The effects of radiation on biological tissues

Question 1

What matter can interaction with x-ray

Answer 1

• Classic coherent scattering
• Photoelectric interactions
• Compton scattering
• Pair production
• Photodisintergration

Question 2

Classical (Coherent) Scattering

Answer 2

• Between Low energy X-ray photon and an atom
• Change photon direction (scattered) without loss of energy
• No energy transfer to patient or matter
• No ionization

Question 3

Photoelectric Effect

Answer 3

• Incoming x-ray photon is completely absorbed by collision with inner shell electron
• Secondary radiations were created as a result of Electron Cascade (from outer shells to inner shell)

Question 4

Compton Effect or Compton Scattering (occupational hazard)

Answer 4

• Incoming photon collides with outer-shell electron creating a free Compton electron (recoil) and ion pair)
• Incoming photon loses some of its energy through collision, scatters off in a random direction (scatter angle) and undergoes other interactions until energy is gone
• The electron vacancy is filled nearly instantly through other interaction of PE and Compton

Question 5

Photodisintegration

Answer 5

the process by which the x-ray photon is captured by the nucleus of the atom with the ejection of a particle from the nucleus when all the energy of the x-ray is given to the nucleus.

Question 6

Pair production

Answer 6

Pair production is a process in which a gamma ray of sufficient energy is converted into an electron and a positron

Question 7

Attenuation of x-ray intensity by interaction with matter are?

Answer 7

Coherent scattering
Compton Scattering
Photoelectric absorption

Question 8

X-ray interaction in the body begin through?

Answer 8

atomic level (atoms, molecules, cell, tissue, organ)

Question 9

Two Theories of cellular irradiation damage exit (radiation of cells)

Answer 9

Direct hit theory (genetic damage)
Indirect hit theory (create free radicals)

Question 10

Effect of radiation on a cell

Answer 10

Mutations, cell death, sublethal injury

Question 11

Factors Affecting Radiosensitivity

Answer 11

• Dose (higher dose, higher the effect)
• Dose rate (fractionalized less destructive)
• Oxygen (higher O2 in irradiated cells, the greater is damage due to H2O2 formation)
• Linear Energy Transfer (LET)
• Law of Bergonie and Tribondeau (less mature more sensitive)
• Length and frequency of exposure (Protraction and Fractionation)

Question 12

Physical factors affecting radiosensitivity

Answer 12

Linear Energy Transfer (LET)

Relative Biologic Effectiveness (RBE)
- Compare effects of different electromagnetic photons to produce the identical effect

Oxygen Enhancement Rate (OER)

Question 13

What is Relative Biologic Effectiveness

Answer 13

compare effects of x-rays or gamma rays to any other type of ionizing radiation producing an identical effect.

This is because of the difference in the physical properties of the two types of radiation and their ionization ability

Question 14

What is hormesis

Answer 14

This is a theory that a small dose of radiation may actually be of benefit

Question 15

Radiation Effects Influenced by

Answer 15

• Total dose
• Dose rate
• Total area covered
• Type of tissue
• Age

Question 16

Two types of radiation effects

Answer 16

Stochastic
Non-stochastic

Question 17

Dose-Response Curves

Answer 17

Threshold
- The dose at which effect are produced, below this dose, there is no effect

Non-threshold
- Any dose produces a response

Question 18

Units of Measurements

Answer 18

Roentgen
- Measure exposure in air

Radiation absorbed dose
- Measure the amount of energy absorbed in any medium

radiation equivalent man

Curie
- Measures the activity of a radioactive material