3. XRAY PRODUCTION

• Type of x-ray produced at the atomic level

  Objective:

  • It happen at the Anode side
  • It does not hit the nucleus interaction, near the nucleus the interaction change spot will release energy called x-ray
• Points to remember:

  • X-ray beam is not a solid beam
  • Electrical energy is converted to x-ray energy (1%) and heat (99%)
  • Millions of high-speed e- interact w/ uncountable number of atoms @ the target
  • The millions of x-rays produced are of different wavelength & energy
• Production of x-ray

  The kinetic energy of e- in the tube current converts to x-ray photons at the focal spot of an x-ray by the formation of Bremstrahlung radiation and Characteristic radiation.
• 2 mechanisms that explain x-ray production at the atomic level:

  1. General radiation
  2. Characteristic radiation
• General Radiation (or Bremstrahlung radiation or Braking radiation)

  • Nucleus is very positive so it push the e- from Cathode out of the atom & changes the direction w/c produce x-ray
  • The incident photon from Cathode does not hit the nucleus, it sudden stop & changed its direction
  • Using 60-90 kVp (60,000-90,000 v)
  • Generation radiation can produce Heterogeneous radiation w/c is a radiation that consisting of different frequencies, various energies, or a variety of particles
• Characteristic radiation:

  • The incident e- from Cathode hit the e- of the Anode and ejected the e- leaving a space / void rearrangement will occur w/c the e- near by will replace then the radiation is produced
  • Only 70 kVp is used
• 1. Primary beam: the x-ray beam produced at the focal spot of Anode & exits from Anode @ the tube head
• 2. Secondary radiation: X-ray produced when the primary beam interacts with matter
• 4. Attenuation: the reduction in the intensity of an x-ray beam as it interacts with atoms of an absorber (loss of energy beam)
• 6. Scattering: a form of attenuation where the x-ray is ejected out of the absorber
• 3. Scatter radiation : type pf secondary radiation that occurs when the x-ray beam deflected from its path due to it interacts w/ matter (change of path)
• 5. Absorption : a form of attenuation where the energy of the x-ray is imparted to the absorber (stay in the matter)
• 3 Possibilities when an x-ray photon interacts with matter

  1. No interaction
  2. Absorption of energy
  3. Scatter of energy
• Factors that affect the amount type of absorption

  1. Energy of x-ray beam
  2. Composition of absorber material
  3. Atomic configuration of absorber material for aprons
• 4 interactions with matter

  1. No interaction

  • No ionization - no scatter - no absorption

  1. Photoelectric effect

  • Phenomenon in w/c e- are emitted from the matter due to their absorption of energy from electromagnetic radiation of very short wavelength (visible light or UV light)
  • e- emitted in this manner may be referred to as “Photoelectron”
  • The energy stay w/in the atom and be absorbed
  • ex. in radiograph; bone appears white because high density, high atomic number caused high absorption
  • Ionization - Absorption - No scatter
• Coherent scattering

  • Also known as Thomson effect or Unmodified scatter
  • Dispersing of low-energy x-rays without the incident photon / x-ray losing its energy
  • Accounts for a practically negligible part of the total interaction between x- rays and matter
  • e- enters outer orbit but does not effected with any e- then it directed out from the atom in different direction
  • No change @ unmodified scatter
  • No ionization – No absorption – ONLY scatter
• Compton scattering

  • Type of scatter that x-rays and gamma rays undergo in matter
  • The Inelastic scattering or Non-coherent scatter of photons in matter results in a decrease in energy of an x- ray or gamma ray photon
  • Energy of the scattered radiation is different from the incident radiation
  • The e- interact with outer orbit electron
  • Involved medium to high form of energy – 62%
  • With Ionization – Absorption – Scatter