12. RADIATION HEALTH EFFECTS: DIFFERENT TYPES OF DOSES Flashcards
1
Q
- What is the largest man-made source of radiation exposure to the general population?
A
- the radiation exposure from diagnostic X-Rays
2
Q
- How much does man-made radiation exposure contribute to the total annual exposure from all sources?
A
- 14%
3
Q
- What is the downfall to diagnostic X-Rays?
A
- they provide many benefits
- the use of them does involve a small risk of developing
cancer - the more exposure one receives makes this probability
higher
4
Q
- What was the traditional method of measuring the amount of Ionisation in the air?
A
- Exposure
- this measured the ratio of the total charge produced in
a small volume of air - the total charge was usually in reference to the
electrons
5
Q
- What is the Unit of Exposure for air?
A
- Coulombs per kilogram of air
- Charge/ kilogram
- C/kg
NB:
- the new unit is the Röntgen
- 1R = 2.58 x 10⎺⁴ C/kg
6
Q
- What does the method of Exposure only apply to?
A
- X Radiation (Photons)
- Y Radiation (Gamma Photons)
7
Q
- Which concept is now used more widely as a measure of Radiation damage rather than Exposure?
A
- the concept of an Absorbed Dose
- this is related to the Equivalent and the Effective Dose
8
Q
- What is the SI Unit for the Absorbed Dose?
A
- the Gray
- Gy
- this is the equivalent to the absorption of one joule of
energy in a kilogram of a substance - ionising energy is absorbed in this case
9
Q
- The Gray is a large unit, what are the more common subunits to use for normal radiation protection purposes?
A
- Microgray
- µGy
- this is one millionth of a Gray
- Gy x 10⎺⁶
- Milligray
- mGY
- this is one thousandth of a Gray
- Gy x 10⎺³
10
Q
- What happens when a photon beam reacts with a Medium?
A
- the photon interactions release electrons with Kinetic
Energy - they release them into the medium
- this is known as KERMA
11
Q
- What is KERMA?
A
- this is an acronym for:
Kinetic Energy Released In Medium
(per unit mass)
12
Q
- What happens with the energy that is deposited by these released electrons?
A
- the energy deposited by these electrons per unit mass is the Absorbed Dose
13
Q
- What is the Unit for Kerma?
A
- the Joule Per Kilogram
- the Gray (Gy)
- this is the same as for the Absorbed Dose
14
Q
- How is the KERMA dose different than the absorbed dose?
A
- it is different at high energies
- this includes energies up to 1 MeV
- the KERMA and the Absorbed doses are roughly equal
at low energies
15
Q
- What is the Vital difference between KERMA and the Absorbed Dose?
A
KERMA
- this is the energy released
THE ABSORBED DOSE
- this is the energy absorbed
16
Q
- What is the Equivalent dose?
A
- this is the dose that allows for the effect of Radiation
Exposure on human tissue to be determined
17
Q
- What does the Equivalent Dose relate?
A
- it relates the Absorbed Dose in human tissue
TO THE Effective Biological Damage of the Radiation
18
Q
- What can be said about the relation between Radiation and biological Effects?
A
- different types of radiation have different biological
effects - even if they have the same amount of absorbed dose
19
Q
- What is the SI Unit of the Equivalent Dose?
A
- the Sievert (Sv)
- it represents the Stochastic Biological Effect
- EG: cancer
20
Q
- The Sievert is a large unit, what other modifications of it do we use for Normal radiation Protection levels?
A
- MicroSievert
- µSv
- this is one millionth of a Sievert
- Sv x 10⎺⁶ - MilliSievert
- mSv
- this is one thousandth of a Sievert
- Sv x 10⎺³
21
Q
- How do you determine the Equivalent Dose?
A
- we multiply the Absorbed Dose (Gy)
BY a Radiation Weighting Factor (WR) - this weighting factor is unique to the type Radiation
22
Q
- What does the Weighting Factor (WR) take into account?
A
- some kinds of radiation are more dangerous to
biological tissue
23
Q
- How do we determine the dose in Sieverts (Sv) from the dose in Grays (Gy)?
A
- we multiple by the Wr
- the Wr approximates what would be a very
complicated calculation - the values for Wr will change periodically according to
the ICRP
24
Q
- What affects the intensity of the Exposure?
A
- the more Sieverts that are absorbed in a unit of time
will increase the intensity of the exposure
25
Q
- How do we express Exposure?
A
- we express it as an amount over a specific time period
- this is also known as the Dose Rate
- EG: 5 mSv per year
26
Q
- What does the Probability of a harmful effect from Radiation Exposure depend on?
A
- it depends on the part/parts of the body that are
exposed to the radiation - this is because some organs are more sensitive to
radiation than others - a tissue weighting factor is used to take this into
account
27
Q
- What is more dense: skin or bone marrow?
A
- Bone Marrow
- it will sustain more damage from Radiation Exposure
28
Q
- How do we find out the Effective Dose of an organ?
A
- we multiply the Equivalent Dose of an organ
BY THE tissue weighting factor for that organ
29
Q
- What is the SI unit for the Effective Dose?
A
- the Sievert (Sv)
30
Q
- Does this diagram make sense?
A
- yes
NB:
- the higher the number:
the more sensitive the bone/muscle/organ are
31
Q
- Does this summary make sense?
A
- yes
