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ODDR Medical Physics > Medical Physics 2 - Radiation protection > Flashcards

Medical Physics 2 - Radiation protection Flashcards

1
Q

What is radiation?

A

Radiation is energy. It can be transmitted in waves or as particles.

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2
Q

Name some natural sources of ionising radiation

A
  1. Cosmic Radiation

2. Food E.g. bananas

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3
Q

What is ionisation?

A

A type of incoming radiation that has enough energy to cause an electron to be ejected

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4
Q

What are the 3 different types of ionising radiation?

A
  1. Alpha
  2. Beta
  3. Gamma and x rays
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5
Q

Name some manmade sources of ionising radiation

A
  1. Medical like x rays, therapy nuclear medicine

2. Nuclear atmospheric tests

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6
Q

What is the average total radiation dose per person in the uk?

A

2.7mSv

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7
Q

Name the 4 different radiation units

A
  1. Absorbed dose
  2. Equivalent dose
  3. Dose-rate
  4. Effective dose
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8
Q

What is the absorbed dose?

A

Energy absorbed per unit mass from any type of ionising radiation

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9
Q

What is the absorbed dose measured in?

A

Gray(Gy)= J/Kg

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10
Q

What do we use the absorbed dose for?

What is the equivalent dose?

A

To specify the amount of radiation dose entering the skin surface

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11
Q

What is the equivalent dose?

A

Dose showing the damage causing capability of radiation

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12
Q

What is the equivalent dose red rived from?

A

The absorbed dose but also takes the radiation weighting facto into account for the type of radiation

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13
Q

How do we calculate the equivalent dose?

A

The absorbed dose x radiation factor

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14
Q

Why don’t we use the absorbed dose to judge the damage that radiation causes?

A

Because it does not distinguish the way in which energy is deposited in matter
Ie Alpha particles deposit energy in a very short distance whereas X-rays deposit energy over an extended path

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15
Q

What is the photon weighting factor?

A

1

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16
Q

What is the equivalent dose of X-rays and gamma rays?

A

The weighting factor & equivalent dose of x-rays & gamma rays are the same
So 1

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17
Q

What does the effective dose give us an idea of?

A

gives an idea on the effectiveness on radiation in causing damage to human tissue

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18
Q

What is the effective dose derived from?

A

Derived from the equivalent dose but takes into account the tissue weighting fact that adjust for radiosensitivity of different tissues

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19
Q

How duo we calculate the effective dose?

A

Total equivalent dose x the tissue weighting factor

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20
Q

What do the majority of people think about the dangers associated with radiographs?

A

The effect of radiation is roughly proportional to the dose received, so all radiation doses are potentially harmful

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21
Q

What is the dose rate and what do we use it for?

A

How quickly we accumulate a dose

We use it more for looking at doses in the environment or doses over time

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22
Q

Which of the 4 radiation units do we use to judge radiation risk?

A

Effective dose

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23
Q

Give some examples of how we use radiation to saves lives?

A
  1. Radiotherapy
  2. Early diagnosis
  3. Sterilisation of Blood products, Foodstuffs and Dressings
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24
Q

How can radiation cause harm?

A

It can cause:

  1. Cancer
  2. Cataracts
  3. Skin darkening / burns
  4. Hair falling out
  5. Sterility
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25
What are the 3 ways x-rays interact with tissues?
They can be: 1. Transmitted 2. Scattered 3. Absorbed
26
What do transmitted x rays help us to from?
The image we want to see
27
When are cells at risk of damage the most?
During the replication stage of the cell cycle
28
Which type of cell active or inactive is more sensitive to radiation?
Active cells are more sensitive to radiation
29
Who is more sensitive to radiation adults or children and why?
Children as they are growing so more of their cells are replicating
30
What are cells lately composed of?
Water
31
What can X-rays cause?
Ionisation
32
What can the ionisation of cellular water
can lead to molecular changes and the formation of chemicals that can damage chromosomes This leads to changes in the structure and function of the cell
33
What can ionising radiation lead to in cells?
1. Death 2. Recovery 3. Dysfunctional
34
What is the effect ionisation radiation has on the body dependent on?
1. Dose and doserate 2. Area irradiated 3. Sensitivity of organs/individual irradiated
35
What are the 2 types of radiation effects?
1. Deterministic (acute effects) | 2. Stochastic (chronic, potential long term effects)
36
When does a deterministic radiation effect occur?
If someone is exposed to high doses over a short period of time Only occurs above a certain threshold dose
37
What can increase the severity of a deterministic radiation effect?
Severity increases with dose &dose-rate
38
What are some symptoms of a deterministic radiation effect?
``` Effects include “radiation sickness”, erythema epilation loss of fertility, death Skin reddening Temporary hair loss Ulceration ```
39
When does a Stochastic radiation effect occur?
Occur at high and low doses | Occur randomly, but probability of effect depends on dose received
40
Which of the 2 types of radiation effect may occur in dental radiology?
Stochastic radiation effect
41
Name the different models we can use to estimate the risk
1. Linear threshold 2. Quadratic 3. Wasted dose 4. Hormesis 5. LINEAR NO THRESHOLD
42
What can Stochastic radiation effect cause?
1. Cancer | 2. Can cause harm to future generations
43
When is a risk 'acceptable' to a patient?
Risk acceptable if the individual understands the risk and enjoys some commensurate benefit
44
What is the 'acceptable' risk of death statistic in most communities?
risks of 1 in 100,000 per year or less
45
What risk does 1mSv of radiation pose?
1 in 20,000 risk of developing fatal cancer
46
What 3 things are taken into consideration tomato sure x rays are administrated safely?
1. Limitation: Doses must not exceed the ICRP recommended limits 2. Justification: Benefit must outweigh risk 3. Optimisation: Doses must Beas low as reasonably practicable
47
What is the annual ICRP effective dose limit for employees?
20 mSv
48
What is the annual ICRP effective dose limit for trainees under 18?
6 mSv
49
What is the annual ICRP effective dose limit for members of the public?
1 mSv
50
What is the risk to an adult dental patients of developing cancer when having an intra oral exam?
less than 1 in 6 million
51
What is the risk to an adult dental patients of developing cancer when having an OPT exam?
Less than 1 in 4 million
52
What is the risk to a child dental patients of developing cancer when having an intra oral exam?
Less than 1 in 20 million
53
What is the risk to a child dental patients of developing cancer when having an OPT exam?
Less than 1 in 4 million
54
What do dose limits aim to do?
1. Avoid deterministic effects completely | 2. Reduce the risks of stochastic effects to an “acceptable” level
55
What is the annual ICRP dose limit to the lens of the eye for employees?
20 mSv
56
What is the annual ICRP dose limit to the lens of the eye for trainees under 18?
15 mSv
57
What is the annual ICRP dose limit to the lens of the eye for members of the public?
15 mSv
58
What is the annual ICRP dose limit to the skin for employees?
500 mSv
59
What is the annual ICRP dose limit to the skin for trainees under 18?
150 mSv
60
What is the annual ICRP dose limit to the skin for members of the public?
50 mSv
61
What is the ICRP dose rate for pregnant women?
o Employer must ensure under 1 mSv will be exceeded during declared time
62
What is the dose limit for medical and dental patients ?
No dose limit for patients but justification for the dose is requires

ODDR Medical Physics (3 decks)

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