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Medrad 1 (RADI1221) > M1 Topic 2: What is radiation? > Flashcards

M1 Topic 2: What is radiation? Flashcards

1
Q

What is radiation

A

Energy that travels as a wave

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2
Q

What is energy

A

Move or change, ability to do work in environment

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3
Q

Kinetic energy (movement)

A
  • Mechanical > motion
  • Thermal > heat (particles)
  • Electrical > movement of current
  • Magnetic > energy that creates push or pull
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4
Q

Potential (stored) energy

A
  • Chemical > food or fuel
  • Elastic > stretched objects
  • Gravity > objects above earth’s surface
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5
Q

Law of conservation of energy

A

Energy cannot be created or destroyed; it can only be transformed from one form to another

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6
Q

Waves

A

Travelling disturbances that transport energy from one location to another

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7
Q

Medium

A

The material the wave travels through

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8
Q

Propagation

A

The movement of the energy

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9
Q

Features of a wave

A
  • Crest (Peak)
  • Trough
  • Amplitude
  • Wave length (period)
  • Distance
  • Rest position
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10
Q

Frequency

A

Number of waves that pass a fixed point per unit time (measured in hertz)

Formula = wave speed / wavelength

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11
Q

What is everything made up of

A

Individual atoms

Molecules = groups of atoms

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12
Q

Structure of atoms

A

Nucleus = protons (+) and neutrons (0), with overall +ve charge

Electrons (-) that surround/orbit nucleus

  • Electrons in inner shell = more strongly bound due to physical proximity

Most atoms have equal amounts of electrons and protons

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13
Q

Sub-atomic forces

A

Hold together protons, neutrons and electrons within an atom

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14
Q

Chemical bonds

A

Hold together molecules (groups of atoms)

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15
Q

Intermolecular forces

A

Hold atoms and molecules together in matter

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16
Q

Excitation reaction

A

Caused by addition of energy to atom/molecule

  • Electrons in atom/molecule absorb energy, can overcome the sub-atomic forces holding them near nucleus, allowing them to move into orbiting path further from nucleus
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17
Q

Instability of excited atoms

A

Unstable in higher energy state

Tend to release energy back into their surroundings via…

  • Transferal of energy to another nearby molecule/atom
  • Emitting the energy as low energy radiation
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18
Q

Relaxation reaction

A

Process of returning to an unenergised/ground state

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19
Q

Luminescence

A

In correct conditions, the emitted radiation from relaxation can have the same frequency as visible light, allowing emission to be seen by the human eye

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20
Q

Ionising radiation

A

When energy completely breaks sub-atomic forces, allowing electron to leave the atom/molecule altogether, leaving behind an ion

  • Most dangerous form of radiation

Disrupts atomic and molecular structure of material

  • Includes DNA and other vital molecules
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21
Q

What is an ion?

A

Describes atom or molecule with unequal number of protons and electrons and therefore carries an overall +ve or -ve charge

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22
Q

Units of ionisation

A

Exposure (number of ionisation events occurring in 1kg of air)

  • Coulomb (C) / kg

Absorbed dose (amount of energy deposited in 1 kg of matter)

  • Gray (J) / kg
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23
Q

Types of medical radiation

A
  • Acoustic radiation > sound energy transmitted via vibration
  • Electromagnetic radiation > energy transmitted via an electric and magnetic field
  • Particulate radiation > energy transmitted as particles
24
Q

Acoustic radiation

A

Propagates/transmits energy by vibrating atoms and molecules

  • Relies on vibrations of atoms making up the medium that wave is passing through
  • Cannot travel thru vacuum where there aren’t any atoms/molecules present to vibrate

Compressions (bunching)
Rarefactions (spreading)

Below 20 Hz = infrasound
Above 20000 Hz = ultrasound

Doesn’t carry enough energy to ionise

25
Electromagnetic radiation (EMR)
Waves of synchronised electric and magnetic fields moving at 90 degrees to one another Energy carried by these waves from small packets on energy called photons that are transmitted in direction of transverse wave
26
Transverse wave
2 waves move across the propagation path of a resulting electro-magnetic field
27
Wave-particle duality
Photons exhibit both wave-like and particle-like properties
28
Examples of EMR
- Microwaves - Infrared - Ultraviolet - X-rays - Gamma (y)-rays
29
Particulate radiation
Includes sub-atomic particles that have had electrons removed from their outer shells to make them +vely charged ions
30
Usefulness of particulate radiation
Highly ionising particles are useful as generally... - Least penetrating - Allows for doses delivered exclusively to targeted area w/o harming nearby healthy tissues
31
Phenomena of types of medrad
Acoustic = mechanical energy (push pull) EMR = Electronic & magnetic fields 90 degrees to each other Particulate = sub-atomic particles or heavy ions
32
Features of types of medrad
Acoustic = compression & rarefaction of atoms molecules EMR = photons (wave-particle duality) Particulate = mass and charge
33
Medium for types of medrad
Acoustic = required EMR and particulate = not required > can travel through vacuum
34
Types of medrad effect on matter
Acoustic = non-ionising EMR = ranges from non-ionising to ionising depending on wavelength Particulate = ionising
35
Linear energy transfer (LET)
Indicates differences in penetration and ionisation capabilities between various types of ionising radiation Measured in electron volts (eV) - 1 Joule = 6.242 x 10^18 eV Formula = amount of energy transferred / distance travelled
36
What is penetration
How far into the material the radiation can travel before it transfers (or deposits) all its energy
37
What is ionisation?
Describes how easy it is for radiation to break sub-atomic bonds
38
What is high LET radiation more useful for?
Therapy (travel less, deposit more energy)
39
What is low LET radiation more useful for?
Diagnostic purposes (travel further, less ionisation)
40
Where does radiation come from?
All around us Natural radiation = entire body Medical radiation = portion of body
41
Radiation weighting factor (Wr)
Considers radiation type on scale from 1-20 1 = radiation behaves like photons 20 = most damaging
42
Tissue weighting factor (Wt)
Considers who different tissues respond to radiation and probability of damage occurring ranging from 0.01-0.20
43
Measuring the effect of radiation on biological material
Absorbed dose x Wr (equivalent dose) x Wt (effective dose)
44
Average background radiation exposure in AUS
1.5-2 mSv per year
45
Average medical exposure in AUS
0.8 mSv per year
46
Sources of med rad
- Electrically generated using machines (can be switched off) - Radioactive elements that undergo radioactive decay (always emitting radiation)
47
Radioactive decay
Radioactive elements are atoms with unstable nucleus due to unbalanced proton/neutron ratio, resulting in too much energy Number of neutrons = atomic mass - atomic number
48
What is an isotope
Atomic number doesn't change, but atomic mass changes - Atoms always have same no. of protons, number of neutrons change
49
How do radioactive atoms get rid of energy
- Emitting it as EMR in the form of gamma rays - Converting some of energy into mass and emitting these masses as particulate radiation
50
What is a half-life?
Time it takes for half of radioactive sample to decay into stable form
51
Radioactive decay formula
delta N = -ve lambda N delta t t = time passed lambda = In(2) / half-life
52
Who is reponsible for the regulation of radiation in AUS
Radiation safety and protection is governed by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA)
53
What does ARPANSA govern
Medical facilities - X-ray departments - Dental clinics Non-medical facilities - Baggage x-ray units - Nuclear reactor research facilities
54
3 key principles of ARPANSA's code of practice
Justification - exposure only if benefits outweigh risks Optimisation - keeping radiation exposures as low as reasonably achievable (ALARA) Limitation - ensure procedures do not exceed safe dose limits for works, patients and any other members of the public
55
ARPANSA responsibilities
- Maintains register of all radiation-related incidents in AUS - Ensures radiation workers must wear personal monitoring devices to ensure exposure is kept below minimum safe limits (no more that 20 mSv each year, averaged over 5-year periods)
56
How can radiation exposure be reduced?
- Minimise duration - Move away from the source - Barriers/shielding into path of source

Medrad 1 (RADI1221) (10 decks)

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