light to kinetic energy to move and electron out of its orbit around a nucleus

  Absorption
• The process where the original path of the incident photo is changed

  Scattering
• What is this

  A) photoelectric absorption

  
• •An incident PHOTON interacts with an atom within the body tissue of the patient

  •The INNER K SHELL electron is struck by the incident PHOTON

  •ALL the energy is absorbed by the struck electron

  •It is transformed into a PHOTOELECTRON and leaves its orbit

  •The L SHELL electron ‘jumps’ down to fill the vacancy left by the K SHELL electron

  •This transition and energy change creates a LOW energy secondary PHOTON of radiation which is absorbed by the patient

  Photoelectric Absorption
• what what what

  Pair production

  
• Process is not used in diagnostic imaging but rather in radiotherapy

  pair production
• •An incident PHOTON of at least 1.02 MeV (Mega electron Volts) strikes the nucleus of a target atom

  •The PHOTON is transformed and ALL its energy is transferred to an ELECTRON and a POSITRON equally at 0.51 MeV each

  •Both POSITRON and ELECTRON go on to have further interactions with other atoms

  •The ELECTRON is quickly absorbed into another atom’s orbital shell

  •As the POSITRON comes to rest, it combines with a neighbouring ELECTRON and the two particles neutralize each other in a process called ANNIHILATION

  •The particles are converted back into two photons of electromagnetic radiation with 0.51 MeV each and travel away from each other at 180⁰

  Pair production
• Pair Production

  •An incident photon of at least 1.02MeV (Mega electron Volts) strikes the nucleus of a target atom

  •The photon is transformed and all its energy is transferred to an electron and a positron equally at 0.51 MeV each

  •Both positron and electron go on to have further interactions with other atoms

  •The electron is quickly absorbed into another atom’s orbital shell

  •As the positron comes to rest, it combines with a neighbouring electron and the two particles neutralize each other in a process called annihilation

  •The particles are converted back into two photons of electromagnetic radiation with 0.51 MeV each and travel away from each other at 180⁰
• Photoelectric Absorption

  1. An incident photon interacts with an atom within the body tissue of the patient
  2. The inner K shell electron is struck by incident photon
  3. All the energy is absorbed by the struck electron
  4. It is transformed into a photoelectron and leaves its orbit
  5. The L shell electron 'jumps' down to fill the vacancy left by the K shel electron
  6. This transition and energy change creates a low energy secondary photon of radiation which is absorbed by the patient
• huh huh huh

  A) Compton Scatter radiation

  
• 1. An incident photon interacts with an atom within the body tissue of the patient
  2. The outer shell electron is struck the incident photon
  3. Half the energy is absorbed by the struck electron which is ejected by recoil at 45 degrees
  4. The original photon is now scattered inthe opposite 45 degrees angle witht he devreased energy and a longer wavelength and is now known as ___

  Compton scatter photon
• Compton scatter photon

  1. An incident photon interacts with an atom within the body tissue of the patient
  2. The outer shell electron is struck the incident photon
  3. Half the energy is absorbed by the struck electron which is ejected by recoil at 45 degrees
  4. The original photon is now scattered inthe opposite 45 degrees angle witht he decreased energy and a longer wavelength and is now known as CSP
• To minimise effect of compton scatter radiation what can be used?

  Grid
• this is. s

  Classical

  
• 1. An incident phton travels towards ana tom within the body tissue of the patient
  2. It does not have the required energy to eject any orbiting electrons
  3. the incident photon is itself scattered in another direction instead
  4. the atom is not ionised in the process

  Classical
• 1. An incident photon travels towards ana tom within the body tissue of the patient
  2. It does not have the required energy to eject any orbiting electrons
  3. the incident photon is itself scattered in another direction instead
  4. the atom is not ionised in the process

  Classical
• what is radiolysis

  occurs when radiation beam with sufficient energy is directed at living tissue within the body. Reaction happens with water molecules within cells

  Hydrogen atom is removed and the remaining atomic structure is hydroxyl radical
• What is free radical

  it is created when electrons are removed from the atom.

  radicals wants to stabilise and take electron to fill their vacancies and will damage any molecules they come into contact with
• what can free radical damage

  DNA

  Protein

  Cell membrane
• What is Linear Energy Transfer? (LET)

  The rate at which energy is deposited by charged particles as they travel through matter
• Why is Linear energy transfer important?

  it tells us how much energy radiation deposits along its path through tissue, which directly affects;

  Low LET: less energy deposited, more spread out = less localized damage

  • Xrays and gamma rays

  High LET: more energy deposited per unit length = more damage to cells and DNA in a concentrated area.

  • Proton and alpha particles