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Radiation biology and safety > Introduction and Radiation Review > Flashcards

Introduction and Radiation Review Flashcards

1
Q

Angiography

A
  • The radiographic visualisation of blood vessels after injection of a radio opaque contrast
  • Help people who have blockages to the heart by inserting a permanent stent to hold the blood vessel open

May be

  • Diagnostic
  • Interventional
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2
Q

Radiation Protection (ICRP)

A
  • Legislation and regulations are guided by recommendations from the International Commission on Radiological Protection
  • Give the ‘official’ scientific view of the effects of radiation on people and so laws are written around their content
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3
Q

Radiation Protection (ARPANSA)

A
  • Australian Radiation Protection and Nuclear Safety Authority
  • Most of the QLD regulations are based on the ARPANSA regulations and codes
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4
Q

Deterministic Effect

A
  • Most organs/tissues are unaffected by the loss of even a large number of cells
  • When the number lost becomes large enough there is observable damage or loss of function
  • Probability of causing observable damage or loss of function will be zero at small doses but rise rapidly (to 100%) above threshold dose
  • Above the threshold, the severity of the damage will also increase with dose
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5
Q

Stochastic (Random) Effects

A
  • As a result of exposure to IR, a cell is modified but still left viable and able to divide

There is a period in which:

  • The probability that the effect will occur increases with dose
  • The severity is not affected by the magnitude of the dose
  • Examples include the induction of cancer and genetic effects
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6
Q

Recommendations for limiting exposure to IR are designed to:

A
  • Prevent deterministic effects

- Keep the probability of stochastic effects from exceeding an acceptable level

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7
Q

Isotope

A

Nuclides with the same Z but different A

Same number of Protons but different number of Neutrons

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8
Q

Alpha Decay

A

Emission of a He particle from the nucleus

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9
Q

Beta Decay

A

Emission of an anti-neutrino and the conversion of a neutron to a proton

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10
Q

Positron Decay

A

Emission of a neutrino and the conversion of a proton to a neutron

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11
Q

Gamma Rays

A
  • Emitted following nuclear decays due to changes in nucleon configuration
  • A nucleus in an unstable, high energy state can decay to a lower energy state
  • Excess energy is emitted
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12
Q

X-Rays

A
  • Emitted following a change in the state of the atom (e.g., in particular the electron structure)
  • Usually following ionisation, when an outer electron may fill the vacancy, the excess energy is emitted as an X-ray
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13
Q

Photon Interactions with Matter

A
  • Photoelectric Effect
  • Compton Scattering
  • Pair Production
  • Coherent Scattering
  • Photonuclear Disintegration
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14
Q

Energy Loss Processes - Photons

A
  • Photons penetrating matter will be attenuated via the 3 interaction processes
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15
Q

Intensity - Mew

A
  • Is difficult to calculate so known features are obtained from experimental measurements
  • Increases rapidly with atomic number
  • Decreases rapidly with photon energy
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16
Q

Energy Loss Processes - Electrons/Positrons

A

Some expected properties of electron interactions:

  • Large angular deflection due to similar masses (range is defined as the linear distance penetrated into material)
  • Large kinetic energy transfer in collisions
  • Large changes in direction and magnitude in velocity
17
Q

Types of Ionising Radiation

A

Particulate
- Alpha and beta particles

Electromagnetic
- X rays and gamma rays

18
Q

LET

A

Linear Energy Transfer refers to the amount of energy locally transferred to the material per unit path length of the IR

19
Q

LET Radiations

A

Low LET Radiation
- x ray, gamma ray, electrons, beta particles

Medium to High LET Radiations
- Protons, neutrons and alpha particles

20
Q

Interaction of Medium/High LET radiations with Matter: Neutrons

A
  • Neutron are unchanged so they cannot interact via coulomb forces
  • They deposit most of their energy in biological tissue by knocking on protons from water molecules
  • These ‘knock on protons’ being moving charged particles then cause ionisation and gradually slow down in the material
  • Hence the biological effect of neutrons and of protons is similar (for the same amount of energy deposited in tissue)
21
Q

Interaction of Medium/High LET radiations with Matter: Alpha Particles and Protons

A
  • Interact mainly with the atomic electrons and gradually slow down in the material
  • They have a short range and high LET
22
Q

Interaction of Low LET radiations with Matter: Electrons and Beta Particles

A
  • These are electrically charged, so they interact by coulomb forces primarily with atomic electrons but occassionally with a nucleus
  • When they interact with an atomic electron they lose energy and slow down
  • Generally they move on to produce further ionisations
  • The net effect is that each incident electron or beta-particle produces many
    ionisations, losing energy (slowing) on each occasion until it stops in the
    material
23
Q

Interaction of Low LET radiations with Matter: Photons

A

Interact with matter primarily by:

  • The photoelectric effect
  • Compton scattering
  • Pair Production
  • These moving electrons behave as do incident electrons interacting with matter via the coloumb forces
  • These coulomb interactions cause ionisation and excitation of the material and the moving electrons gradually slow down and stop
24
Q

Dose

A
  • When IR transfers energy to matter the energy transferred is quantified as Dose
  • There is a quantity ‘exposure’ which is also sometimes incorrectly called dose
25
Q

Exposure

A
  • Applies to x rays and gamma rays only and is a measure of the flux (number) of photons
  • It is ‘that quantity of x or gamma radiation that produces in air, ions carrying 1 coulomb of charge per kg of air
26
Q

Absorbed Dose

A
  • This is the fundamental dose unit in radiation protection
  • Expresses the energy absorbed per unit mass as a result of exposure to IR
  • ‘The energy imparted by the IR per unit mass of matter’
27
Q

Equivalent Dose

A
  • For the same absorbed dose, the biological effects of IR depend on the type and energy
  • The equivalent dose is a weighted dose
  • With the weighting factor determined by the type and energy of the radiation to which the organ or tissue is exposed
28
Q

Effective Dose

A
  • A variation of the response of different tissues to radiation
  • Need to apply a tissue weighting factor to the equivalent dose
29
Q

Tissue Weighting Factor

A
  • Represents the relative contribution of that organ or tissue to the total detriment due to effects resulting from uniform irradiation of the whole body
  • Vary with the population of exposed individuals
30
Q

Equivalent and Effective Doses

A
  • Desirable that a uniform equivalent dose over the whole body should numerically be the same as the effective dose
  • Achieved by setting the tissue weighting factors
  • Factors are chosen to be independent of the type and energy of radiation
  • It is desirbale that a uniform equivalent dose over the whole body should give an effective dose equal to that uniform equivalent dose
  • Hence, an effective dose of 1mSv has the same risk whether the equivalent dose was delivered to the thyroid or to the the lung or to the total body
31
Q

Committed Effective Dose

A
  • External Radiation Exposure

- Internal Radiation Exposure

32
Q

External Radiation Exposure

A
  • Ceases when the source is turned off or when a person moves away from the source
33
Q

Internal Radiation Exposure

A
  • An intake of a radionuclide commits the person to receiving a dose for a period of time which depends on the effective half-life of the radionuclide
34
Q

Committed Equivalent Dose

A

The equivalent dose which an organ or tissue is committed to receive from the intake of radioactive material

35
Q

Committed Effective Dose

A

The effective Dose which a person is committed to receive from the intake of radioactive material

36
Q

Justification

A
  • the justification of a practice
  • no practice shall be adopted unless it produces sufficient benefit to the exposed individuals or to society offset the radiation detriment it causes
37
Q

Optimisation

A

Three considerations

  • The magnitude of doses
  • The number of people exposed
  • The liklihood that potential exposures will be kept ALARA
38
Q

Limitation

A
  • Places limits on the risk to individuals so that risks do no exceed a value which is considered unacceptable for everyday, long term exposure

Radiation biology and safety (5 decks)

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